add getopt

diff --git a/Makefile b/Makefile
index c2c1e70b4307fcaaf7b1ca538f337a579cd40111..7fe04f11b0847f51e61061bc70bca015b890e644 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,6 @@
 include config.mk
 
-TARGETS = realpath nproc
+TARGETS = getopt nproc realpath
 SRC = $(TARGETS:=.c)
 BIN = $(TARGETS:=-install)
 UNI = $(TARGETS:=-uninstall)

diff --git a/getopt.1 b/getopt.1
new file mode 100644 (file)
index 0000000..9429263
--- /dev/null
+++ b/getopt.1
@@ -0,0 +1,130 @@
+.\"
+.Dd May 2026
+.Dt GETOPT 1
+.Os
+.Sh NAME
+.Nm getopt
+.Nd parse command options
+.Sh SYNOPSIS
+.Nm args=\`getopt Ar optstring $*\`
+; errcode=$?; set \-\- $args
+.Sh DESCRIPTION
+The
+.Nm
+utility is used to break up options in command lines for easy parsing by
+shell procedures, and to check for legal options.
+.Ar Optstring
+is a string of recognized option letters (see
+.Xr getopt 3 ) ;
+if a letter is followed by a colon, the option
+is expected to have an argument which may or may not be
+separated from it by white space.
+The special option
+.Ql \-\-
+is used to delimit the end of the options.
+The
+.Nm
+utility will place
+.Ql \-\-
+in the arguments at the end of the options,
+or recognize it if used explicitly.
+The shell arguments
+(\fB$1 $2\fR ...) are reset so that each option is
+preceded by a
+.Ql \-
+and in its own shell argument;
+each option argument is also in its own shell argument.
+.Sh EXIT STATUS
+The
+.Nm
+utility prints an error message on the standard error output and exits with
+status > 0 when it encounters an option letter not included in
+.Ar optstring .
+.Sh EXAMPLES
+The following code fragment shows how one might process the arguments
+for a command that can take the options
+.Fl a
+and
+.Fl b ,
+and the option
+.Fl o ,
+which requires an argument.
+.Bd -literal -offset indent
+args=\`getopt abo: $*\`
+# you should not use \`getopt abo: "$@"\` since that would parse
+# the arguments differently from what the set command below does.
+if [ $? -ne 0 ]; then
+       echo 'Usage: ...'
+       exit 2
+fi
+set \-\- $args
+# You cannot use the set command with a backquoted getopt directly,
+# since the exit code from getopt would be shadowed by those of set,
+# which is zero by definition.
+while :; do
+       case "$1" in
+       \-a|\-b)
+               echo "flag $1 set"; sflags="${1#-}$sflags"
+               shift
+               ;;
+       \-o)
+               echo "oarg is '$2'"; oarg="$2"
+               shift; shift
+               ;;
+       \-\-)
+               shift; break
+               ;;
+       esac
+done
+echo "single-char flags: '$sflags'"
+echo "oarg is '$oarg'"
+.Ed
+.Pp
+This code will accept any of the following as equivalent:
+.Bd -literal -offset indent
+cmd \-aoarg file1 file2
+cmd \-a \-o arg file1 file2
+cmd \-oarg -a file1 file2
+cmd \-a \-oarg \-\- file1 file2
+.Ed
+.Sh SEE ALSO
+.Xr getopts 1 ,
+.Xr sh 1 ,
+.Xr getopt 3
+.Sh HISTORY
+Written by
+.An Henry Spencer ,
+working from a Bell Labs manual page.
+Behavior believed identical to the Bell version.
+.Sh BUGS
+Whatever
+.Xr getopt 3
+has.
+.Pp
+Arguments containing white space or embedded shell metacharacters
+generally will not survive intact; this looks easy to fix but
+is not.
+People trying to fix
+.Nm
+or the example in this manpage should check the history of this file
+in
+.Fx .
+.Pp
+The error message for an invalid option is identified as coming
+from
+.Nm
+rather than from the shell procedure containing the invocation
+of
+.Nm ;
+this again is hard to fix.
+.Pp
+The precise best way to use the
+.Nm set
+command to set the arguments without disrupting the value(s) of
+shell options varies from one shell version to another.
+.Pp
+Each shellscript has to carry complex code to parse arguments halfway
+correctly (like the example presented here).
+A better getopt-like tool
+would move much of the complexity into the tool and keep the client
+shell scripts simpler.

diff --git a/getopt.c b/getopt.c
new file mode 100644 (file)
index 0000000..c4835b8
--- /dev/null
+++ b/getopt.c
@@ -0,0 +1,45 @@
+/*
+ * This material, written by Henry Spencer, was released by him
+ * into the public domain and is thus not subject to any copyright.
+ */
+
+#define _XOPEN_SOURCE 700
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+int
+main(int argc, char *argv[])
+{
+       int c;
+       int status = 0;
+
+       if (argc < 2) {
+               fprintf(stderr, "%s: no arguments given\n", argv[0]);
+               exit(2);
+       }
+
+       optind = 2;     /* Past the program name and the option letters. */
+       while ((c = getopt(argc, argv, argv[1])) != -1) {
+               switch (c) {
+               case '?':
+                       status = 1;     /* getopt routine gave message */
+                       break;
+               default:
+                       if (optarg != NULL)
+                               printf(" -%c %s", c, optarg);
+                       else
+                               printf(" -%c", c);
+                       break;
+               }
+       }
+
+       printf(" --");
+       for (; optind < argc; optind++)
+               printf(" %s", argv[optind]);
+       printf("\n");
+
+       return status;
+}