{"id":5110,"date":"2022-12-20T18:37:07","date_gmt":"2022-12-20T21:37:07","guid":{"rendered":"http:\/\/lode.uno\/linux-man\/index.php\/2022\/12\/20\/getopt-man3p\/"},"modified":"2022-12-20T18:37:07","modified_gmt":"2022-12-20T21:37:07","slug":"getopt-man3p","status":"publish","type":"post","link":"https:\/\/lode.uno\/linux-man\/2022\/12\/20\/getopt-man3p\/","title":{"rendered":"GETOPT (man3p)"},"content":{"rendered":"

GETOPT<\/h1>\n

PROLOG<\/a>
NAME<\/a>
SYNOPSIS<\/a>
DESCRIPTION<\/a>
RETURN VALUE<\/a>
ERRORS<\/a>
EXAMPLES<\/a>
APPLICATION USAGE<\/a>
RATIONALE<\/a>
FUTURE DIRECTIONS<\/a>
SEE ALSO<\/a>
COPYRIGHT<\/a> <\/p>\n

\n

PROLOG <\/a> <\/h2>\n

This manual page is part of the POSIX Programmer\u2019s Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.<\/p>\n

NAME <\/a> <\/h2>\n

getopt, optarg, opterr, optind, optopt \u2014 command option parsing<\/p>\n

SYNOPSIS <\/a> <\/h2>\n

#include <\/p>\n

int getopt(int argc<\/i>, char bodies manpages.csv script_extrae_body.sh script.sh usr const argv<\/i>[], const char *optstring<\/i>);
extern char *optarg;
extern int opterr, optind, optopt;<\/p>\n

DESCRIPTION <\/a> <\/h2>\n

The getopt<\/i>() function is a command-line parser that shall follow Utility Syntax Guidelines 3, 4, 5, 6, 7, 9, and 10 in the Base Definitions volume of POSIX.1-2017, Section 12.2<\/i>, Utility Syntax Guidelines<\/i>.<\/p>\n

The parameters argc<\/i> and argv<\/i> are the argument count and argument array as passed to main<\/i>() (see exec<\/i>()). The argument optstring<\/i> is a string of recognized option characters; if a character is followed by a , the option takes an argument. All option characters allowed by Utility Syntax Guideline 3 are allowed in optstring<\/i>. The implementation may accept other characters as an extension.<\/p>\n

The variable optind<\/i> is the index of the next element of the argv<\/i>[] vector to be processed. It shall be initialized to 1 by the system, and getopt<\/i>() shall update it when it finishes with each element of argv<\/i>[]. If the application sets optind<\/i> to zero before calling getopt<\/i>(), the behavior is unspecified. When an element of argv<\/i>[] contains multiple option characters, it is unspecified how getopt<\/i>() determines which options have already been processed.<\/p>\n

The getopt<\/i>() function shall return the next option character (if one is found) from argv<\/i> that matches a character in optstring<\/i>, if there is one that matches. If the option takes an argument, getopt<\/i>() shall set the variable optarg<\/i> to point to the option-argument as follows:<\/p>\n\n\n\n
<\/td>\n\n

1.<\/p>\n<\/td>\n

<\/td>\n\n

If the option was the last character in the string pointed to by an element of argv<\/i>, then optarg<\/i> shall contain the next element of argv<\/i>, and optind<\/i> shall be incremented by 2. If the resulting value of optind<\/i> is greater than argc<\/i>, this indicates a missing option-argument, and getopt<\/i>() shall return an error indication.<\/p>\n<\/td>\n<\/tr>\n

<\/td>\n\n

2.<\/p>\n<\/td>\n

<\/td>\n\n

Otherwise, optarg<\/i> shall point to the string following the option character in that element of argv<\/i>, and optind<\/i> shall be incremented by 1.<\/p>\n<\/td>\n<\/tr>\n<\/table>\n

If, when getopt<\/i>() is called:<\/p>\n

argv<\/i>[optind] is a null pointer
*argv<\/i>[optind] is not the character \u2212
argv<\/i>[optind] points to the string “\u2212”<\/p>\n

getopt<\/i>() shall return \u22121 without changing optind<\/i>. If:<\/p>\n

argv<\/i>[optind] points to the string “\u2212\u2212”<\/p>\n

getopt<\/i>() shall return \u22121 after incrementing optind<\/i>.<\/p>\n

If getopt<\/i>() encounters an option character that is not contained in optstring<\/i>, it shall return the (\u2019?\u2019<\/b>) character. If it detects a missing option-argument, it shall return the character (\u2019:\u2019<\/b>) if the first character of optstring<\/i> was a , or a character (\u2019?\u2019<\/b>) otherwise. In either case, getopt<\/i>() shall set the variable optopt<\/i> to the option character that caused the error. If the application has not set the variable opterr<\/i> to 0 and the first character of optstring<\/i> is not a , getopt<\/i>() shall also print a diagnostic message to stderr<\/i> in the format specified for the getopts<\/i> utility, unless the stderr<\/i> stream has wide orientation, in which case the behavior is undefined.<\/p>\n

The getopt<\/i>() function need not be thread-safe.<\/p>\n

RETURN VALUE <\/a> <\/h2>\n

The getopt<\/i>() function shall return the next option character specified on the command line.<\/p>\n

A (\u2019:\u2019<\/b>) shall be returned if getopt<\/i>() detects a missing argument and the first character of optstring<\/i> was a (\u2019:\u2019<\/b>).<\/p>\n

