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Diffstat (limited to 'doc/gawktexi.in')
| -rw-r--r-- | doc/gawktexi.in | 114 |
1 files changed, 58 insertions, 56 deletions
diff --git a/doc/gawktexi.in b/doc/gawktexi.in index 2d13f518..6a9dfe0e 100644 --- a/doc/gawktexi.in +++ b/doc/gawktexi.in @@ -25008,8 +25008,6 @@ END @{ @node Uniq Program @subsection Printing Nonduplicated Lines of Text -@c FIXME: One day, update to current POSIX version of uniq - @cindex printing @subentry unduplicated lines of text @cindex text, printing @subentry unduplicated lines of @cindex @command{uniq} utility @@ -25019,7 +25017,7 @@ prints unique lines---hence the name. @command{uniq} has a number of options. The usage is as follows: @display -@command{uniq} [@option{-udc} [@code{-@var{n}}]] [@code{+@var{n}}] [@var{inputfile} [@var{outputfile}]] +@command{uniq} [@option{-udc} [@code{-f @var{n}}] [@code{-s @var{n}}]] [@var{inputfile} [@var{outputfile}]] @end display The options for @command{uniq} are: @@ -25035,14 +25033,14 @@ Print only nonrepeated (unique) lines. Count lines. This option overrides @option{-d} and @option{-u}. Both repeated and nonrepeated lines are counted. -@item -@var{n} +@item -f @var{n} Skip @var{n} fields before comparing lines. The definition of fields is similar to @command{awk}'s default: nonwhitespace characters separated by runs of spaces and/or TABs. -@item +@var{n} +@item -s @var{n} Skip @var{n} characters before comparing lines. Any fields specified with -@samp{-@var{n}} are skipped first. +@option{-f} are skipped first. @item @var{inputfile} Data is read from the input file named on the command line, instead of from @@ -25063,22 +25061,7 @@ and the @code{join()} library function (@pxref{Join Function}). The program begins with a @code{usage()} function and then a brief outline of -the options and their meanings in comments. -The @code{BEGIN} rule deals with the command-line arguments and options. It -uses a trick to get @code{getopt()} to handle options of the form @samp{-25}, -treating such an option as the option letter @samp{2} with an argument of -@samp{5}. If indeed two or more digits are supplied (@code{Optarg} looks -like a number), @code{Optarg} is -concatenated with the option digit and then the result is added to zero to make -it into a number. If there is only one digit in the option, then -@code{Optarg} is not needed. In this case, @code{Optind} must be decremented so that -@code{getopt()} processes it next time. This code is admittedly a bit -tricky. - -If no options are supplied, then the default is taken, to print both -repeated and nonrepeated lines. The output file, if provided, is assigned -to @code{outputfile}. Early on, @code{outputfile} is initialized to the -standard output, @file{/dev/stdout}: +the options and their meanings in comments: @cindex @code{uniq.awk} program @example @@ -25094,26 +25077,62 @@ standard output, @file{/dev/stdout}: # # Arnold Robbins, arnold@@skeeve.com, Public Domain # May 1993 +# Updated August 2020 to current POSIX @c endfile @end ignore @c file eg/prog/uniq.awk function usage() @{ - print("Usage: uniq [-udc [-n]] [+n] [ in [ out ]]") > "/dev/stderr" + print("Usage: uniq [-udc [-f fields] [-s chars]] [ in [ out ]]") > "/dev/stderr" exit 1 @} # -c count lines. overrides -d and -u # -d only repeated lines # -u only nonrepeated lines -# -n skip n fields -# +n skip n characters, skip fields first +# -f n skip n fields +# -s n skip n characters, skip fields first +@c endfile +@end example + +The POSIX standard for @command{uniq} allows options to start with +@samp{+} as well as with @samp{-}. An initial @code{BEGIN} rule +traverses the arguments changing any leading @samp{+} to @samp{-} +so that the @code{getopt()} function can parse the options: + +@example +@c file eg/prog/uniq.awk +# As of 2020, '+' can be used as option character in addition to '-' +# Previously allowed use of -N to skip fields and +N to skip +# characters is no longer allowed, and not supported by this version. + +BEGIN @{ + # Convert + to - so getopt can handle things + for (i = 1; i < ARGC; i++) @{ + first = substr(ARGV[i], 1, 1) + if (ARGV[i] == "--" || (first != "-" && first != "+")) + break + else if (first == "+") + # Replace "+" with "-" + ARGV[i] = "-" substr(ARGV[i], 2) + @} +@} +@c endfile +@end example + +The next @code{BEGIN} rule deals with the command-line arguments and options. +If no options are supplied, then the default is taken, to print both +repeated and nonrepeated lines. The output file, if provided, is assigned +to @code{outputfile}. Early on, @code{outputfile} is initialized to the +standard output, @file{/dev/stdout}: +@example +@c file eg/prog/uniq.awk BEGIN @{ count = 1 outputfile = "/dev/stdout" - opts = "udc0:1:2:3:4:5:6:7:8:9:" + opts = "udcf:s:" while ((c = getopt(ARGC, ARGV, opts)) != -1) @{ if (c == "u") non_repeated_only++ @@ -25121,26 +25140,14 @@ BEGIN @{ repeated_only++ else if (c == "c") do_count++ - else if (index("0123456789", c) != 0) @{ - # getopt() requires args to options - # this messes us up for things like -5 - if (Optarg ~ /^[[:digit:]]+$/) - fcount = (c Optarg) + 0 - else @{ - fcount = c + 0 - Optind-- - @} - @} else + else if (c == "f") + fcount = Optarg + 0 + else if (c == "s") + charcount = Optarg + 0 + else usage() @} -@group - if (ARGV[Optind] ~ /^\+[[:digit:]]+$/) @{ - charcount = substr(ARGV[Optind], 2) + 0 - Optind++ - @} -@end group - for (i = 1; i < Optind; i++) ARGV[i] = "" @@ -25270,20 +25277,15 @@ As a side note, this program does not follow our recommended convention of namin global variables with a leading capital letter. Doing that would make the program a little easier to follow. -@ifset FOR_PRINT The logic for choosing which lines to print represents a @dfn{state -machine}, which is ``a device that can be in one of a set number of stable -conditions depending on its previous condition and on the present values -of its inputs.''@footnote{This is the definition returned from entering -@code{define: state machine} into Google.} -Brian Kernighan suggests that -``an alternative approach to state machines is to just read -the input into an array, then use indexing. It's almost always -easier code, and for most inputs where you would use this, just -as fast.'' Consider how to rewrite the logic to follow this -suggestion. -@end ifset - +machine}, which is ``a device which can be in one of a set number +of stable conditions depending on its previous condition and on the +present values of its inputs.''@footnote{This definition is from +@uref{https://www.lexico.com/en/definition/state_machine}.} Brian +Kernighan suggests that ``an alternative approach to state machines is +to just read the input into an array, then use indexing. It's almost +always easier code, and for most inputs where you would use this, just +as fast.'' Consider how to rewrite the logic to follow this suggestion. @node Wc Program |