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Full Discussion: _getopt function
Top Forums Programming _getopt function Post 19278 by killerserv on Monday 8th of April 2002 08:17:23 PM
Old 04-08-2002
Windows/Dos commands? I think you are mistaken , this is a Unix Q&A Forum. How you want a windows command ?

This is a small definition of get_ops() function on Unix C
get_opt() - get options/arguments from command line argument list. The get_opt() function parses a command line argument list argv seeking for command arguments, option characters/strings and option arguments.
An option character is known if it has been specified in the string of accepted option characters, optstring . optstring may contain the following elements: individual characters, and characters followed by a colon to indicate an option argument is to follow. For example, an option string " x &qout; recognizes an option " -x ", and an option string "x:" recognizes an option and argument " -x argument ". If command argument is recognized get_opt() returns NULL , and optarg points to an argument. If known option character is recognized get_opt() returns option character itself and optarg points to an option argument, if it is anticipated. If current option character is unknown or if current option character demands argument but there is no anticipated argument or if option character is equal to '?' then return value is '?'. When the argument list is exhausted the get_opt() function returns an EOF . It's possible to check for long option by specifying correspondence between option character and option string optname using set_long_opt().

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getopt(3C)																getopt(3C)

getopt(), optarg, opterr, optind, optopt - get option letter from argument vector SYNOPSIS
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

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