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| -rw-r--r-- | doc/ChangeLog | 1 | ||||
| -rw-r--r-- | doc/gawk.info | 1086 | ||||
| -rw-r--r-- | doc/gawk.texi | 189 | ||||
| -rw-r--r-- | doc/gawktexi.in | 183 |
4 files changed, 735 insertions, 724 deletions
diff --git a/doc/ChangeLog b/doc/ChangeLog index bd4ca80c..ba31b052 100644 --- a/doc/ChangeLog +++ b/doc/ChangeLog @@ -1,6 +1,7 @@ 2015-01-25 Arnold D. Robbins <arnold@skeeve.com> * gawktexi.in: Fix a bad URL. And another one. + More O'Reilly fixes. 2015-01-23 Arnold D. Robbins <arnold@skeeve.com> diff --git a/doc/gawk.info b/doc/gawk.info index 2af7b429..59ce5ce6 100644 --- a/doc/gawk.info +++ b/doc/gawk.info @@ -7267,9 +7267,9 @@ value to a variable or a field by using an assignment operator. An expression can serve as a pattern or action statement on its own. Most other kinds of statements contain one or more expressions that specify the data on which to operate. As in other languages, -expressions in `awk' include variables, array references, constants, -and function calls, as well as combinations of these with various -operators. +expressions in `awk' can include variables, array references, +constants, and function calls, as well as combinations of these with +various operators. * Menu: @@ -7288,8 +7288,8 @@ File: gawk.info, Node: Values, Next: All Operators, Up: Expressions ========================================= Expressions are built up from values and the operations performed upon -them. This minor node describes the elementary objects which provide -the values used in expressions. +them. This minor node describes the elementary objects that provide the +values used in expressions. * Menu: @@ -7334,14 +7334,14 @@ the same value: 1.05e+2 1050e-1 - A string constant consists of a sequence of characters enclosed in + A "string constant" consists of a sequence of characters enclosed in double quotation marks. For example: "parrot" represents the string whose contents are `parrot'. Strings in `gawk' can be of any length, and they can contain any of the possible -eight-bit ASCII characters including ASCII NUL (character code zero). +eight-bit ASCII characters, including ASCII NUL (character code zero). Other `awk' implementations may have difficulty with some character codes. @@ -7361,14 +7361,14 @@ File: gawk.info, Node: Nondecimal-numbers, Next: Regexp Constants, Prev: Scal In `awk', all numbers are in decimal (i.e., base 10). Many other programming languages allow you to specify numbers in other bases, often octal (base 8) and hexadecimal (base 16). In octal, the numbers go 0, -1, 2, 3, 4, 5, 6, 7, 10, 11, 12, and so on. Just as `11', in decimal, -is 1 times 10 plus 1, so `11', in octal, is 1 times 8, plus 1. This -equals 9 in decimal. In hexadecimal, there are 16 digits. Because the -everyday decimal number system only has ten digits (`0'-`9'), the -letters `a' through `f' are used to represent the rest. (Case in the -letters is usually irrelevant; hexadecimal `a' and `A' have the same -value.) Thus, `11', in hexadecimal, is 1 times 16 plus 1, which equals -17 in decimal. +1, 2, 3, 4, 5, 6, 7, 10, 11, 12, and so on. Just as `11' in decimal is +1 times 10 plus 1, so `11' in octal is 1 times 8 plus 1. This equals 9 +in decimal. In hexadecimal, there are 16 digits. Because the everyday +decimal number system only has ten digits (`0'-`9'), the letters `a' +through `f' are used to represent the rest. (Case in the letters is +usually irrelevant; hexadecimal `a' and `A' have the same value.) +Thus, `11' in hexadecimal is 1 times 16 plus 1, which equals 17 in +decimal. Just by looking at plain `11', you can't tell what base it's in. So, in C, C++, and other languages derived from C, there is a special @@ -7376,13 +7376,13 @@ notation to signify the base. Octal numbers start with a leading `0', and hexadecimal numbers start with a leading `0x' or `0X': `11' - Decimal value 11. + Decimal value 11 `011' - Octal 11, decimal value 9. + Octal 11, decimal value 9 `0x11' - Hexadecimal 11, decimal value 17. + Hexadecimal 11, decimal value 17 This example shows the difference: @@ -7401,11 +7401,11 @@ really need to do this, use the `--non-decimal-data' command-line option; *note Nondecimal Data::.) If you have octal or hexadecimal data, you can use the `strtonum()' function (*note String Functions::) to convert the data into a number. Most of the time, you will want to -use octal or hexadecimal constants when working with the built-in bit -manipulation functions; see *note Bitwise Functions::, for more +use octal or hexadecimal constants when working with the built-in +bit-manipulation functions; see *note Bitwise Functions::, for more information. - Unlike some early C implementations, `8' and `9' are not valid in + Unlike in some early C implementations, `8' and `9' are not valid in octal constants. For example, `gawk' treats `018' as decimal 18: $ gawk 'BEGIN { print "021 is", 021 ; print 018 }' @@ -7432,12 +7432,12 @@ File: gawk.info, Node: Regexp Constants, Prev: Nondecimal-numbers, Up: Consta 6.1.1.3 Regular Expression Constants .................................... -A regexp constant is a regular expression description enclosed in +A "regexp constant" is a regular expression description enclosed in slashes, such as `/^beginning and end$/'. Most regexps used in `awk' programs are constant, but the `~' and `!~' matching operators can also match computed or dynamic regexps (which are typically just ordinary -strings or variables that contain a regexp, but could be a more complex -expression). +strings or variables that contain a regexp, but could be more complex +expressions). File: gawk.info, Node: Using Constant Regexps, Next: Variables, Prev: Constants, Up: Values @@ -7489,7 +7489,7 @@ and `patsplit()' functions (*note String Functions::). Modern implementations of `awk', including `gawk', allow the third argument of `split()' to be a regexp constant, but some older implementations do not. (d.c.) Because some built-in functions accept regexp constants -as arguments, it can be confusing when attempting to use regexp +as arguments, confusion can arise when attempting to use regexp constants as arguments to user-defined functions (*note User-defined::). For example: @@ -7512,10 +7512,11 @@ User-defined::). For example: In this example, the programmer wants to pass a regexp constant to the user-defined function `mysub()', which in turn passes it on to either `sub()' or `gsub()'. However, what really happens is that the -`pat' parameter is either one or zero, depending upon whether or not -`$0' matches `/hi/'. `gawk' issues a warning when it sees a regexp -constant used as a parameter to a user-defined function, because -passing a truth value in this way is probably not what was intended. +`pat' parameter is assigned a value of either one or zero, depending +upon whether or not `$0' matches `/hi/'. `gawk' issues a warning when +it sees a regexp constant used as a parameter to a user-defined +function, because passing a truth value in this way is probably not +what was intended. File: gawk.info, Node: Variables, Next: Conversion, Prev: Using Constant Regexps, Up: Values @@ -7523,7 +7524,7 @@ File: gawk.info, Node: Variables, Next: Conversion, Prev: Using Constant Rege 6.1.3 Variables --------------- -Variables are ways of storing values at one point in your program for +"Variables" are ways of storing values at one point in your program for use later in another part of your program. They can be manipulated entirely within the program text, and they can also be assigned values on the `awk' command line. @@ -7552,14 +7553,14 @@ variables. A variable name is a valid expression by itself; it represents the variable's current value. Variables are given new values with -"assignment operators", "increment operators", and "decrement -operators". *Note Assignment Ops::. In addition, the `sub()' and -`gsub()' functions can change a variable's value, and the `match()', -`split()', and `patsplit()' functions can change the contents of their -array parameters. *Note String Functions::. +"assignment operators", "increment operators", and "decrement operators" +(*note Assignment Ops::). In addition, the `sub()' and `gsub()' +functions can change a variable's value, and the `match()', `split()', +and `patsplit()' functions can change the contents of their array +parameters (*note String Functions::). A few variables have special built-in meanings, such as `FS' (the -field separator), and `NF' (the number of fields in the current input +field separator) and `NF' (the number of fields in the current input record). *Note Built-in Variables::, for a list of the predefined variables. These predefined variables can be used and assigned just like all other variables, but their values are also used or changed @@ -7756,7 +7757,7 @@ point, so the default behavior was restored to use a period as the decimal point character. You can use the `--use-lc-numeric' option (*note Options::) to force `gawk' to use the locale's decimal point character. (`gawk' also uses the locale's decimal point character when -in POSIX mode, either via `--posix', or the `POSIXLY_CORRECT' +in POSIX mode, either via `--posix' or the `POSIXLY_CORRECT' environment variable, as shown previously.) *note table-locale-affects:: describes the cases in which the @@ -7772,10 +7773,10 @@ Input Use period Use locale Table 6.1: Locale decimal point versus a period - Finally, modern day formal standards and IEEE standard floating-point -representation can have an unusual but important effect on the way -`gawk' converts some special string values to numbers. The details are -presented in *note POSIX Floating Point Problems::. + Finally, modern-day formal standards and the IEEE standard +floating-point representation can have an unusual but important effect +on the way `gawk' converts some special string values to numbers. The +details are presented in *note POSIX Floating Point Problems::. File: gawk.info, Node: All Operators, Next: Truth Values and Conditions, Prev: Values, Up: Expressions @@ -7783,7 +7784,7 @@ File: gawk.info, Node: All Operators, Next: Truth Values and Conditions, Prev 6.2 Operators: Doing Something with Values ========================================== -This minor node introduces the "operators" which make use of the values +This minor node introduces the "operators" that make use of the values provided by constants and variables. * Menu: @@ -7964,7 +7965,7 @@ you'll get. ---------- Footnotes ---------- - (1) It happens that BWK `awk', `gawk' and `mawk' all "get it right," + (1) It happens that BWK `awk', `gawk', and `mawk' all "get it right," but you should not rely on this. @@ -8081,7 +8082,7 @@ righthand expression. For example: The indices of `bar' are practically guaranteed to be different, because `rand()' returns different values each time it is called. (Arrays and the `rand()' function haven't been covered yet. *Note Arrays::, and -*note Numeric Functions::, for more information). This example +*note Numeric Functions::, for more information.) This example illustrates an important fact about assignment operators: the lefthand expression is only evaluated _once_. @@ -8099,14 +8100,14 @@ converted to a number. Operator Effect -------------------------------------------------------------------------- -LVALUE `+=' INCREMENT Add INCREMENT to the value of LVALUE -LVALUE `-=' DECREMENT Subtract DECREMENT from the value of LVALUE -LVALUE `*=' Multiply the value of LVALUE by COEFFICIENT +LVALUE `+=' INCREMENT Add INCREMENT to the value of LVALUE. +LVALUE `-=' DECREMENT Subtract DECREMENT from the value of LVALUE. +LVALUE `*=' Multiply the value of LVALUE by COEFFICIENT. COEFFICIENT -LVALUE `/=' DIVISOR Divide the value of LVALUE by DIVISOR -LVALUE `%=' MODULUS Set LVALUE to its remainder by MODULUS -LVALUE `^=' POWER -LVALUE `**=' POWER Raise LVALUE to the power POWER (c.e.) +LVALUE `/=' DIVISOR Divide the value of LVALUE by DIVISOR. +LVALUE `%=' MODULUS Set LVALUE to its remainder by MODULUS. +LVALUE `^=' POWER Raise LVALUE to the power