getopt.3

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· 3 代码 · 共 136 行

.\" SCCSID: @(#)getopt.3	8.1	9/11/90
.TH getopt 3
.SH Name
getopt \- get option letter from argument vector
.SH Syntax
.B #include <stdio.h>
.br
.B int getopt (argc, argv, optstring)
.br
.B int argc;
.br
.B char \(**\(**argv;
.br
.B char \(**optstring;
.PP
.B extern char \(**optarg;
.br
.B extern int optind, opterr;
.br
.SH Description
.NXR "getopt subroutine"
.NXR "argument vector" "getting option letter"
The
.PN getopt
subroutine
returns the next option letter in
.I argv\^
that matches
a letter in
.IR optstring .
The
.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.
The
.I optarg\^
is set to point to the start of the option argument
on return from
.PN getopt .
.PP
The function
.PN getopt\^
places in
.I optind\^
the
.I argv\^
index of the next argument to be processed.
The external variable optind is automatically initialized to 1 before
the first call to 
.PN getopt .
.PP
When all options have been processed
(that is, up to the first non-option argument),
.PN getopt
returns EOF.
The special option
.B \-\-
may be used to delimit the end of the options; EOF
will be returned, and
.B \-\-
will be skipped.
.SH Diagnostics
The function
.PN getopt\^
prints an error message on
.I stderr\^
and returns a
question mark
.RB ( ? )
when it encounters an option letter that is not included in
.IR optstring .
Setting opterr to 0 disables this error message.
.SH Examples
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:
.EX 0
#include <stdio.h>
main (argc, argv)
int argc;
char \(**\(**argv;
{
       int c;
       extern int optind, opterr;
       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;
                        bufsiza = 512;
                        break;
                case '?':
                        errflg++;
                }
        if (errflg) {
                fprintf (stderr, "usage: . . . ");
                exit (2);
        }
        for ( ; optind < argc; optind++) {
               if (access (argv[optind], 4)) {
        .
        .
        .
}
.EE
.SH See Also
getopt(1)