getopt(3) Library Functions Manual getopt(3)Name
getopt - get option letter from argument vector
Syntax
#include <stdio.h>
int getopt (argc, argv, optstring)
int argc;
char **argv;
char *optstring;
extern char *optarg;
extern int optind, opterr;
Description
The subroutine returns the next option letter in argv that matches a letter in optstring. The 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 optarg is set to point to the start of the option argument on return from
The function places in optind the argv index of the next argument to be processed. The external variable optind is automatically initial-
ized to 1 before the first call to
When all options have been processed (that is, up to the first non-option argument), returns EOF. The special option -- may be used to
delimit the end of the options; EOF will be returned, and -- will be skipped.
Diagnostics
The function prints an error message on stderr and returns a question mark (?) when it encounters an option letter that is not included in
optstring. Setting opterr to 0 disables this error message.
Examples
The following code fragment shows how one might process the arguments for a command that can take the mutually exclusive options a and b,
and the options f and o, both of which require arguments:
#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)) {
.
.
.
}
See Alsogetopt(1)getopt(3)
Check Out this Related Man Page
getopt(3C)getopt(3C)NAME
getopt(), optarg, opterr, optind, optopt - get option letter from argument vector
SYNOPSIS DESCRIPTION
returns the next option letter in argv (starting from that matches a letter in optstring. argc and argv are the argument count and argu-
ment array as passed to optstring is a string of recognized option characters; if a character is followed by a colon, the option takes an
argument which may or may not be separated from it by whitespace.
is the index of the next element of the vector to be processed. It is initialized to 1 by the system, and updates it when it finishes with
each element of
returns the next option character from argv that matches a character in optstring, if there is one that matches. If the option takes an
argument, sets the variable to point to the option argument as follows:
o If the option was the last character in the string pointed to by an element of argv, then contains the next element of argv, and is
incremented by 2. If the resulting value of is greater than or equal to argc, this indicates a missing option argument, and returns
an error indication.
o Otherwise, points to the string following the option character in that element of argv, and is incremented by 1.
If, when is called, is NULL, or the string pointed to by either does not begin with the character or consists only of the character returns
-1 without changing If points to the string returns -1 after incrementing
If encounters an option character that is not contained in optstring, it returns the question-mark character. If it detects a missing
option argument, it returns the colon character if the first character of optstring was a colon, or a question-mark character otherwise.
In either case, sets the variable to the option character that caused the error. If the application has not set the variable to zero and
the first character of optstring is not a colon, also prints a diagnostic message to standard error.
The special option can be used to delimit the end of the options; -1 is returned, and is skipped.
RETURN VALUE
returns the next option character specified on the command line. A colon is returned if detects a missing argument and the first character
of optstring was a colon
A question-mark is returned if encounters an option character not in optstring or detects a missing argument and the first character of
optstring was not a colon
Otherwise, returns -1 when all command line options have been parsed.
EXTERNAL INFLUENCES
Locale
The category determines the interpretation of option letters as single and/or multi-byte characters.
International Code Set Support
Single- and multibyte character code sets are supported.
ERRORS
fails under the following conditions:
[EILSEQ] An invalid multibyte character sequence was encountered during option processing.
EXAMPLES
The following code fragment shows to process arguments for a command that can take the mutually exclusive options and and the options and
both of which require arguments:
#include <stdio.h>
#include <unistd.h>
main (int argc, char *argv[])
{
int c;
int bflg, aflg, errflg;
extern char *optarg;
extern int optind, optopt;
.
.
.
while ((c = getopt(argc, argv, ":abf:o:")) != -1)
switch (c) {
case 'a':
if (bflg)
errflg++;
else
aflg++;
break;
case 'b':
if (aflg)
errflg++;
else {
bflg++;
bproc( );
}
break;
case 'f':
ifile = optarg;
break;
case 'o':
ofile = optarg;
break;
case ':': /* -f or -o without arguments */
fprintf(stderr, "Option -%c requires an argument
",
optopt);
errflg++;
break;
case '?':
fprintf(stderr, "Unrecognized option: - %c
",
optopt);
errflg++;
}
if (errflg) {
fprintf(stderr, "usage: . . . ");
exit(2);
}
for ( ; optind < argc; optind++) {
if (access(argv[optind], 4)) {
.
.
.
}
WARNINGS
Options can be any ASCII characters except colon question mark or null
SEE ALSO getopt(1), thread_safety(5).
STANDARDS CONFORMANCE getopt(3C)