POWER. +LVALUE `**=' POWER Raise LVALUE to the power POWER. (c.e.) Table 6.2: Arithmetic assignment operators @@ -8191,8 +8192,8 @@ is a summary of increment and decrement expressions: Operator Evaluation Order - Doctor, doctor! It hurts when I do this! - So don't do that! -- Groucho Marx + Doctor, it hurts when I do this! + Then don't do that! -- Groucho Marx What happens for something like the following? @@ -8207,7 +8208,7 @@ Or something even stranger? In other words, when do the various side effects prescribed by the postfix operators (`b++') take effect? When side effects happen is -"implementation defined". In other words, it is up to the particular +"implementation-defined". In other words, it is up to the particular version of `awk'. The result for the first example may be 12 or 13, and for the second, it may be 22 or 23. @@ -8222,7 +8223,7 @@ File: gawk.info, Node: Truth Values and Conditions, Next: Function Calls, Pre =============================== In certain contexts, expression values also serve as "truth values"; -(i.e., they determine what should happen next as the program runs). This +i.e., they determine what should happen next as the program runs. This minor node describes how `awk' defines "true" and "false" and how values are compared. @@ -8276,10 +8277,10 @@ File: gawk.info, Node: Typing and Comparison, Next: Boolean Ops, Prev: Truth The Guide is definitive. Reality is frequently inaccurate. -- Douglas Adams, `The Hitchhiker's Guide to the Galaxy' - Unlike other programming languages, `awk' variables do not have a -fixed type. Instead, they can be either a number or a string, depending -upon the value that is assigned to them. We look now at how variables -are typed, and how `awk' compares variables. + Unlike in other programming languages, in `awk' variables do not +have a fixed type. Instead, they can be either a number or a string, +depending upon the value that is assigned to them. We look now at how +variables are typed, and how `awk' compares variables. * Menu: @@ -8300,16 +8301,16 @@ of the variable is important because the types of two variables determine how they are compared. Variable typing follows these rules: * A numeric constant or the result of a numeric operation has the - NUMERIC attribute. + "numeric" attribute. * A string constant or the result of a string operation has the - STRING attribute. + "string" attribute. * Fields, `getline' input, `FILENAME', `ARGV' elements, `ENVIRON' elements, and the elements of an array created by `match()', `split()', and `patsplit()' that are numeric strings have the - STRNUM attribute. Otherwise, they have the STRING attribute. - Uninitialized variables also have the STRNUM attribute. + "strnum" attribute. Otherwise, they have the "string" attribute. + Uninitialized variables also have the "strnum" attribute. * Attributes propagate across assignments but are not changed by any use. @@ -8351,12 +8352,13 @@ constant, then a string comparison is performed. Otherwise, a numeric comparison is performed. This point bears additional emphasis: All user input is made of -characters, and so is first and foremost of STRING type; input strings -that look numeric are additionally given the STRNUM attribute. Thus, -the six-character input string ` +3.14' receives the STRNUM attribute. +characters, and so is first and foremost of string type; input strings +that look numeric are additionally given the strnum attribute. Thus, +the six-character input string ` +3.14' receives the strnum attribute. In contrast, the eight characters `" +3.14"' appearing in program text comprise a string constant. The following examples print `1' when the -comparison between the two different constants is true, `0' otherwise: +comparison between the two different constants is true, and `0' +otherwise: $ echo ' +3.14' | awk '{ print($0 == " +3.14") }' True -| 1 @@ -8455,7 +8457,7 @@ comparison is: -| false the result is `false' because both `$1' and `$2' are user input. They -are numeric strings--therefore both have the STRNUM attribute, +are numeric strings--therefore both have the strnum attribute, dictating a numeric comparison. The purpose of the comparison rules and the use of numeric strings is to attempt to produce the behavior that is "least surprising," while still "doing the right thing." @@ -8514,7 +8516,7 @@ is an example to illustrate the difference, in an `en_US.UTF-8' locale: ---------- Footnotes ---------- (1) Technically, string comparison is supposed to behave the same -way as if the strings are compared with the C `strcoll()' function. +way as if the strings were compared with the C `strcoll()' function. File: gawk.info, Node: Boolean Ops, Next: Conditional Exp, Prev: Typing and Comparison, Up: Truth Values and Conditions @@ -8577,7 +8579,7 @@ Boolean operators are: The `&&' and `||' operators are called "short-circuit" operators because of the way they work. Evaluation of the full expression is -"short-circuited" if the result can be determined part way through its +"short-circuited" if the result can be determined partway through its evaluation. Statements that end with `&&' or `||' can be continued simply by @@ -8630,15 +8632,15 @@ File: gawk.info, Node: Conditional Exp, Prev: Boolean Ops, Up: Truth Values a A "conditional expression" is a special kind of expression that has three operands. It allows you to use one expression's value to select -one of two other expressions. The conditional expression is the same -as in the C language, as shown here: +one of two other expressions. The conditional expression in `awk' is +the same as in the C language, as shown here: SELECTOR ? IF-TRUE-EXP : IF-FALSE-EXP There are three subexpressions. The first, SELECTOR, is always computed first. If it is "true" (not zero or not null), then -IF-TRUE-EXP is computed next and its value becomes the value of the -whole expression. Otherwise, IF-FALSE-EXP is computed next and its +IF-TRUE-EXP is computed next, and its value becomes the value of the +whole expression. Otherwise, IF-FALSE-EXP is computed next, and its value becomes the value of the whole expression. For example, the following expression produces the absolute value of `x': @@ -8672,7 +8674,7 @@ A "function" is a name for a particular calculation. This enables you to ask for it by name at any point in the program. For example, the function `sqrt()' computes the square root of a number. - A fixed set of functions are "built-in", which means they are + A fixed set of functions are "built in", which means they are available in every `awk' program. The `sqrt()' function is one of these. *Note Built-in::, for a list of built-in functions and their descriptions. In addition, you can define functions for use in your @@ -8807,7 +8809,7 @@ precedence: Increment, decrement. `^ **' - Exponentiation. These operators group right-to-left. + Exponentiation. These operators group right to left. `+ - !' Unary plus, minus, logical "not." @@ -8834,7 +8836,7 @@ String concatenation operand of another operator. As a result, it does not make sense to use a redirection operator near another operator of lower precedence without parentheses. Such combinations (e.g., `print - foo > a ? b : c'), result in syntax errors. The correct way to + foo > a ? b : c') result in syntax errors. The correct way to write this statement is `print foo > (a ? b : c)'. `~ !~' @@ -8844,16 +8846,16 @@ String concatenation Array membership. `&&' - Logical "and". + Logical "and." `||' - Logical "or". + Logical "or." `?:' - Conditional. This operator groups right-to-left. + Conditional. This operator groups right to left. `= += -= *= /= %= ^= **=' - Assignment. These operators group right-to-left. + Assignment. These operators group right to left. NOTE: The `|&', `**', and `**=' operators are not specified by POSIX. For maximum portability, do not use them. @@ -8921,24 +8923,24 @@ File: gawk.info, Node: Expressions Summary, Prev: Locales, Up: Expressions * `awk' provides the usual arithmetic operators (addition, subtraction, multiplication, division, modulus), and unary plus - and minus. It also provides comparison operators, boolean - operators, array membership testing, and regexp matching - operators. String concatenation is accomplished by placing two - expressions next to each other; there is no explicit operator. - The three-operand `?:' operator provides an "if-else" test within - expressions. + and minus. It also provides comparison operators, Boolean + operators, an array membership testing operator, and regexp + matching operators. String concatenation is accomplished by + placing two expressions next to each other; there is no explicit + operator. The three-operand `?:' operator provides an "if-else" + test within expressions. * Assignment operators provide convenient shorthands for common arithmetic operations. - * In `awk', a value is considered to be true if it is non-zero _or_ + * In `awk', a value is considered to be true if it is nonzero _or_ non-null. Otherwise, the value is false. * A variable's type is set upon each assignment and may change over its lifetime. The type determines how it behaves in comparisons (string or numeric). - * Function calls return a value which may be used as part of a larger + * Function calls return a value that may be used as part of a larger expression. Expressions used to pass parameter values are fully evaluated before the function is called. `awk' provides built-in and user-defined functions; this is described in *note Functions::. @@ -9112,7 +9114,7 @@ inside Boolean patterns. Likewise, the special patterns `BEGIN', `END', `BEGINFILE', and `ENDFILE', which never match any input record, are not expressions and cannot appear inside Boolean patterns. - The precedence of the different operators which can appear in + The precedence of the different operators that can appear in patterns is described in *note Precedence::. @@ -9132,8 +9134,8 @@ following: prints every record in `myfile' between `on'/`off' pairs, inclusive. A range pattern starts out by matching BEGPAT against every input -record. When a record matches BEGPAT, the range pattern is "turned on" -and the range pattern matches this record as well. As long as the +record. When a record matches BEGPAT, the range pattern is "turned +on", and the range pattern matches this record as well. As long as the range pattern stays turned on, it automatically matches every input record read. The range pattern also matches ENDPAT against every input record; when this succeeds, the range pattern is "turned off" again for @@ -9251,7 +9253,7 @@ for more information on using library functions. *Note Library Functions::, for a number of useful library functions. If an `awk' program has only `BEGIN' rules and no other rules, then -the program exits after the `BEGIN' rule is run.(1) However, if an +the program exits after the `BEGIN' rules are run.