getopt(3) [minix man page]
GETOPT(3) Library Functions Manual GETOPT(3) NAME
getopt - get option letter from argv SYNOPSIS
int getopt(argc, argv, optstring) int argc; char **argv; char *optstring; extern char *optarg; extern int optind; DESCRIPTION
Getopt returns the next option letter in argv that matches a letter in optstring. 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. Optarg is set to point to the start of the option argument on return from getopt. Getopt places in optind the argv index of the next argument to be processed. Because optind is external, it is normally initialized to zero automatically before the first call to getopt. When all options have been processed (i.e., up to the first non-option argument), getopt returns EOF. The special option -- may be used to delimit the end of the options; EOF will be returned, and -- will be skipped. DIAGNOSTICS
Getopt prints an error message on stderr and returns a question mark (?) when it encounters an option letter not included in optstring. EXAMPLE
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: main(argc, argv) int argc; char **argv; { int c; extern int optind; 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; break; case `?': default: errflg++; break; } if (errflg) { fprintf(stderr, "Usage: ..."); exit(2); } for (; optind < argc; optind++) { . . . } . . . } HISTORY
Written by Henry Spencer, working from a Bell Labs manual page. Modified by Keith Bostic to behave more like the System V version. BUGS
It is not obvious how `-' standing alone should be treated; this version treats it as a non-option argument, which is not always right. Option arguments are allowed to begin with `-'; this is reasonable but reduces the amount of error checking possible. Getopt is quite flexible but the obvious price must be paid: there is much it could do that it doesn't, like checking mutually exclusive options, checking type of option arguments, etc. 4.3 Berkeley Distribution May 27, 1986 GETOPT(3)
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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)