arg(2) [plan9 man page]
ARG(2) System Calls Manual ARG(2) NAME
ARGBEGIN, ARGEND, ARGC, ARGF, arginit, argopt - process option letters from argv SYNOPSIS
#include <u.h> #include <libc.h> ARGBEGIN { char *ARGF(); Rune ARGC(); } ARGEND extern char *argv0; /* Alef only */ Arg *arginit(int argc, byte **argv); Rune argopt(Arg *arg); byte *argf(Arg *arg); DESCRIPTION
These macros assume the names argc and argv are in scope; see exec(2). ARGBEGIN and ARGEND surround code for processing program options. The code should be the cases of a C switch on option characters; it is executed once for each option character. Options end after an argu- ment --, before an argument -, or before an argument that doesn't begin with -. ARGC() returns the current option character. ARGF() returns the current option argument: a pointer to the rest of the option string if not empty, or the next argument in argv if any, or 0. ARGF must be called just once for each option that takes an argument. After ARGBEGIN, argv0 is a copy of argv[0] (conventionally the name of the program). After ARGEND, argv points at a zero-terminated list of the remaining argc arguments. Alef The Alef argument processing routines are unrelated. Instead, an aggr called Arg is initialized by a call to arginit. Successive calls to argopt return successive option characters, or zero at the end of the options. After a call to argopt, argf will return any argument string associated with the option. EXAMPLES
This C program can take option b and option f, which requires an argument. #include <u.h> #include <libc.h> void main(int argc, char *argv[]) { char *f; print("%s", argv[0]); ARGBEGIN { case 'b': print(" -b"); break; case 'f': print(" -f(%s)", (f=ARGF())? f: "no arg"); break; default: print(" badflag('%c')", ARGC()); } ARGEND print(" %d args:", argc); while(*argv) print(" '%s'", *argv++); print(" "); exits(0); } Here is the output for the run prog -bffile1 -r -f file2 arg1 arg2 prog -b -f(file1) badflag('r') -f(file2) 2 args: 'arg1' 'arg2' This Alef program accepts options b and, with an attached file name, f. #include <alef.h> void main(int argc, byte **argv) { int a, ac, bflag; byte *file; Arg *arg; arg = arginit(argc, argv); while(ac = argopt(arg)) switch(ac){ case 'b': bflag = 1; break; case 'f': file = argf(arg); break; } for(a=0; a<arg->ac; a++) print("argument %s ", arg->av[a]); } SOURCE
/sys/include/libc.h ARG(2)
Check Out this Related Man Page
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)