(1) However, if an `END' rule exists, then the input is read, even if there are no other rules in the program. This is necessary in case the `END' rule checks the `FNR' and `NR' variables. @@ -9277,7 +9279,7 @@ give `$0' a real value is to execute a `getline' command without a variable (*note Getline::). Another way is simply to assign a value to `$0'. - The second point is similar to the first but from the other + The second point is similar to the first, but from the other direction. Traditionally, due largely to implementation issues, `$0' and `NF' were _undefined_ inside an `END' rule. The POSIX standard specifies that `NF' is available in an `END' rule. It contains the @@ -9338,7 +9340,7 @@ tasks that would otherwise be difficult or impossible to perform: entirely. Otherwise, `gawk' exits with the usual fatal error. * If you have written extensions that modify the record handling (by - inserting an "input parser," *note Input Parsers::), you can invoke + inserting an "input parser"; *note Input Parsers::), you can invoke them at this point, before `gawk' has started processing the file. (This is a _very_ advanced feature, currently used only by the `gawkextlib' project (http://gawkextlib.sourceforge.net).) @@ -9348,16 +9350,15 @@ last record in an input file. For the last input file, it will be called before any `END' rules. The `ENDFILE' rule is executed even for empty input files. - Normally, when an error occurs when reading input in the normal input -processing loop, the error is fatal. However, if an `ENDFILE' rule is -present, the error becomes non-fatal, and instead `ERRNO' is set. This -makes it possible to catch and process I/O errors at the level of the -`awk' program. + Normally, when an error occurs when reading input in the normal +input-processing loop, the error is fatal. However, if an `ENDFILE' +rule is present, the error becomes non-fatal, and instead `ERRNO' is +set. This makes it possible to catch and process I/O errors at the +level of the `awk' program. The `next' statement (*note Next Statement::) is not allowed inside either a `BEGINFILE' or an `ENDFILE' rule. The `nextfile' statement is -allowed only inside a `BEGINFILE' rule, but not inside an `ENDFILE' -rule. +allowed only inside a `BEGINFILE' rule, not inside an `ENDFILE' rule. The `getline' statement (*note Getline::) is restricted inside both `BEGINFILE' and `ENDFILE': only redirected forms of `getline' are @@ -9402,11 +9403,11 @@ following program: END { print nmatches, "found" }' /path/to/data The `awk' program consists of two pieces of quoted text that are -concatenated together to form the program. The first part is double -quoted, which allows substitution of the `pattern' shell variable -inside the quotes. The second part is single quoted. +concatenated together to form the program. The first part is +double-quoted, which allows substitution of the `pattern' shell +variable inside the quotes. The second part is single-quoted. - Variable substitution via quoting works, but can be potentially + Variable substitution via quoting works, but can potentially be messy. It requires a good understanding of the shell's quoting rules (*note Quoting::), and it's often difficult to correctly match up the quotes when reading the program. @@ -9603,15 +9604,15 @@ The body of this loop is a compound statement enclosed in braces, containing two statements. The loop works in the following manner: first, the value of `i' is set to one. Then, the `while' statement tests whether `i' is less than or equal to three. This is true when -`i' equals one, so the `i'-th field is printed. Then the `i++' +`i' equals one, so the `i'th field is printed. Then the `i++' increments the value of `i' and the loop repeats. The loop terminates when `i' reaches four. A newline is not required between the condition and the body; however, using one makes the program clearer unless the body is a -compound statement or else is very simple. The newline after the -open-brace that begins the compound statement is not required either, -but the program is harder to read without it. +compound statement or else is very simple. The newline after the open +brace that begins the compound statement is not required either, but the +program is harder to read without it. File: gawk.info, Node: Do Statement, Next: For Statement, Prev: While Statement, Up: Statements @@ -9634,7 +9635,7 @@ Contrast this with the corresponding `while' statement: while (CONDITION) BODY -This statement does not execute BODY even once if the CONDITION is +This statement does not execute the BODY even once if the CONDITION is false to begin with. The following is an example of a `do' statement: { @@ -9690,7 +9691,7 @@ loop.) The same is true of the INCREMENT part. Incrementing additional variables requires separate statements at the end of the loop. The C compound expression, using C's comma operator, is useful in this -context but it is not supported in `awk'. +context, but it is not supported in `awk'. Most often, INCREMENT is an increment expression, as in the previous example. But this is not required; it can be any expression @@ -9766,7 +9767,7 @@ statement looks like this: Control flow in the `switch' statement works as it does in C. Once a match to a given case is made, the case statement bodies execute until -a `break', `continue', `next', `nextfile' or `exit' is encountered, or +a `break', `continue', `next', `nextfile', or `exit' is encountered, or the end of the `switch' statement itself. For example: while ((c = getopt(ARGC, ARGV, "aksx")) != -1) { @@ -10009,12 +10010,11 @@ listed in `ARGV'. standard. See the Austin Group website (http://austingroupbugs.net/view.php?id=607). - The current version of BWK `awk', and `mawk' also support -`nextfile'. However, they don't allow the `nextfile' statement inside -function bodies (*note User-defined::). `gawk' does; a `nextfile' -inside a function body reads the next record and starts processing it -with the first rule in the program, just as any other `nextfile' -statement. + The current version of BWK `awk' and `mawk' also support `nextfile'. +However, they don't allow the `nextfile' statement inside function +bodies (*note User-defined::). `gawk' does; a `nextfile' inside a +function body reads the next record and starts processing it with the +first rule in the program, just as any other `nextfile' statement. File: gawk.info, Node: Exit Statement, Prev: Nextfile Statement, Up: Statements @@ -10042,9 +10042,9 @@ record, skips reading any remaining input records, and executes the they do not execute. In such a case, if you don't want the `END' rule to do its job, set -a variable to nonzero before the `exit' statement and check that -variable in the `END' rule. *Note Assert Function::, for an example -that does this. +a variable to a nonzero value before the `exit' statement and check +that variable in the `END' rule. *Note Assert Function::, for an +example that does this. If an argument is supplied to `exit', its value is used as the exit status code for the `awk' process. If no argument is supplied, `exit' @@ -10102,7 +10102,7 @@ of activity. File: gawk.info, Node: User-modified, Next: Auto-set, Up: Built-in Variables -7.5.1 Built-In Variables That Control `awk' +7.5.1 Built-in Variables That Control `awk' ------------------------------------------- The following is an alphabetical list of variables that you can change @@ -33171,7 +33171,7 @@ Index * getline from a file: Getline/File. (line 6) * getline into a variable: Getline/Variable. (line 6) * getline statement, BEGINFILE/ENDFILE patterns and: BEGINFILE/ENDFILE. - (line 54) + (line 53) * getlocaltime() user-defined function: Getlocaltime Function. (line 16) * getopt() function (C library): Getopt Function. (line 15) @@ -34739,424 +34739,424 @@ Ref: Close Files And Pipes-Footnote-2315367 Node: Output Summary315517 Node: Output Exercises316515 Node: Expressions317195 -Node: Values318380 -Node: Constants319058 -Node: Scalar Constants319749 -Ref: Scalar Constants-Footnote-1320608 -Node: Nondecimal-numbers320858 -Node: Regexp Constants323876 -Node: Using Constant Regexps324401 -Node: Variables327544 -Node: Using Variables328199 -Node: Assignment Options330110 -Node: Conversion331985 -Node: Strings And Numbers332509 -Ref: Strings And Numbers-Footnote-1335574 -Node: Locale influences conversions335683 -Ref: table-locale-affects338430 -Node: All Operators339018 -Node: Arithmetic Ops339648 -Node: Concatenation342153 -Ref: Concatenation-Footnote-1344972 -Node: Assignment Ops345078 -Ref: table-assign-ops350057 -Node: Increment Ops351329 -Node: Truth Values and Conditions354767 -Node: Truth Values355852 -Node: Typing and Comparison356901 -Node: Variable Typing357711 -Node: Comparison Operators361364 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Symbol table by cookie970396 +Ref: Symbol table by cookie-Footnote-1974540 +Node: Cached values974603 +Ref: Cached values-Footnote-1978102 +Node: Array Manipulation978193 +Ref: Array Manipulation-Footnote-1979291 +Node: Array Data Types979328 +Ref: Array Data Types-Footnote-1981983 +Node: Array Functions982075 +Node: Flattening Arrays985929 +Node: Creating Arrays992821 +Node: Extension API Variables997592 +Node: Extension Versioning998228 +Node: Extension API Informational Variables1000129 +Node: Extension API Boilerplate1001194 +Node: Finding Extensions1005003 +Node: Extension Example1005563 +Node: Internal File Description1006335 +Node: Internal File Ops1010402 +Ref: Internal File Ops-Footnote-11022072 +Node: Using Internal File Ops1022212 +Ref: Using Internal File Ops-Footnote-11024595 +Node: Extension Samples1024868 +Node: Extension Sample File Functions1026394 +Node: Extension Sample Fnmatch1034032 +Node: Extension Sample Fork1035523 +Node: Extension Sample Inplace1036738 +Node: Extension Sample Ord1038413 +Node: Extension Sample Readdir1039249 +Ref: table-readdir-file-types1040125 +Node: Extension Sample Revout1040936 +Node: Extension Sample Rev2way1041526 +Node: Extension Sample Read write array1042266 +Node: Extension Sample Readfile1044206 +Node: Extension Sample Time1045301 +Node: Extension Sample API Tests1046650 +Node: gawkextlib1047141 +Node: Extension summary1049799 +Node: Extension Exercises1053488 +Node: Language History1054210 +Node: V7/SVR3.11055866 +Node: SVR41058047 +Node: POSIX1059492 +Node: BTL1060881 +Node: POSIX/GNU1061615 +Node: Feature History1067239 +Node: Common Extensions1080337 +Node: Ranges and Locales1081661 +Ref: Ranges and Locales-Footnote-11086279 +Ref: Ranges and Locales-Footnote-21086306 +Ref: Ranges and Locales-Footnote-31086540 +Node: Contributors1086761 +Node: History summary1092302 +Node: Installation1093672 +Node: Gawk Distribution1094618 +Node: Getting1095102 +Node: Extracting1095925 +Node: Distribution contents1097560 +Node: Unix Installation1103625 +Node: Quick Installation1104308 +Node: Shell Startup Files1106719 +Node: Additional Configuration Options1107798 +Node: Configuration Philosophy1109537 +Node: Non-Unix Installation1111906 +Node: PC Installation1112364 +Node: PC Binary Installation1113683 +Node: PC Compiling1115531 +Ref: PC Compiling-Footnote-11118552 +Node: PC Testing1118661 +Node: PC Using1119837 +Node: Cygwin1123952 +Node: MSYS1124775 +Node: VMS Installation1125275 +Node: VMS Compilation1126067 +Ref: VMS Compilation-Footnote-11127289 +Node: VMS Dynamic Extensions1127347 +Node: VMS Installation Details1129031 +Node: VMS Running1131283 +Node: VMS GNV1134119 +Node: VMS Old Gawk1134853 +Node: Bugs1135323 +Node: Other Versions1139206 +Node: Installation summary1145630 +Node: Notes1146686 +Node: Compatibility Mode1147551 +Node: Additions1148333 +Node: Accessing The Source1149258 +Node: Adding Code1150693 +Node: New Ports1156850 +Node: Derived Files1161332 +Ref: Derived Files-Footnote-11166807 +Ref: Derived Files-Footnote-21166841 +Ref: Derived Files-Footnote-31167437 +Node: Future Extensions1167551 +Node: Implementation Limitations1168157 +Node: Extension Design1169405 +Node: Old Extension Problems1170559 +Ref: Old Extension Problems-Footnote-11172076 +Node: Extension New Mechanism Goals1172133 +Ref: Extension New Mechanism Goals-Footnote-11175493 +Node: Extension Other Design Decisions1175682 +Node: Extension Future Growth1177790 +Node: Old Extension Mechanism1178626 +Node: Notes summary1180388 +Node: Basic Concepts1181574 +Node: Basic High Level1182255 +Ref: figure-general-flow1182527 +Ref: figure-process-flow1183126 +Ref: Basic High Level-Footnote-11186355 +Node: Basic Data Typing1186540 +Node: Glossary1189868 +Node: Copying1221797 +Node: GNU Free Documentation License1259353 +Node: Index1284489 End Tag Table diff --git a/doc/gawk.texi b/doc/gawk.texi index a0995368..ac973b9b 100644 --- a/doc/gawk.texi +++ b/doc/gawk.texi @@ -10510,7 +10510,7 @@ can assign a new value to a variable or a field by using an assignment operator. An expression can serve as a pattern or action statement on its own. Most other kinds of statements contain one or more expressions that specify the data on which to -operate. As in other languages, expressions in @command{awk} include +operate. As in other languages, expressions in @command{awk} can include variables, array references, constants, and function calls, as well as combinations