getopt.3c (2010 09)

g
getopt(3C) getopt(3C)
NAME
getopt(), optarg, opterr, optind, optopt - get option letter from argument vector
SYNOPSIS
#include <unistd.h>
int getopt(
int argc,
char * const argv[],
const char *optstring
);
extern char *optarg;
extern int optind, opterr, optopt;
DESCRIPTION
getopt() returns the next option letter in argv (starting from argv
[1]) that matches a letter in opt-
string . argc and argv are the argument count and argument array as passed to
main(). 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.
optind is the index of the next element of the argv [] vector to be processed. It is initialized to 1 by the
system, and getopt() updates it when it finishes with each element of argv [].
getopt() 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, getopt() sets the variable optarg to point to the
option argument as follows:
• If the option was the last character in the string pointed to by an element of argv , then
optarg
contains the next element of argv , and optind is incremented by 2. If the resulting value of
optind is greater than or equal to argc , this indicates a missing option argument, and getopt()
returns an error indication.
• Otherwise,
optarg points to the string following the option character in that element of argv , and
optind is incremented by 1.
If, when
getopt() is called, argv [optind] is NULL, or the string pointed to by argv
[optind]
either does not begin with the character - or consists only of the character -, getopt()
returns −1
without changing
optind.Ifargv[optind] points to the string --, getopt() returns −1 after
incrementing
optind.
If
getopt() 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,
getopt()
sets the variable optopt to the option character that caused the error. If the application has not set the
variable opterr to zero and the first character of optstring is not a colon, getopt() 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
getopt() returns the next option character specified on the command line. A colon (:) is returned if
getopt() detects a missing argument and the first character of optstring was a colon (:).
A question-mark (
?) is returned if getopt() encounters an option character not in optstring or detects
a missing argument and the first character of optstring was not a colon (:).
Otherwise,
getopt() returns −1 when all command line options have been parsed.
EXTERNAL INFLUENCES
Locale
The
LC_CTYPE category determines the interpretation of option letters as single and/or multi-byte char-
acters.
International Code Set Support
Single- and multibyte character code sets are supported.
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1