getopt(3)getopt(3)NAMEgetopt - Get option letters from the argument vector
SYNOPSIS
#include <unistd.h>
int getopt(
int argc,
char * const argv [],
const char *optstring );
extern char *optarg; extern int optind; extern int opterr; extern int
optopt;
LIBRARY
Standard C Library (libc)
STANDARDS
Interfaces documented on this reference page conform to industry stan‐
dards as follows:
getopt(): XSH5.0
Refer to the standards(5) reference page for more information about
industry standards and associated tags.
PARAMETERS
Specifies the number of parameters passed to the routine. Points to an
array of argc pointers to argument strings. Specifies a string of rec‐
ognized option characters. If a character is followed by a : (colon),
the option is expected to take a parameter that may or may not be sepa‐
rated from it by white space.
DESCRIPTION
The getopt() function parses argument lists. It returns the next option
character in the argv parameter list that matches a character in the
optstring parameter. If that option takes an argument, the getopt()
function has the optarg variable point to the option argument according
to the following rules: If the option is the last character pointed to
by an argv element, optarg will contain argv's next element, and optind
is incremented by 2. The getopt() function returns an error if the
resulting optind is greater than or equal to argc. If the option is
not the last character, then the optarg variable points to the string
after the option character in the associated element of argv. The
optind variable is incremented by 1.
The optarg external variable is set to point to the start of the
option's parameter on return from the getopt() function.
The getopt() function places the argv index of the next argument to be
processed in optind. The optind variable is externally initialized to 1
before the first call to getopt() so that argv[0] is not processed.
Error messages can be suppressed by providing a value of 0 (zero) as
the opterr parameter.
NOTES
[Tru64 UNIX] The external int optopt variable is set to the real
option found in the argv parameter. This is true whether the option is
in the optstring parameter or not.
RETURN VALUES
Upon successful completion, the getopt() function returns the option
character that was detected. If the function encounters a option that
is not included in the optstring parameter, or if the : (colon) charac‐
ter is used incorrectly, the getopt() function prints an error message
on stderr and returns a ? (question mark). If there is a missing
option, the getopt() function returns a : (colon) if optstring's first
character is a : (colon), and a ? (question mark) otherwise. In addi‐
tion, the getopt() function sets the optopt variable to the option
character that caused one of these errors.
The getopt() function also displays a diagnostic message if the appli‐
cation did not set the opterr variable to 0 (zero), and optstring's
first character is not a : (colon).
When all options have been processed (that is, up to the first nonop‐
tion argument), the getopt() function returns a value of -1. The spe‐
cial option -- (dash dash) can be used to delimit the end of the
options; -1 is returned, and the -- (dash dash) string is skipped.
The getopt() function does not change optind, and also returns a value
of -1, if one of the following occurs: The argv[optind] result is NULL.
The *argv[optind] result is not the special - (dash) option. The
argv[optind] result points to the - (dash) string.
The getopt() function does increment optind if the result of
argv[optind] points to the -- (dash dash) string.
EXAMPLES
The following example shows a suggested way to use the getopt() func‐
tion.
#include <unistd.h> main(argc, argv) int argc; char *argv[];
#define ARGS "r:w:f:s"
{
int c, errflg = 0;
int readers = 1, writers = 1;
int freeBufs = 1;
int doStats = FALSE;
optarg = NULL;
while (!errflg && ((c = getopt(argc, argv, ARGS)) != -1))
switch (c) {
case 'r' :
readers = atoi(optarg);
break;
case 'w' :
writers = atoi(optarg);
break;
case 'f' :
freeBufs = atoi(optarg);
break;
case 's' :
doStats = TRUE;
break;
default :
errflg++;
}
SEE ALSO
Commands: getopt(1)
Standards: standards(5)getopt(3)