of these with various operators. @@ -10529,7 +10529,7 @@ combinations of these with various operators. Expressions are built up from values and the operations performed upon them. This @value{SECTION} describes the elementary objects -which provide the values used in expressions. +that provide the values used in expressions. @menu * Constants:: String, numeric and regexp constants. @@ -10579,7 +10579,7 @@ have the same value: @end example @cindex string constants -A string constant consists of a sequence of characters enclosed in +A @dfn{string constant} consists of a sequence of characters enclosed in double quotation marks. For example: @example @@ -10591,7 +10591,7 @@ double quotation marks. For example: @cindex strings, length limitations represents the string whose contents are @samp{parrot}. Strings in @command{gawk} can be of any length, and they can contain any of the possible -eight-bit ASCII characters including ASCII @sc{nul} (character code zero). +eight-bit ASCII characters, including ASCII @sc{nul} (character code zero). Other @command{awk} implementations may have difficulty with some character codes. @@ -10606,15 +10606,15 @@ In @command{awk}, all numbers are in decimal (i.e., base 10). Many other programming languages allow you to specify numbers in other bases, often octal (base 8) and hexadecimal (base 16). In octal, the numbers go 0, 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, and so on. -Just as @samp{11}, in decimal, is 1 times 10 plus 1, so -@samp{11}, in octal, is 1 times 8, plus 1. This equals 9 in decimal. +Just as @samp{11} in decimal is 1 times 10 plus 1, so +@samp{11} in octal is 1 times 8 plus 1. This equals 9 in decimal. In hexadecimal, there are 16 digits. Because the everyday decimal number system only has ten digits (@samp{0}--@samp{9}), the letters @samp{a} through @samp{f} are used to represent the rest. (Case in the letters is usually irrelevant; hexadecimal @samp{a} and @samp{A} have the same value.) -Thus, @samp{11}, in -hexadecimal, is 1 times 16 plus 1, which equals 17 in decimal. +Thus, @samp{11} in +hexadecimal is 1 times 16 plus 1, which equals 17 in decimal. Just by looking at plain @samp{11}, you can't tell what base it's in. So, in C, C++, and other languages derived from C, @@ -10625,13 +10625,13 @@ and hexadecimal numbers start with a leading @samp{0x} or @samp{0X}: @table @code @item 11 -Decimal value 11. +Decimal value 11 @item 011 -Octal 11, decimal value 9. +Octal 11, decimal value 9 @item 0x11 -Hexadecimal 11, decimal value 17. +Hexadecimal 11, decimal value 17 @end table This example shows the difference: @@ -10659,11 +10659,11 @@ you can use the @code{strtonum()} function (@pxref{String Functions}) to convert the data into a number. Most of the time, you will want to use octal or hexadecimal constants -when working with the built-in bit manipulation functions; +when working with the built-in bit-manipulation functions; see @DBREF{Bitwise Functions} for more information. -Unlike some early C implementations, @samp{8} and @samp{9} are not +Unlike in some early C implementations, @samp{8} and @samp{9} are not valid in octal constants. For example, @command{gawk} treats @samp{018} as decimal 18: @@ -10732,12 +10732,12 @@ $ @kbd{gawk 'BEGIN @{ printf "0x11 is <%s>\n", 0x11 @}'} @cindex tilde (@code{~}), @code{~} operator @cindex @code{!} (exclamation point), @code{!~} operator @cindex exclamation point (@code{!}), @code{!~} operator -A regexp constant is a regular expression description enclosed in +A @dfn{regexp constant} is a regular expression description enclosed in slashes, such as @code{@w{/^beginning and end$/}}. Most regexps used in @command{awk} programs are constant, but the @samp{~} and @samp{!~} matching operators can also match computed or dynamic regexps (which are typically just ordinary strings or variables that contain a regexp, -but could be a more complex expression). +but could be more complex expressions). @node Using Constant Regexps @subsection Using Regular Expression Constants @@ -10817,7 +10817,7 @@ the third argument of @code{split()} to be a regexp constant, but some older implementations do not. @value{DARKCORNER} Because some built-in functions accept regexp constants as arguments, -it can be confusing when attempting to use regexp constants as arguments +confusion can arise when attempting to use regexp constants as arguments to user-defined functions (@pxref{User-defined}). For example: @example @@ -10843,7 +10843,7 @@ function mysub(pat, repl, str, global) In this example, the programmer wants to pass a regexp constant to the user-defined function @code{mysub()}, which in turn passes it on to either @code{sub()} or @code{gsub()}. However, what really happens is that -the @code{pat} parameter is either one or zero, depending upon whether +the @code{pat} parameter is assigned a value of either one or zero, depending upon whether or not @code{$0} matches @code{/hi/}. @command{gawk} issues a warning when it sees a regexp constant used as a parameter to a user-defined function, because passing a truth value in @@ -10854,7 +10854,7 @@ this way is probably not what was intended. @cindex variables, user-defined @cindex user-defined, variables -Variables are ways of storing values at one point in your program for +@dfn{Variables} are ways of storing values at one point in your program for use later in another part of your program. They can be manipulated entirely within the program text, and they can also be assigned values on the @command{awk} command line. @@ -10882,17 +10882,17 @@ are distinct variables. A variable name is a valid expression by itself; it represents the variable's current value. Variables are given new values with @dfn{assignment operators}, @dfn{increment operators}, and -@dfn{decrement operators}. -@xref{Assignment Ops}. +@dfn{decrement operators} +(@pxref{Assignment Ops}). In addition, the @code{sub()} and @code{gsub()} functions can change a variable's value, and the @code{match()}, @code{split()}, and @code{patsplit()} functions can change the contents of their -array parameters. @xref{String Functions}. +array parameters (@pxref{String Functions}). @cindex variables, built-in @cindex variables, initializing A few variables have special built-in meanings, such as @code{FS} (the -field separator), and @code{NF} (the number of fields in the current input +field separator) and @code{NF} (the number of fields in the current input record). @DBXREF{Built-in Variables} for a list of the predefined variables. These predefined variables can be used and assigned just like all other variables, but their values are also used or changed automatically by @@ -11149,7 +11149,7 @@ point, so the default behavior was restored to use a period as the decimal point character. You can use the @option{--use-lc-numeric} option (@pxref{Options}) to force @command{gawk} to use the locale's decimal point character. (@command{gawk} also uses the locale's decimal -point character when in POSIX mode, either via @option{--posix}, or the +point character when in POSIX mode, either via @option{--posix} or the @env{POSIXLY_CORRECT} environment variable, as shown previously.) @ref{table-locale-affects} describes the cases in which the locale's decimal @@ -11167,7 +11167,7 @@ features have not been described yet. @end multitable @end float -Finally, modern day formal standards and IEEE standard floating-point +Finally, modern-day formal standards and the IEEE standard floating-point representation can have an unusual but important effect on the way @command{gawk} converts some special string values to numbers. The details are presented in @ref{POSIX Floating Point Problems}. @@ -11175,7 +11175,7 @@ are presented in @ref{POSIX Floating Point Problems}. @node All Operators @section Operators: Doing Something with Values -This @value{SECTION} introduces the @dfn{operators} which make use +This @value{SECTION} introduces the @dfn{operators} that make use of the values provided by constants and variables. @menu @@ -11353,7 +11353,7 @@ print "something meaningful" > file name @noindent This produces a syntax error with some versions of Unix @command{awk}.@footnote{It happens that BWK -@command{awk}, @command{gawk} and @command{mawk} all ``get it right,'' +@command{awk}, @command{gawk}, and @command{mawk} all ``get it right,'' but you should not rely on this.} It is necessary to use the following: @@ -11603,7 +11603,7 @@ and @ifdocbook @DBREF{Numeric Functions} @end ifdocbook -for more information). +for more information.) This example illustrates an important fact about assignment operators: the lefthand expression is only evaluated @emph{once}. @@ -11639,17 +11639,17 @@ to a number. @caption{Arithmetic assignment operators} @multitable @columnfractions .30 .70 @headitem Operator @tab Effect -@item @var{lvalue} @code{+=} @var{increment} @tab Add @var{increment} to the value of @var{lvalue} -@item @var{lvalue} @code{-=} @var{decrement} @tab Subtract @var{decrement} from the value of @var{lvalue} -@item @var{lvalue} @code{*=} @var{coefficient} @tab Multiply the value of @var{lvalue} by @var{coefficient} -@item @var{lvalue} @code{/=} @var{divisor} @tab Divide the value of @var{lvalue} by @var{divisor} -@item @var{lvalue} @code{%=} @var{modulus} @tab Set @var{lvalue} to its remainder by @var{modulus} +@item @var{lvalue} @code{+=} @var{increment} @tab Add @var{increment} to the value of @var{lvalue}. +@item @var{lvalue} @code{-=} @var{decrement} @tab Subtract @var{decrement} from the value of @var{lvalue}. +@item @var{lvalue} @code{*=} @var{coefficient} @tab Multiply the value of @var{lvalue} by @var{coefficient}. +@item @var{lvalue} @code{/=} @var{divisor} @tab Divide the value of @var{lvalue} by @var{divisor}. +@item @var{lvalue} @code{%=} @var{modulus} @tab Set @var{lvalue} to its remainder by @var{modulus}. @cindex common extensions, @code{**=} operator @cindex extensions, common@comma{} @code{**=} operator @cindex @command{awk} language, POSIX version @cindex POSIX @command{awk} -@item @var{lvalue} @code{^=} @var{power} @tab -@item @var{lvalue} @code{**=} @var{power} @tab Raise @var{lvalue} to the power @var{power} @value{COMMONEXT} +@item @var{lvalue} @code{^=} @var{power} @tab Raise @var{lvalue} to the power @var{power}. +@item @var{lvalue} @code{**=} @var{power} @tab Raise @var{lvalue} to the power @var{power}. @value{COMMONEXT} @end multitable @end float @@ -11845,8 +11845,8 @@ like @samp{@var{lvalue}++}, but instead of adding, it subtracts.) @cindex evaluation order @cindex Marx, Groucho @quotation -@i{Doctor, doctor! It hurts when I do this!@* -So don't do that!} +@i{Doctor, it hurts when I do this!@* +Then don't do that!} @author Groucho Marx @end quotation @@ -11870,7 +11870,7 @@ print b @cindex side effects In other words, when do the various side effects prescribed by the postfix operators (@samp{b++}) take effect? -When side effects happen is @dfn{implementation defined}. +When side effects happen is @dfn{implementation-defined}. In other words, it is up to the particular version of @command{awk}. The result for the first example may be 12 or 13, and for the second, it may be 22 or 23. @@ -11897,8 +11897,8 @@ You should avoid such things in your own programs. @cindex evaluation order @cindex Marx, Groucho @quotation -@i{Doctor, doctor! It hurts when I do this!@* -So don't do that!} +@i{Doctor, it hurts when I do this!@* +Then don't do that!