getopt/getopt.1

   1 .\" $FreeBSD: src/usr.bin/getopt/getopt.1,v 1.15 2002/04/19 23:43:02 charnier Exp $
   2 .\"
   3 .Dd April 3, 1999
   4 .Dt GETOPT 1
   5 .Os
   6 .Sh NAME
   7 .Nm getopt
   8 .Nd parse command options
   9 .Sh SYNOPSIS
  10 .Nm args=\`getopt Ar optstring $*\`
  11 ; errcode=$?; set \-\- $args
  12 .Sh DESCRIPTION
  13 The
  14 .Nm
  15 utility is used to break up options in command lines for easy parsing by
  16 shell procedures, and to check for legal options.
  17 .Ar Optstring
  18 is a string of recognized option letters (see
  19 .Xr getopt 3 ) ;
  20 if a letter is followed by a colon, the option
  21 is expected to have an argument which may or may not be
  22 separated from it by white space.
  23 The special option
  24 .Ql \-\-
  25 is used to delimit the end of the options.
  26 The
  27 .Nm
  28 utility will place
  29 .Ql \-\-
  30 in the arguments at the end of the options,
  31 or recognize it if used explicitly.
  32 The shell arguments
  33 (\fB$1 $2\fR ...) are reset so that each option is
  34 preceded by a
  35 .Ql \-
  36 and in its own shell argument;
  37 each option argument is also in its own shell argument.
  38 .Sh EXAMPLES
  39 The following code fragment shows how one might process the arguments
  40 for a command that can take the options
  41 .Fl a
  42 and
  43 .Fl b ,
  44 and the option
  45 .Fl o ,
  46 which requires an argument.
  47 .Pp
  48 .Bd -literal -offset indent
  49 args=\`getopt abo: $*\`
  50 # you should not use \`getopt abo: "$@"\` since that would parse
  51 # the arguments differently from what the set command below does.
  52 if [ $? != 0 ]
  53 then
  54         echo 'Usage: ...'
  55         exit 2
  56 fi
  57 set \-\- $args
  58 # You cannot use the set command with a backquoted getopt directly,
  59 # since the exit code from getopt would be shadowed by those of set,
  60 # which is zero by definition.
  61 for i
  62 do
  63         case "$i"
  64         in
  65                 \-a|\-b)
  66                         echo flag $i set; sflags="${i#-}$sflags";
  67                         shift;;
  68                 \-o)
  69                         echo oarg is "'"$2"'"; oarg="$2"; shift;
  70                         shift;;
  71                 \-\-)
  72                         shift; break;;
  73         esac
  74 done
  75 echo single-char flags: "'"$sflags"'"
  76 echo oarg is "'"$oarg"'"
  77 .Ed
  78 .Pp
  79 This code will accept any of the following as equivalent:
  80 .Pp
  81 .Bd -literal -offset indent
  82 cmd \-aoarg file file
  83 cmd \-a \-o arg file file
  84 cmd \-oarg -a file file
  85 cmd \-a \-oarg \-\- file file
  86 .Pp
  87 .Ed
  88 .Sh SEE ALSO
  89 .Xr sh 1 ,
  90 .Xr getopt 3
  91 .Sh DIAGNOSTICS
  92 The
  93 .Nm
  94 utility prints an error message on the standard error output and exits with
  95 status > 0 when it encounters an option letter not included in
  96 .Ar optstring .
  97 .Sh HISTORY
  98 Written by
  99 .An Henry Spencer ,
 100 working from a Bell Labs manual page.
 101 Behavior believed identical to the Bell version.
 102 Example changed in
 103 .Fx
 104 version 3.2 and 4.0.
 105 .Sh BUGS
 106 Whatever
 107 .Xr getopt 3
 108 has.
 109 .Pp
 110 Arguments containing white space or embedded shell metacharacters
 111 generally will not survive intact;  this looks easy to fix but
 112 isn't. People trying to fix
 113 .Nm
 114 or the example in this manpage should check the history of this file
 115 in
 116 .Fx .
 117 .Pp
 118 The error message for an invalid option is identified as coming
 119 from
 120 .Nm
 121 rather than from the shell procedure containing the invocation
 122 of
 123 .Nm ;
 124 this again is hard to fix.
 125 .Pp
 126 The precise best way to use the
 127 .Nm set
 128 command to set the arguments without disrupting the value(s) of
 129 shell options varies from one shell version to another.
 130 .Pp
 131 Each shellscript has to carry complex code to parse arguments halfway
 132 correcty (like the example presented here). A better getopt-like tool
 133 would move much of the complexity into the tool and keep the client
 134 shell scripts simpler.