Message-ID: <anews.Autzoo.1269>
Newsgroups: net.sources
Path: utzoo!henry
X-Path: utzoo!henry
From: utzoo!henry
Date: Mon Jan 11 15:42:39 1982
Subject: getopt(3)
The following is the source and manual page for a getopt() routine
written locally to match the description in a copy of the Unix 3.0
manual that I got to see once. Behavior is believed identical to the
Bell one, but this is NOT Bell code and carries no nondisclosure
restrictions. Use it on any system you wish.
------------
/*
* getopt - get option letter from argv
*/
#include <stdio.h>
char *optarg; /* Global argument pointer. */
int optind = 0; /* Global argv index. */
static char *scan = NULL; /* Private scan pointer. */
extern char *index();
int
getopt(argc, argv, optstring)
int argc;
char *argv[];
char *optstring;
{
register char c;
register char *place;
optarg = NULL;
if (scan == NULL || *scan == '\0') {
if (optind == 0)
optind++;
if (optind >= argc || argv[optind][0] != '-' || argv[optind][1] == '\0')
return(EOF);
if (strcmp(argv[optind], "--")==0) {
optind++;
return(EOF);
}
scan = argv[optind]+1;
optind++;
}
c = *scan++;
place = index(optstring, c);
if (place == NULL || c == ':') {
fprintf(stderr, "%s: unknown option -%c\n", argv[0], c);
return('?');
}
place++;
if (*place == ':') {
if (*scan != '\0') {
optarg = scan;
scan = NULL;
} else {
optarg = argv[optind];
optind++;
}
}
return(c);
}
------------
.TH GETOPT 3 local
.DA 28 Oct 1981
.SH NAME
getopt \- get option letter from argv
.SH SYNOPSIS
.ft B
int getopt(argc, argv, optstring)
.br
int argc;
.br
char **argv;
.br
char *optstring;
.sp
extern char *optarg;
.br
extern int optind;
.ft
.SH DESCRIPTION
.I Getopt
returns the next option letter in
.I argv
that matches a letter in
.IR optstring .
.I Optstring
is a string of recognized option letters;
if a letter is followed by a colon, the option is expected to have
an argument that may or may not be separated from it by white space.
.I Optarg
is set to point to the start of the option argument on return from
.IR getopt .
.PP
.I Getopt
places in
.I optind
the
.I argv
index of the next argument to be processed.
Because
.I optind
is external, it is normally initialized to zero automatically
before the first call to
.IR getopt .
.PP
When all options have been processed (i.e., up to the first
non-option argument),
.I getopt
returns
.BR EOF .
The special option
.B \-\-
may be used to delimit the end of the options;
.B EOF
will be returned, and
.B \-\-
will be skipped.
.SH SEE ALSO
getopt(1)
.SH DIAGNOSTICS
.I Getopt
prints an error message on
.I stderr
and returns a question mark
.RB ( ? )
when it encounters an option letter not included in
.IR optstring .
.SH EXAMPLE
The following code fragment shows how one might process the arguments
for a command that can take the mutually exclusive options
.B a
and
.BR b ,
and the options
.B f
and
.BR o ,
both of which require arguments:
.PP
.RS
.nf
main(argc, argv)
int argc;
char **argv;
{
int c;
extern int optind;
extern char *optarg;
\&.
\&.
\&.
while ((c = getopt(argc, argv, "abf:o:")) != EOF)
switch (c) {
case 'a':
if (bflg)
errflg++;
else
aflg++;
break;
case 'b':
if (aflg)
errflg++;
else
bproc();
break;
case 'f':
ifile = optarg;
break;
case 'o':
ofile = optarg;
break;
case '?':
errflg++;
}
if (errflg) {
fprintf(stderr, "Usage: ...");
exit(2);
}
for (; optind < argc; optind++) {
\&.
\&.
\&.
}
\&.
\&.
\&.
}
.RE
.SH HISTORY
Written by Henry Spencer, working from a Bell Labs manual page.
Behavior believed identical to the Bell version.
.SH BUGS
It is not obvious how
`\-'
standing alone should be treated; this version treats it as
a non-option argument, which is not always right.
.PP
Option arguments are allowed to begin with `\-';
this is reasonable but reduces the amount of error checking possible.
.PP
.I Getopt
is quite flexible but the obvious price must be paid: there is much
it could do that it doesn't, like
checking mutually exclusive options, checking type of
option arguments, etc.
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