} @author Groucho Marx @end quotation @@ -11922,7 +11922,7 @@ print b @cindex side effects In other words, when do the various side effects prescribed by the postfix operators (@samp{b++}) take effect? -When side effects happen is @dfn{implementation defined}. +When side effects happen is @dfn{implementation-defined}. In other words, it is up to the particular version of @command{awk}. The result for the first example may be 12 or 13, and for the second, it may be 22 or 23. @@ -11938,8 +11938,8 @@ You should avoid such things in your own programs. @node Truth Values and Conditions @section Truth Values and Conditions -In certain contexts, expression values also serve as ``truth values''; (i.e., -they determine what should happen next as the program runs). This +In certain contexts, expression values also serve as ``truth values''; i.e., +they determine what should happen next as the program runs. This @value{SECTION} describes how @command{awk} defines ``true'' and ``false'' and how values are compared. @@ -12006,7 +12006,7 @@ the string constant @code{"0"} is actually true, because it is non-null. @cindex operators, relational, See operators@comma{} comparison @cindex variable typing @cindex variables, types of, comparison expressions and -Unlike other programming languages, @command{awk} variables do not have a +Unlike in other programming languages, in @command{awk} variables do not have a fixed type. Instead, they can be either a number or a string, depending upon the value that is assigned to them. We look now at how variables are typed, and how @command{awk} @@ -12035,20 +12035,20 @@ Variable typing follows these rules: @itemize @value{BULLET} @item -A numeric constant or the result of a numeric operation has the @var{numeric} +A numeric constant or the result of a numeric operation has the @dfn{numeric} attribute. @item -A string constant or the result of a string operation has the @var{string} +A string constant or the result of a string operation has the @dfn{string} attribute. @item Fields, @code{getline} input, @code{FILENAME}, @code{ARGV} elements, @code{ENVIRON} elements, and the elements of an array created by @code{match()}, @code{split()}, and @code{patsplit()} that are numeric -strings have the @var{strnum} attribute. Otherwise, they have -the @var{string} attribute. Uninitialized variables also have the -@var{strnum} attribute. +strings have the @dfn{strnum} attribute. Otherwise, they have +the @dfn{string} attribute. Uninitialized variables also have the +@dfn{strnum} attribute. @item Attributes propagate across assignments but are not changed by @@ -12192,13 +12192,13 @@ constant, then a string comparison is performed. Otherwise, a numeric comparison is performed. This point bears additional emphasis: All user input is made of characters, -and so is first and foremost of @var{string} type; input strings -that look numeric are additionally given the @var{strnum} attribute. +and so is first and foremost of string type; input strings +that look numeric are additionally given the strnum attribute. Thus, the six-character input string @w{@samp{ +3.14}} receives the -@var{strnum} attribute. In contrast, the eight characters +strnum attribute. In contrast, the eight characters @w{@code{" +3.14"}} appearing in program text comprise a string constant. The following examples print @samp{1} when the comparison between -the two different constants is true, @samp{0} otherwise: +the two different constants is true, and @samp{0} otherwise: @c 22.9.2014: Tested with mawk and BWK awk, got same results. @example @@ -12328,7 +12328,7 @@ $ @kbd{echo 1e2 3 | awk '@{ print ($1 < $2) ? "true" : "false" @}'} @noindent the result is @samp{false} because both @code{$1} and @code{$2} are user input. They are numeric strings---therefore both have -the @var{strnum} attribute, dictating a numeric comparison. +the strnum attribute, dictating a numeric comparison. The purpose of the comparison rules and the use of numeric strings is to attempt to produce the behavior that is ``least surprising,'' while still ``doing the right thing.'' @@ -12387,7 +12387,7 @@ characters sort, as defined by the locale (for more discussion, @pxref{Locales}). This order is usually very different from the results obtained when doing straight character-by-character comparison.@footnote{Technically, string comparison is supposed -to behave the same way as if the strings are compared with the C +to behave the same way as if the strings were compared with the C @code{strcoll()} function.} Because this behavior differs considerably from existing practice, @@ -12494,7 +12494,7 @@ BEGIN @{ if (! ("HOME" in ENVIRON)) @cindex vertical bar (@code{|}), @code{||} operator The @samp{&&} and @samp{||} operators are called @dfn{short-circuit} operators because of the way they work. Evaluation of the full expression -is ``short-circuited'' if the result can be determined part way through +is ``short-circuited'' if the result can be determined partway through its evaluation. @cindex line continuations @@ -12566,8 +12566,8 @@ The reason it's there is to avoid printing the bracketing A @dfn{conditional expression} is a special kind of expression that has three operands. It allows you to use one expression's value to select one of two other expressions. -The conditional expression is the same as in the C language, -as shown here: +The conditional expression in @command{awk} is the same as in the C +language, as shown here: @example @var{selector} ? @var{if-true-exp} : @var{if-false-exp} @@ -12576,8 +12576,8 @@ as shown here: @noindent There are three subexpressions. The first, @var{selector}, is always computed first. If it is ``true'' (not zero or not null), then -@var{if-true-exp} is computed next and its value becomes the value of -the whole expression. Otherwise, @var{if-false-exp} is computed next +@var{if-true-exp} is computed next, and its value becomes the value of +the whole expression. Otherwise, @var{if-false-exp} is computed next, and its value becomes the value of the whole expression. For example, the following expression produces the absolute value of @code{x}: @@ -12625,7 +12625,7 @@ ask for it by name at any point in the program. For example, the function @code{sqrt()} computes the square root of a number. @cindex functions, built-in -A fixed set of functions are @dfn{built-in}, which means they are +A fixed set of functions are @dfn{built in}, which means they are available in every @command{awk} program. The @code{sqrt()} function is one of these. @DBXREF{Built-in} for a list of built-in functions and their descriptions. In addition, you can define @@ -12799,7 +12799,7 @@ Increment, decrement. @cindex @code{*} (asterisk), @code{**} operator @cindex asterisk (@code{*}), @code{**} operator @item @code{^ **} -Exponentiation. These operators group right-to-left. +Exponentiation. These operators group right to left. @cindex @code{+} (plus sign), @code{+} operator @cindex plus sign (@code{+}), @code{+} operator @@ -12865,7 +12865,7 @@ statements belong to the statement level, not to expressions. The redirection does not produce an expression that could be the operand of another operator. As a result, it does not make sense to use a redirection operator near another operator of lower precedence without -parentheses. Such combinations (e.g., @samp{print foo > a ? b : c}), +parentheses. Such combinations (e.g., @samp{print foo > a ? b : c}) result in syntax errors. The correct way to write this statement is @samp{print foo > (a ? b : c)}. @@ -12883,17 +12883,17 @@ Array membership. @cindex @code{&} (ampersand), @code{&&} operator @cindex ampersand (@code{&}), @code{&&} operator @item @code{&&} -Logical ``and''. +Logical ``and.'' @cindex @code{|} (vertical bar), @code{||} operator @cindex vertical bar (@code{|}), @code{||} operator @item @code{||} -Logical ``or''. +Logical ``or.'' @cindex @code{?} (question mark), @code{?:} operator @cindex question mark (@code{?}), @code{?:} operator @item @code{?:} -Conditional. This operator groups right-to-left. +Conditional. This operator groups right to left. @cindex @code{+} (plus sign), @code{+=} operator @cindex plus sign (@code{+}), @code{+=} operator @@ -12910,7 +12910,7 @@ Conditional. This operator groups right-to-left. @cindex @code{^} (caret), @code{^=} operator @cindex caret (@code{^}), @code{^=} operator @item @code{= += -= *= /= %= ^= **=} -Assignment. These operators group right-to-left. +Assignment. These operators group right to left. @end table @cindex POSIX @command{awk}, @code{**} operator and @@ -12984,8 +12984,8 @@ Locales can influence the conversions. @item @command{awk} provides the usual arithmetic operators (addition, subtraction, multiplication, division, modulus), and unary plus and minus. -It also provides comparison operators, boolean operators, array membership -testing, and regexp +It also provides comparison operators, Boolean operators, an array membership +testing operator, and regexp matching operators. String concatenation is accomplished by placing two expressions next to each other; there is no explicit operator. The three-operand @samp{?:} operator provides an ``if-else'' test within @@ -12996,7 +12996,7 @@ Assignment operators provide convenient shorthands for common arithmetic operations. @item -In @command{awk}, a value is considered to be true if it is non-zero +In @command{awk}, a value is considered to be true if it is nonzero @emph{or} non-null. Otherwise, the value is false. @item @@ -13005,7 +13005,7 @@ lifetime. The type determines how it behaves in comparisons (string or numeric). @item -Function calls return a value which may be used as part of a larger +Function calls return a value that may be used as part of a larger expression. Expressions used to pass parameter values are fully evaluated before the function is called. @command{awk} provides built-in and user-defined functions; this is described in @@ -13032,7 +13032,7 @@ a pattern with an associated action. This @value{CHAPTER} describes how you build patterns and actions, what kinds of things you can do within actions, and @command{awk}'s predefined variables. -The pattern-action rules and the statements available for use +The pattern--action rules and the statements available for use within actions form the core of @command{awk} programming. In a sense, everything covered up to here has been the foundation @@ -13223,7 +13223,7 @@ patterns. Likewise, the special patterns @code{BEGIN}, @code{END}, which never match any input record, are not expressions and cannot appear inside Boolean patterns. -The precedence of the different operators which can appear in +The precedence of the different operators that can appear in patterns is described in @ref{Precedence}. @node Ranges @@ -13249,7 +13249,7 @@ prints every record in @file{myfile} between @samp{on}/@samp{off} pairs, inclusi A range pattern starts out by matching @var{begpat} against every input record. When a record matches @var{begpat}, the range pattern is -@dfn{turned on} and the range pattern matches this record as well. As long as +@dfn{turned on}, and the range pattern matches this record as well. As long as the range pattern stays turned on, it automatically matches every input record read. The range pattern also matches @var{endpat} against every input record; when this succeeds, the range pattern is @dfn{turned off} again @@ -13393,7 +13393,7 @@ using library functions. for a number of useful library functions. If an @command{awk} program has only @code{BEGIN} rules and no -other rules, then the program exits after the @code{BEGIN} rule is +other rules, then the program exits after the @code{BEGIN} rules are run.@footnote{The original version of @command{awk} kept reading and ignoring input until the end of the file was seen.