1GETOPT(3) Linux Programmer's Manual GETOPT(3)
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6 getopt, getopt_long, getopt_long_only, optarg, optind, opterr, optopt -
7 Parse command-line options
8
10 #include <unistd.h>
11 int getopt(int argc, char *const argv[],
13 const char *optstring);
14 extern char *optarg;
16 extern int optind, opterr, optopt;
17 #include <getopt.h>
19 int getopt_long(int argc, char *const argv[],
21 const char *optstring,
22 const struct option *longopts, int *longindex);
23 int getopt_long_only(int argc, char *const argv[],
24 const char *optstring,
25 const struct option *longopts, int *longindex);
26 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
28 getopt():
30 _POSIX_C_SOURCE >= 2 || _XOPEN_SOURCE
31 getopt_long(), getopt_long_only():
33 _GNU_SOURCE
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36 The getopt() function parses the command-line arguments. Its arguments
37 argc and argv are the argument count and array as passed to the main()
38 function on program invocation. An element of argv that starts with
39 '-' (and is not exactly "-" or "--") is an option element. The charac‐
40 ters of this element (aside from the initial '-') are option charac‐
41 ters. If getopt() is called repeatedly, it returns successively each
42 of the option characters from each of the option elements.
43 The variable optind is the index of the next element to be processed in
45 argv. The system initializes this value to 1. The caller can reset it
46 to 1 to restart scanning of the same argv, or when scanning a new argu‐
47 ment vector.
48 If getopt() finds another option character, it returns that character,
50 updating the external variable optind and a static variable nextchar so
51 that the next call to getopt() can resume the scan with the following
52 option character or argv-element.
53 If there are no more option characters, getopt() returns -1. Then
55 optind is the index in argv of the first argv-element that is not an
56 option.
57 optstring is a string containing the legitimate option characters. A
59 legitimate option character is any visible one byte ascii(7) character
60 (for which isgraph(3) would return nonzero) that is not '-' or ':'. If
61 such a character is followed by a colon, the option requires an argu‐
62 ment, so getopt() places a pointer to the following text in the same
63 argv-element, or the text of the following argv-element, in optarg.
64 Two colons mean an option takes an optional arg; if there is text in
65 the current argv-element (i.e., in the same word as the option name it‐
66 self, for example, "-oarg"), then it is returned in optarg, otherwise
67 optarg is set to zero. This is a GNU extension. If optstring contains
68 W followed by a semicolon, then -W foo is treated as the long option
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