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Diffstat (limited to 'doc/gawktexi.in')
| -rw-r--r-- | doc/gawktexi.in | 55 |
1 files changed, 25 insertions, 30 deletions
diff --git a/doc/gawktexi.in b/doc/gawktexi.in index 2269077e..56f119a8 100644 --- a/doc/gawktexi.in +++ b/doc/gawktexi.in @@ -1783,6 +1783,7 @@ see @uref{http://www.gnu.org, the GNU Project's home page}. This @value{DOCUMENT} may also be read from @uref{http://www.gnu.org/software/gawk/manual/, their web site}. +@ifclear FOR_PRINT A shell, an editor (Emacs), highly portable optimizing C, C++, and Objective-C compilers, a symbolic debugger and dozens of large and small utilities (such as @command{gawk}), have all been completed and are @@ -1793,32 +1794,16 @@ stage of development. @cindex Linux @cindex GNU/Linux @cindex operating systems, BSD-based -@cindex Alpha (DEC) Until the GNU operating system is more fully developed, you should consider using GNU/Linux, a freely distributable, Unix-like operating system for Intel@registeredsymbol{}, Power Architecture, Sun SPARC, IBM S/390, and other -@ifclear FOR_PRINT systems.@footnote{The terminology ``GNU/Linux'' is explained in the @ref{Glossary}.} -@end ifclear -@ifset FOR_PRINT -systems. -@end ifset Many GNU/Linux distributions are available for download from the Internet. - -(There are numerous other freely available, Unix-like operating systems -based on the -Berkeley Software Distribution, and some of them use recent versions -of @command{gawk} for their versions of @command{awk}. -@uref{http://www.netbsd.org, NetBSD}, -@uref{http://www.freebsd.org, FreeBSD}, -and -@uref{http://www.openbsd.org, OpenBSD} -are three of the most popular ones, but there -are others.) +@end ifclear @ifnotinfo The @value{DOCUMENT} you are reading is actually free---at least, the @@ -2062,10 +2047,14 @@ people. Notable code and documentation contributions were made by a number of people. @xref{Contributors}, for the full list. -Thanks to Patrice Dumas for the new @command{makeinfo} program. +Thanks to Patrice Dumas for the new @command{makeinfo} program. Thanks to Karl Berry who continues to work to keep the Texinfo markup language sane. +Robert P.J.@: Day, Michael Brennan and Brian Kernighan kindly acted as +reviewers for the 2015 edition of this @value{DOCUMENT}. Their feedback +helped improve the final work. + @cindex Kernighan, Brian I would like to thank Brian Kernighan for invaluable assistance during the testing and debugging of @command{gawk}, and for ongoing @@ -2073,6 +2062,12 @@ help and advice in clarifying numerous points about the language. We could not have done nearly as good a job on either @command{gawk} or its documentation without his help. +Brian is in a class by himself as a programmer and technical +author. I have to thank him (yet again) for his ongoing friendship +and the role-model he has been for me for close to 30 years! +Having him as a reviewer is an exciting privilege. It has also +been extremely humbling@enddots{} + @cindex Robbins, Miriam @cindex Robbins, Jean @cindex Robbins, Harry @@ -2946,12 +2941,14 @@ action---so it uses the default action, printing the record. Print the length of the longest line in @file{data}: @example -expand data | awk '@{ if (x < length()) x = length() @} +expand data | awk '@{ if (x < length($0)) x = length($0) @} END @{ print "maximum line length is " x @}' @end example +This example differs slightly from the first example in this list: The input is processed by the @command{expand} utility to change TABs -into spaces, so the widths compared are actually the right-margin columns. +into spaces, so the widths compared are actually the right-margin columns, +as opposed to the number of input characters on each line. @item Print every line that has at least one field: @@ -9326,7 +9323,8 @@ print "Serious error detected!" | "cat 1>&2" @noindent This works by opening a pipeline to a shell command that can access the standard error stream that it inherits from the @command{awk} process. -This is far from elegant, and it is also inefficient, because it requires a +@c 8/2014: Mike Brennan says not to cite this as inefficient. So, fixed. +This is far from elegant, and it also requires a separate process. So people writing @command{awk} programs often don't do this. Instead, they send the error messages to the screen, like this: @@ -10626,7 +10624,7 @@ Otherwise, it's parsed as follows: @end display As mentioned earlier, -when doing concatenation, @emph{parenthesize}. Otherwise, +when mixing concatenation with other operators, @emph{parenthesize}. Otherwise, you're never quite sure what you'll get. @node Assignment Ops @@ -11112,19 +11110,14 @@ compares variables. @cindex numeric, strings @cindex strings, numeric @cindex POSIX @command{awk}, numeric strings and -The 1992 POSIX standard introduced +The POSIX standard introduced the concept of a @dfn{numeric string}, which is simply a string that looks like a number---for example, @code{@w{" +2"}}. This concept is used for determining the type of a variable. The type of the variable is important because the types of two variables determine how they are compared. +Variable typing follows these rules: -The various versions of the POSIX standard did not get the rules -quite right for several editions. Fortunately, as of at least the -2008 standard (and possibly earlier), the standard has been fixed, -and variable typing follows these rules:@footnote{@command{gawk} has -followed these rules for many years, -and it is gratifying that the POSIX standard is also now correct.} @itemize @value{BULLET} @item @@ -15950,7 +15943,9 @@ is @minus{}3, and @code{int(-3)} is @minus{}3 as well. @cindexawkfunc{log} @cindex logarithm Return the natural logarithm of @var{x}, if @var{x} is positive; -otherwise, report an error. +otherwise, return @code{NaN} (``not a number'') on IEEE 754 systems. +Additionally, @command{gawk} prints a warning message when @code{x} +is negative. @item @code{rand()} @cindexawkfunc{rand} |