} However, if an @code{END} rule exists, then the input is read, even if there are @@ -13421,7 +13421,7 @@ Another way is simply to assign a value to @code{$0}. @cindex @code{print} statement, @code{BEGIN}/@code{END} patterns and @cindex @code{BEGIN} pattern, @code{print} statement and @cindex @code{END} pattern, @code{print} statement and -The second point is similar to the first but from the other direction. +The second point is similar to the first, but from the other direction. Traditionally, due largely to implementation issues, @code{$0} and @code{NF} were @emph{undefined} inside an @code{END} rule. The POSIX standard specifies that @code{NF} is available in an @code{END} @@ -13510,7 +13510,7 @@ fatal error. @item If you have written extensions that modify the record handling (by -inserting an ``input parser,'' @pxref{Input Parsers}), you can invoke +inserting an ``input parser''; @pxref{Input Parsers}), you can invoke them at this point, before @command{gawk} has started processing the file. (This is a @emph{very} advanced feature, currently used only by the @uref{http://gawkextlib.sourceforge.net, @code{gawkextlib} project}.) @@ -13521,8 +13521,8 @@ the last record in an input file. For the last input file, it will be called before any @code{END} rules. The @code{ENDFILE} rule is executed even for empty input files. -Normally, when an error occurs when reading input in the normal input -processing loop, the error is fatal. However, if an @code{ENDFILE} +Normally, when an error occurs when reading input in the normal +input-processing loop, the error is fatal. However, if an @code{ENDFILE} rule is present, the error becomes non-fatal, and instead @code{ERRNO} is set. This makes it possible to catch and process I/O errors at the level of the @command{awk} program. @@ -13531,7 +13531,7 @@ level of the @command{awk} program. The @code{next} statement (@pxref{Next Statement}) is not allowed inside either a @code{BEGINFILE} or an @code{ENDFILE} rule. The @code{nextfile} statement is allowed only inside a -@code{BEGINFILE} rule, but not inside an @code{ENDFILE} rule. +@code{BEGINFILE} rule, not inside an @code{ENDFILE} rule. @cindex @code{getline} statement, @code{BEGINFILE}/@code{ENDFILE} patterns and The @code{getline} statement (@pxref{Getline}) is restricted inside @@ -13607,11 +13607,11 @@ awk "/$pattern/ "'@{ nmatches++ @} @noindent The @command{awk} program consists of two pieces of quoted text that are concatenated together to form the program. -The first part is double quoted, which allows substitution of +The first part is double-quoted, which allows substitution of the @code{pattern} shell variable inside the quotes. -The second part is single quoted. +The second part is single-quoted. -Variable substitution via quoting works, but can be potentially +Variable substitution via quoting works, but can potentially be messy. It requires a good understanding of the shell's quoting rules (@pxref{Quoting}), and it's often difficult to correctly @@ -13870,13 +13870,13 @@ The body of this loop is a compound statement enclosed in braces, containing two statements. The loop works in the following manner: first, the value of @code{i} is set to one. Then, the @code{while} statement tests whether @code{i} is less than or equal to -three. This is true when @code{i} equals one, so the @code{i}-th +three. This is true when @code{i} equals one, so the @code{i}th field is printed. Then the @samp{i++} increments the value of @code{i} and the loop repeats. The loop terminates when @code{i} reaches four. A newline is not required between the condition and the body; however, using one makes the program clearer unless the body is a -compound statement or else is very simple. The newline after the open-brace +compound statement or else is very simple. The newline after the open brace that begins the compound statement is not required either, but the program is harder to read without it. @@ -13906,9 +13906,9 @@ while (@var{condition}) @end example @noindent -This statement does not execute @var{body} even once if the @var{condition} -is false to begin with. -The following is an example of a @code{do} statement: +This statement does not execute the @var{body} even once if the +@var{condition} is false to begin with. The following is an example of +a @code{do} statement: @example @{ @@ -13975,7 +13975,7 @@ their assignments as separate statements preceding the @code{for} loop.) The same is true of the @var{increment} part. Incrementing additional variables requires separate statements at the end of the loop. The C compound expression, using C's comma operator, is useful in -this context but it is not supported in @command{awk}. +this context, but it is not supported in @command{awk}. Most often, @var{increment} is an increment expression, as in the previous example. But this is not required; it can be any expression @@ -14066,7 +14066,7 @@ default: Control flow in the @code{switch} statement works as it does in C. Once a match to a given case is made, the case statement bodies execute until a @code{break}, -@code{continue}, @code{next}, @code{nextfile} or @code{exit} is encountered, +@code{continue}, @code{next}, @code{nextfile}, or @code{exit} is encountered, or the end of the @code{switch} statement itself. For example: @example @@ -14240,7 +14240,12 @@ body of a loop. Historical versions of @command{awk} treated a @code{continue} statement outside a loop the same way they treated a @code{break} statement outside a loop: as if it were a @code{next} statement +@ifset FOR_PRINT +(discussed in the following section). +@end ifset +@ifclear FOR_PRINT (@pxref{Next Statement}). +@end ifclear @value{DARKCORNER} Recent versions of BWK @command{awk} no longer work this way, nor does @command{gawk}. @@ -14368,7 +14373,7 @@ See @uref{http://austingroupbugs.net/view.php?id=607, the Austin Group website}. @cindex @code{nextfile} statement, user-defined functions and @cindex Brian Kernighan's @command{awk} @cindex @command{mawk} utility -The current version of BWK @command{awk}, and @command{mawk} +The current version of BWK @command{awk} and @command{mawk} also support @code{nextfile}. However, they don't allow the @code{nextfile} statement inside function bodies (@pxref{User-defined}). @command{gawk} does; a @code{nextfile} inside a function body reads the @@ -14406,7 +14411,7 @@ any @code{ENDFILE} rules; they do not execute. In such a case, if you don't want the @code{END} rule to do its job, set a variable -to nonzero before the @code{exit} statement and check that variable in +to a nonzero value before the @code{exit} statement and check that variable in the @code{END} rule. @DBXREF{Assert Function} for an example that does this. @@ -14474,7 +14479,7 @@ their areas of activity. @end menu @node User-modified -@subsection Built-In Variables That Control @command{awk} +@subsection Built-in Variables That Control @command{awk} @cindex predefined variables, user-modifiable @cindex user-modifiable variables diff --git a/doc/gawktexi.in b/doc/gawktexi.in index dfa8cc03..9f20f608 100644 --- a/doc/gawktexi.in +++ b/doc/gawktexi.in @@ -10006,7 +10006,7 @@ can assign a new value to a variable or a field by using an assignment operator. An expression can serve as a pattern or action statement on its own. Most other kinds of statements contain one or more expressions that specify the data on which to -operate. As in other languages, expressions in @command{awk} include +operate. As in other languages, expressions in @command{awk} can include variables, array references, constants, and function calls, as well as combinations of these with various operators. @@ -10025,7 +10025,7 @@ combinations of these with various operators. Expressions are built up from values and the operations performed upon them. This @value{SECTION} describes the elementary objects -which provide the values used in expressions. +that provide the values used in expressions. @menu * Constants:: String, numeric and regexp constants. @@ -10075,7 +10075,7 @@ have the same value: @end example @cindex string constants -A string constant consists of a sequence of characters enclosed in +A @dfn{string constant} consists of a sequence of characters enclosed in double quotation marks. For example: @example @@ -10087,7 +10087,7 @@ double quotation marks. For example: @cindex strings, length limitations represents the string whose contents are @samp{parrot}. Strings in @command{gawk} can be of any length, and they can contain any of the possible -eight-bit ASCII characters including ASCII @sc{nul} (character code zero). +eight-bit ASCII characters, including ASCII @sc{nul} (character code zero). Other @command{awk} implementations may have difficulty with some character codes. @@ -10102,15 +10102,15 @@ In @command{awk}, all numbers are in decimal (i.e., base 10). Many other programming languages allow you to specify numbers in other bases, often octal (base 8) and hexadecimal (base 16). In octal, the numbers go 0, 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, and so on. -Just as @samp{11}, in decimal, is 1 times 10 plus 1, so -@samp{11}, in octal, is 1 times 8, plus 1. This equals 9 in decimal. +Just as @samp{11} in decimal is 1 times 10 plus 1, so +@samp{11} in octal is 1 times 8 plus 1. This equals 9 in decimal. In hexadecimal, there are 16 digits. Because the everyday decimal number system only has ten digits (@samp{0}--@samp{9}), the letters @samp{a} through @samp{f} are used to represent the rest. (Case in the letters is usually irrelevant; hexadecimal @samp{a} and @samp{A} have the same value.) -Thus, @samp{11}, in -hexadecimal, is 1 times 16 plus 1, which equals 17 in decimal. +Thus, @samp{11} in +hexadecimal is 1 times 16 plus 1, which equals 17 in decimal. Just by looking at plain @samp{11}, you can't tell what base it's in. So, in C, C++, and other languages derived from C, @@ -10121,13 +10121,13 @@ and hexadecimal numbers start with a leading @samp{0x} or @samp{0X}: @table @code @item 11 -Decimal value 11. +Decimal value 11 @item 011 -Octal 11, decimal value 9. +Octal 11, decimal value 9 @item 0x11 -Hexadecimal 11, decimal value 17. +Hexadecimal 11, decimal value 17 @end table This example shows the difference: @@ -10155,11 +10155,11 @@ you can use the @code{strtonum()} function (@pxref{String Functions}) to convert the data into a number. Most of the time, you will want to use octal or hexadecimal constants -when working with the built-in bit manipulation functions; +when working with the built-in bit-manipulation functions; see @DBREF{Bitwise Functions} for more information. -Unlike some early C implementations, @samp{8} and @samp{9} are not +Unlike in some early C implementations, @samp{8} and @samp{9} are not valid in octal constants. For example, @command{gawk} treats @samp{018} as decimal 18: @@ -10199,12 +10199,12 @@ $ @kbd{gawk 'BEGIN @{ printf "0x11 is <%s>\n", 0x11 @}'} @cindex tilde (@code{~}), @code{~} operator @cindex @code{!} (exclamation point), @code{!~} operator @cindex exclamation point (@code{!}), @code{!~} operator -A regexp constant is a regular expression description enclosed in +A @dfn{regexp constant} is a regular expression description enclosed in slashes, such as @code{@w{/^beginning and end$/}}. Most regexps used in @command{awk} programs are constant, but the @samp{~} and @samp{!