A (\u2019?\u2019<\/b>) shall be returned if getopt<\/i>() encounters an option character not in optstring<\/i> or detects a missing argument and the first character of optstring<\/i> was not a (\u2019:\u2019<\/b>).<\/p>\n

Otherwise, getopt<\/i>() shall return \u22121 when all command line options are parsed.<\/p>\n

ERRORS <\/a> <\/h2>\n

If the application has not set the variable opterr<\/i> to 0, the first character of optstring<\/i> is not a , and a write error occurs while getopt<\/i>() is printing a diagnostic message to stderr<\/i>, then the error indicator for stderr<\/i> shall be set; but getopt<\/i>() shall still succeed and the value of errno<\/i> after getopt<\/i>() is unspecified.<\/p>\n

The following sections are informative.<\/i><\/p>\n

EXAMPLES <\/a> <\/h2>\n

Parsing Command Line Options<\/b><\/i>
The following code fragment shows how you might process the arguments for a utility that can take the mutually-exclusive options a<\/i> and b<\/i> and the options f<\/i> and o<\/i>, both of which require arguments:<\/p>\n

#include
#include
#include <\/p>\n

int
main(int argc, char *argv[ ])
{
int c;
int bflg = 0, aflg = 0, errflg = 0;
char *ifile;
char *ofile;
. . .
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++;
break;
case ‘f’:
ifile = optarg;
break;
case ‘o’:
ofile = optarg;
break;
case ‘:’: \/bin \/boot \/dead.letter \/dev \/etc \/home \/initrd \/lib \/lib64 \/lost+found \/media \/mnt \/opt \/proc \/release-notes.html \/release-notes.txt \/root \/run \/sbin \/srv \/sys \/tmp \/usr \/var -f or -o without operand bodies\/ usr\/
fprintf(stderr,
“Option -%c requires an operandn”, optopt);
errflg++;
break;
case ‘?’:
fprintf(stderr,
“Unrecognized option: ‘-%c’n”, optopt);
errflg++;
}
}
if (errflg) {
fprintf(stderr, “usage: . . . “);
exit(2);
}
for ( ; optind < argc; optind++) {
if (access(argv[optind], R_OK)) {
. . .
}<\/p>\n

This code accepts any of the following as equivalent:<\/p>\n

cmd -ao arg path path
cmd -a -o arg path path
cmd -o arg -a path path
cmd -a -o arg — path path
cmd -a -oarg path path
cmd -aoarg path path<\/p>\n

Selecting Options from the Command Line<\/b>
The following example selects the type of database routines the user wants to use based on the Options<\/i> argument.<\/p>\n

#include
#include
…
const char *Options = “hdbtl”;
…
int dbtype, c;
char *st;
…
dbtype = 0;
while ((c = getopt(argc, argv, Options)) != -1) {
if ((st = strchr(Options, c)) != NULL) {
dbtype = st – Options;
break;
}
}<\/p>\n

APPLICATION USAGE <\/a> <\/h2>\n

The getopt<\/i>() function is only required to support option characters included in Utility Syntax Guideline 3. Many historical implementations of getopt<\/i>() support other characters as options. This is an allowed extension, but applications that use extensions are not maximally portable. Note that support for multi-byte option characters is only possible when such characters can be represented as type int<\/b>.<\/p>\n

Applications which use wide-character output functions with stderr<\/i> should ensure that any calls to getopt<\/i>() do not write to stderr<\/i>, either by setting opterr<\/i> to 0 or by ensuring the first character of optstring<\/i> is always a .<\/p>\n

While ferror<\/i>(stderr<\/i>) may be used to detect failures to write a diagnostic to stderr<\/i> when getopt<\/i>() returns \u2019?\u2019<\/b>, the value of errno<\/i> is unspecified in such a condition. Applications desiring more control over handling write failures should set opterr<\/i> to 0 and independently perform output to stderr<\/i>, rather than relying on getopt<\/i>() to do the output.<\/p>\n

RATIONALE <\/a> <\/h2>\n

The optopt<\/i> variable represents historical practice and allows the application to obtain the identity of the invalid option.<\/p>\n

The description has been written to make it clear that getopt<\/i>(), like the getopts<\/i> utility, deals with option-arguments whether separated from the option by characters or not. Note that the requirements on getopt<\/i>() and getopts<\/i> are more stringent than the Utility Syntax Guidelines.<\/p>\n

The getopt<\/i>() function shall return \u22121, rather than EOF, so that <\/i> is not required.<\/p>\n

The special significance of a as the first character of optstring<\/i> makes getopt<\/i>() consistent with the getopts<\/i> utility. It allows an application to make a distinction between a missing argument and an incorrect option letter without having to examine the option letter. It is true that a missing argument can only be detected in one case, but that is a case that has to be considered.<\/p>\n

FUTURE DIRECTIONS <\/a> <\/h2>\n

None.<\/p>\n

SEE ALSO <\/a> <\/h2>\n

exec<\/i><\/p>\n

The Base Definitions volume of POSIX.1-2017, Section 12.2<\/i>, Utility Syntax Guidelines<\/i>, <\/b><\/p>\n

The Shell and Utilities volume of POSIX.1-2017, getopts<\/i><\/p>\n

COPYRIGHT <\/a> <\/h2>\n

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology — Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http:\/\/www.opengroup.org\/unix\/online.html .<\/p>\n

Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https:\/\/www.kernel.org\/doc\/man-pages\/reporting_bugs.html .<\/p>\n

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