~} matching operators can also match computed or dynamic regexps (which are typically just ordinary strings or variables that contain a regexp, -but could be a more complex expression). +but could be more complex expressions). @node Using Constant Regexps @subsection Using Regular Expression Constants @@ -10284,7 +10284,7 @@ the third argument of @code{split()} to be a regexp constant, but some older implementations do not. @value{DARKCORNER} Because some built-in functions accept regexp constants as arguments, -it can be confusing when attempting to use regexp constants as arguments +confusion can arise when attempting to use regexp constants as arguments to user-defined functions (@pxref{User-defined}). For example: @example @@ -10310,7 +10310,7 @@ function mysub(pat, repl, str, global) In this example, the programmer wants to pass a regexp constant to the user-defined function @code{mysub()}, which in turn passes it on to either @code{sub()} or @code{gsub()}. However, what really happens is that -the @code{pat} parameter is either one or zero, depending upon whether +the @code{pat} parameter is assigned a value of either one or zero, depending upon whether or not @code{$0} matches @code{/hi/}. @command{gawk} issues a warning when it sees a regexp constant used as a parameter to a user-defined function, because passing a truth value in @@ -10321,7 +10321,7 @@ this way is probably not what was intended. @cindex variables, user-defined @cindex user-defined, variables -Variables are ways of storing values at one point in your program for +@dfn{Variables} are ways of storing values at one point in your program for use later in another part of your program. They can be manipulated entirely within the program text, and they can also be assigned values on the @command{awk} command line. @@ -10349,17 +10349,17 @@ are distinct variables. A variable name is a valid expression by itself; it represents the variable's current value. Variables are given new values with @dfn{assignment operators}, @dfn{increment operators}, and -@dfn{decrement operators}. -@xref{Assignment Ops}. +@dfn{decrement operators} +(@pxref{Assignment Ops}). In addition, the @code{sub()} and @code{gsub()} functions can change a variable's value, and the @code{match()}, @code{split()}, and @code{patsplit()} functions can change the contents of their -array parameters. @xref{String Functions}. +array parameters (@pxref{String Functions}). @cindex variables, built-in @cindex variables, initializing A few variables have special built-in meanings, such as @code{FS} (the -field separator), and @code{NF} (the number of fields in the current input +field separator) and @code{NF} (the number of fields in the current input record). @DBXREF{Built-in Variables} for a list of the predefined variables. These predefined variables can be used and assigned just like all other variables, but their values are also used or changed automatically by @@ -10587,7 +10587,7 @@ point, so the default behavior was restored to use a period as the decimal point character. You can use the @option{--use-lc-numeric} option (@pxref{Options}) to force @command{gawk} to use the locale's decimal point character. (@command{gawk} also uses the locale's decimal -point character when in POSIX mode, either via @option{--posix}, or the +point character when in POSIX mode, either via @option{--posix} or the @env{POSIXLY_CORRECT} environment variable, as shown previously.) @ref{table-locale-affects} describes the cases in which the locale's decimal @@ -10605,7 +10605,7 @@ features have not been described yet. @end multitable @end float -Finally, modern day formal standards and IEEE standard floating-point +Finally, modern-day formal standards and the IEEE standard floating-point representation can have an unusual but important effect on the way @command{gawk} converts some special string values to numbers. The details are presented in @ref{POSIX Floating Point Problems}. @@ -10613,7 +10613,7 @@ are presented in @ref{POSIX Floating Point Problems}. @node All Operators @section Operators: Doing Something with Values -This @value{SECTION} introduces the @dfn{operators} which make use +This @value{SECTION} introduces the @dfn{operators} that make use of the values provided by constants and variables. @menu @@ -10791,7 +10791,7 @@ print "something meaningful" > file name @noindent This produces a syntax error with some versions of Unix @command{awk}.@footnote{It happens that BWK -@command{awk}, @command{gawk} and @command{mawk} all ``get it right,'' +@command{awk}, @command{gawk}, and @command{mawk} all ``get it right,'' but you should not rely on this.} It is necessary to use the following: @@ -11041,7 +11041,7 @@ and @ifdocbook @DBREF{Numeric Functions} @end ifdocbook -for more information). +for more information.) This example illustrates an important fact about assignment operators: the lefthand expression is only evaluated @emph{once}. @@ -11077,17 +11077,17 @@ to a number. @caption{Arithmetic assignment operators} @multitable @columnfractions .30 .70 @headitem Operator @tab Effect -@item @var{lvalue} @code{+=} @var{increment} @tab Add @var{increment} to the value of @var{lvalue} -@item @var{lvalue} @code{-=} @var{decrement} @tab Subtract @var{decrement} from the value of @var{lvalue} -@item @var{lvalue} @code{*=} @var{coefficient} @tab Multiply the value of @var{lvalue} by @var{coefficient} -@item @var{lvalue} @code{/=} @var{divisor} @tab Divide the value of @var{lvalue} by @var{divisor} -@item @var{lvalue} @code{%=} @var{modulus} @tab Set @var{lvalue} to its remainder by @var{modulus} +@item @var{lvalue} @code{+=} @var{increment} @tab Add @var{increment} to the value of @var{lvalue}. +@item @var{lvalue} @code{-=} @var{decrement} @tab Subtract @var{decrement} from the value of @var{lvalue}. +@item @var{lvalue} @code{*=} @var{coefficient} @tab Multiply the value of @var{lvalue} by @var{coefficient}. +@item @var{lvalue} @code{/=} @var{divisor} @tab Divide the value of @var{lvalue} by @var{divisor}. +@item @var{lvalue} @code{%=} @var{modulus} @tab Set @var{lvalue} to its remainder by @var{modulus}. @cindex common extensions, @code{**=} operator @cindex extensions, common@comma{} @code{**=} operator @cindex @command{awk} language, POSIX version @cindex POSIX @command{awk} -@item @var{lvalue} @code{^=} @var{power} @tab -@item @var{lvalue} @code{**=} @var{power} @tab Raise @var{lvalue} to the power @var{power} @value{COMMONEXT} +@item @var{lvalue} @code{^=} @var{power} @tab Raise @var{lvalue} to the power @var{power}. +@item @var{lvalue} @code{**=} @var{power} @tab Raise @var{lvalue} to the power @var{power}. @value{COMMONEXT} @end multitable @end float @@ -11226,8 +11226,8 @@ like @samp{@var{lvalue}++}, but instead of adding, it subtracts.) @cindex evaluation order @cindex Marx, Groucho @quotation -@i{Doctor, doctor! It hurts when I do this!@* -So don't do that!} +@i{Doctor, it hurts when I do this!@* +Then don't do that!} @author Groucho Marx @end quotation @@ -11251,7 +11251,7 @@ print b @cindex side effects In other words, when do the various side effects prescribed by the postfix operators (@samp{b++}) take effect? -When side effects happen is @dfn{implementation defined}. +When side effects happen is @dfn{implementation-defined}. In other words, it is up to the particular version of @command{awk}. The result for the first example may be 12 or 13, and for the second, it may be 22 or 23. @@ -11266,8 +11266,8 @@ You should avoid such things in your own programs. @node Truth Values and Conditions @section Truth Values and Conditions -In certain contexts, expression values also serve as ``truth values''; (i.e., -they determine what should happen next as the program runs). This +In certain contexts, expression values also serve as ``truth values''; i.e., +they determine what should happen next as the program runs. This @value{SECTION} describes how @command{awk} defines ``true'' and ``false'' and how values are compared. @@ -11334,7 +11334,7 @@ the string constant @code{"0"} is actually true, because it is non-null. @cindex operators, relational, See operators@comma{} comparison @cindex variable typing @cindex variables, types of, comparison expressions and -Unlike other programming languages, @command{awk} variables do not have a +Unlike in other programming languages, in @command{awk} variables do not have a fixed type. Instead, they can be either a number or a string, depending upon the value that is assigned to them. We look now at how variables are typed, and how @command{awk} @@ -11363,20 +11363,20 @@ Variable typing follows these rules: @itemize @value{BULLET} @item -A numeric constant or the result of a numeric operation has the @var{numeric} +A numeric constant or the result of a numeric operation has the @dfn{numeric} attribute. @item -A string constant or the result of a string operation has the @var{string} +A string constant or the result of a string operation has the @dfn{string} attribute. @item Fields, @code{getline} input, @code{FILENAME}, @code{ARGV} elements, @code{ENVIRON} elements, and the elements of an array created by @code{match()}, @code{split()}, and @code{patsplit()} that are numeric -strings have the @var{strnum} attribute. Otherwise, they have -the @var{string} attribute. Uninitialized variables also have the -@var{strnum} attribute. +strings have the @dfn{strnum} attribute. Otherwise, they have +the @dfn{string} attribute. Uninitialized variables also have the +@dfn{strnum} attribute. @item Attributes propagate across assignments but are not changed by @@ -11520,13 +11520,13 @@ constant, then a string comparison is performed. Otherwise, a numeric comparison is performed. This point bears additional emphasis: All user input is made of characters, -and so is first and foremost of @var{string} type; input strings -that look numeric are additionally given the @var{strnum} attribute. +and so is first and foremost of string type; input strings +that look numeric are additionally given the strnum attribute. Thus, the six-character input string @w{@samp{ +3.14}} receives the -@var{strnum} attribute. In contrast, the eight characters +strnum attribute. In contrast, the eight characters @w{@code{" +3.14"}} appearing in program text comprise a string constant. The following examples print @samp{1} when the comparison between -the two different constants is true, @samp{0} otherwise: +the two different constants is true, and @samp{0} otherwise: @c 22.9.2014: Tested with mawk and BWK awk, got same results. @example @@ -11656,7 +11656,7 @@ $ @kbd{echo 1e2 3 | awk '@{ print ($1 < $2) ? "true" : "false" @}'} @noindent the result is @samp{false} because both @code{$1} and @code{$2} are user input. They are numeric strings---therefore both have -the @var{strnum} attribute, dictating a numeric comparison. +the strnum attribute, dictating a numeric comparison. The purpose of the comparison rules and the use of numeric strings is to attempt to produce the behavior that is ``least surprising,'' while still ``doing the right thing.'' @@ -11715,7 +11715,7 @@ characters sort, as defined by the locale (for more discussion, @pxref{Locales}). This order is usually very different from the results obtained when doing straight character-by-character comparison.@footnote{Technically, string comparison is supposed -to behave the same way as if the strings are compared with the C +to behave the same way as if the strings were compared with the C @code{strcoll()} function.} Because this behavior differs considerably from existing practice, @@ -11822,7 +11822,7 @@ BEGIN @{ if (! ("HOME" in ENVIRON)) @cindex vertical bar (@code{|}), @code{||} operator The @samp{&&} and @samp{||} operators are called @dfn{short-circuit} operators because of the way they work. Evaluation of the full expression -is ``short-circuited'' if the result can be determined part way through +is ``short-circuited'' if the result can be determined partway through its evaluation. @cindex line continuations @@ -11894,8 +11894,8 @@ The reason it's there is to avoid printing the bracketing A @dfn{conditional expression} is a special kind of expression that has three operands. It allows you to use one expression's value to select one of two other expressions. -The conditional expression is the same as in the C language, -as shown here: +The conditional expression in @command{awk} is the same as in the C +language, as shown here: @example @var{selector} ? @var{if-true-exp} : @var{if-false-exp} @@ -11904,8 +11904,8 @@ as shown here: @noindent There are three subexpressions. The first, @var{selector}, is always computed first. If it is ``true'' (not zero or not null), then -@var{if-true-exp} is computed next and its value becomes the value of -the whole expression. Otherwise, @var{if-false-exp} is computed next +@var{if-true-exp} is computed next, and its value becomes the value of +the whole expression. Otherwise, @var{if-false-exp} is computed next, and its value becomes the value of the whole expression. For example, the following expression produces the absolute value of @code{x}: @@ -11953,7 +11953,7 @@ ask for it by name at any point in the program. For example, the function @code{sqrt()} computes the square root of a number. @cindex functions, built-in -A fixed set of functions are @dfn{built-in}, which means they are +A fixed set of functions are @dfn{built in}, which means they are available in every @command{awk} program. The @code{sqrt()} function is one of these. @DBXREF{Built-in} for a list of built-in functions and their descriptions. In addition, you can define @@ -12127,7 +12127,7 @@ Increment, decrement. @cindex @code{*} (asterisk), @code{**} operator @cindex asterisk (@code{*}), @code{**} operator @item @code{^ **} -Exponentiation. These operators group right-to-left. +Exponentiation. These operators group right to left. @cindex @code{+} (plus sign), @code{+} operator @cindex plus sign (@code{+}), @code{+} operator @@ -12193,7 +12193,7 @@ statements belong to the statement level, not to expressions. The redirection does not produce an expression that could be the operand of another operator. As a result, it does not make sense to use a redirection operator near another operator of lower precedence without -parentheses. Such combinations (e.g., @samp{print foo > a ? b : c}), +parentheses. Such combinations (e.g., @samp{print foo > a ? b : c}) result in syntax errors. The correct way to write this statement is @samp{print foo > (a ? b : c)}. @@ -12211,17 +12211,17 @@ Array membership. @cindex @code{&} (ampersand), @code{&&} operator @cindex ampersand (@code{&}), @code{&&} operator @item @code{&&} -Logical ``and''. +Logical ``and.'' @cindex @code{|} (vertical bar), @code{||} operator @cindex vertical bar (@code{|}), @code{||} operator @item @code{||} -Logical ``or''. +Logical ``or.'' @cindex @code{?} (question mark), @code{?:} operator @cindex question mark (@code{?}), @code{?:} operator @item @code{?:} -Conditional. This operator groups right-to-left. +Conditional. This operator groups right to left. @cindex @code{+} (plus sign), @code{+=} operator @cindex plus sign (@code{+}), @code{+=} operator @@ -12238,7 +12238,7 @@ Conditional. This operator groups right-to-left. @cindex @code{^} (caret), @code{^=} operator @cindex caret (@code{^}), @code{^=} operator @item @code{= += -= *= /= %= ^= **=} -Assignment. These operators group right-to-left. +Assignment. These operators group right to left. @end table @cindex POSIX @command{awk}, @code{**} operator and @@ -12312,8 +12312,8 @@ Locales can influence the conversions. @item @command{awk} provides the usual arithmetic operators (addition, subtraction, multiplication, division, modulus), and unary plus and minus. -It also provides comparison operators, boolean operators, array membership -testing, and regexp +It also provides comparison operators, Boolean operators, an array membership +testing operator, and regexp matching operators. String concatenation is accomplished by placing two expressions next to each other; there is no explicit operator. The three-operand @samp{?:} operator provides an ``if-else'' test within @@ -12324,7 +12324,7 @@ Assignment operators provide convenient shorthands for common arithmetic operations. @item -In @command{awk}, a value is considered to be true if it is non-zero +In @command{awk}, a value is considered to be true if it is nonzero @emph{or} non-null. Otherwise, the value is false. @item @@ -12333,7 +12333,7 @@ lifetime. The type determines how it behaves in comparisons (string or numeric). @item -Function calls return a value which may be used as part of a larger +Function calls return a value that may be used as part of a larger expression. Expressions used to pass parameter values are fully evaluated before the function is called. @command{awk} provides built-in and user-defined functions; this is described in @@ -12360,7 +12360,7 @@ a pattern with an associated action. This @value{CHAPTER} describes how you build patterns and actions, what kinds of things you can do within actions, and @command{awk}'s predefined variables. -The pattern-action rules and the statements available for use +The pattern--action rules and the statements available for use within actions form the core of @command{awk} programming. In a sense, everything covered up to here has been the foundation @@ -12551,7 +12551,7 @@ patterns. Likewise, the special patterns @code{BEGIN}, @code{END}, which never match any input record, are not expressions and cannot appear inside Boolean patterns. -The precedence of the different operators which can appear in +The precedence of the different operators that can appear in patterns is described in @ref{Precedence}. @node Ranges @@ -12577,7 +12577,7 @@ prints every record in @file{myfile} between @samp{on}/@samp{off} pairs, inclusi A range pattern starts out by matching @var{begpat} against every input record. When a record matches @var{begpat}, the range pattern is -@dfn{turned on} and the range pattern matches this record as well. As long as +@dfn{turned on}, and the range pattern matches this record as well. As long as the range pattern stays turned on, it automatically matches every input record read. The range pattern also matches @var{endpat} against every input record; when this succeeds, the range pattern is @dfn{turned off} again @@ -12721,7 +12721,7 @@ using library functions. for a number of useful library functions. If an @command{awk} program has only @code{BEGIN} rules and no -other rules, then the program exits after the @code{BEGIN} rule is +other rules, then the program exits after the @code{BEGIN} rules are run.@footnote{The original version of @command{awk} kept reading and ignoring input until the end of the file was seen.} However, if an @code{END} rule exists, then the input is read, even if there are @@ -12749,7 +12749,7 @@ Another way is simply to assign a value to @code{$0}. @cindex @code{print} statement, @code{BEGIN}/@code{END} patterns and @cindex @code{BEGIN} pattern, @code{print} statement and @cindex @code{END} pattern, @code{print} statement and -The second point is similar to the first but from the other direction. +The second point is similar to the first, but from the other direction. Traditionally, due largely to implementation issues, @code{$0} and @code{NF} were @emph{undefined} inside an @code{END} rule. The POSIX standard specifies that @code{NF} is available in an @code{END} @@ -12838,7 +12838,7 @@ fatal error. @item If you have written extensions that modify the record handling (by -inserting an ``input parser,'' @pxref{Input Parsers}), you can invoke +inserting an ``input parser''; @pxref{Input Parsers}), you can invoke them at this point, before @command{gawk} has started processing the file. (This is a @emph{very} advanced feature, currently used only by the @uref{http://gawkextlib.sourceforge.net, @code{gawkextlib} project}.) @@ -12849,8 +12849,8 @@ the last record in an input file. For the last input file, it will be called before any @code{END} rules. The @code{ENDFILE} rule is executed even for empty input files. -Normally, when an error occurs when reading input in the normal input -processing loop, the error is fatal. However, if an @code{ENDFILE} +Normally, when an error occurs when reading input in the normal +input-processing loop, the error is fatal. However, if an @code{ENDFILE} rule is present, the error becomes non-fatal, and instead @code{ERRNO} is set. This makes it possible to catch and process I/O errors at the level of the @command{awk} program. @@ -12859,7 +12859,7 @@ level of the @command{awk} program. The @code{next} statement (@pxref{Next Statement}) is not allowed inside either a @code{BEGINFILE} or an @code{ENDFILE} rule. The @code{nextfile} statement is allowed only inside a -@code{BEGINFILE} rule, but not inside an @code{ENDFILE} rule. +@code{BEGINFILE} rule, not inside an @code{ENDFILE} rule. @cindex @code{getline} statement, @code{BEGINFILE}/@code{ENDFILE} patterns and The @code{getline} statement (@pxref{Getline}) is restricted inside @@ -12935,11 +12935,11 @@ awk "/$pattern/ "'@{ nmatches++ @} @noindent The @command{awk} program consists of two pieces of quoted text that are concatenated together to form the program. -The first part is double quoted, which allows substitution of +The first part is double-quoted, which allows substitution of the @code{pattern} shell variable inside the quotes. -The second part is single quoted. +The second part is single-quoted. -Variable substitution via quoting works, but can be potentially +Variable substitution via quoting works, but can potentially be messy. It requires a good understanding of the shell's quoting rules (@pxref{Quoting}), and it's often difficult to correctly @@ -13198,13 +13198,13 @@ The body of this loop is a compound statement enclosed in braces, containing two statements. The loop works in the following manner: first, the value of @code{i} is set to one. Then, the @code{while} statement tests whether @code{i} is less than or equal to -three. This is true when @code{i} equals one, so the @code{i}-th +three. This is true when @code{i} equals one, so the @code{i}th field is printed. Then the @samp{i++} increments the value of @code{i} and the loop repeats. The loop terminates when @code{i} reaches four. A newline is not required between the condition and the body; however, using one makes the program clearer unless the body is a -compound statement or else is very simple. The newline after the open-brace +compound statement or else is very simple. The newline after the open brace that begins the compound statement is not required either, but the program is harder to read without it. @@ -13234,9 +13234,9 @@ while (@var{condition}) @end example @noindent -This statement does not execute @var{body} even once if the @var{condition} -is false to begin with. -The following is an example of a @code{do} statement: +This statement does not execute the @var{body} even once if the +@var{condition} is false to begin with. The following is an example of +a @code{do} statement: @example @{ @@ -13303,7 +13303,7 @@ their assignments as separate statements preceding the @code{for} loop.) The same is true of the @var{increment} part. Incrementing additional variables requires separate statements at the end of the loop. The C compound expression, using C's comma operator, is useful in -this context but it is not supported in @command{awk}. +this context, but it is not supported in @command{awk}. Most often, @var{increment} is an increment expression, as in the previous example. But this is not required; it can be any expression @@ -13394,7 +13394,7 @@ default: Control flow in the @code{switch} statement works as it does in C. Once a match to a given case is made, the case statement bodies execute until a @code{break}, -@code{continue}, @code{next}, @code{nextfile} or @code{exit} is encountered, +@code{continue}, @code{next}, @code{nextfile}, or @code{exit} is encountered, or the end of the @code{switch} statement itself. For example: @example @@ -13568,7 +13568,12 @@ body of a loop. Historical versions of @command{awk} treated a @code{continue} statement outside a loop the same way they treated a @code{break} statement outside a loop: as if it were a @code{next} statement +@ifset FOR_PRINT +(discussed in the following section). +@end ifset +@ifclear FOR_PRINT (@pxref{Next Statement}). +@end ifclear @value{DARKCORNER} Recent versions of BWK @command{awk} no longer work this way, nor does @command{gawk}. @@ -13696,7 +13701,7 @@ See @uref{http://austingroupbugs.net/view.php?id=607, the Austin Group website}. @cindex @code{nextfile} statement, user-defined functions and @cindex Brian Kernighan's @command{awk} @cindex @command{mawk} utility -The current version of BWK @command{awk}, and @command{mawk} +The current version of BWK @command{awk} and @command{mawk} also support @code{nextfile}. However, they don't allow the @code{nextfile} statement inside function bodies (@pxref{User-defined}). @command{gawk} does; a @code{nextfile} inside a function body reads the @@ -13734,7 +13739,7 @@ any @code{ENDFILE} rules; they do not execute. In such a case, if you don't want the @code{END} rule to do its job, set a variable -to nonzero before the @code{exit} statement and check that variable in +to a nonzero value before the @code{exit} statement and check that variable in the @code{END} rule. @DBXREF{Assert Function} for an example that does this. @@ -13802,7 +13807,7 @@ their areas of activity. @end menu @node User-modified -@subsection Built-In Variables That Control @command{awk} +@subsection Built-in Variables That Control @command{awk} @cindex predefined variables, user-modifiable @cindex user-modifiable variables |