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)
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GETOPT(3) Library Functions Manual GETOPT(3) NAME
getopt - get option character from command line argument list SYNOPSIS
#include <stdlib.h> extern char *optarg; extern int optind; extern int optopt; extern int opterr; extern int optreset; int getopt(argc, argv, optstring) int argc; char **argv; char *optstring; DESCRIPTION
The getopt() function incrementally parses a command line argument list argv and returns the next known option character. An option char- acter is known if it has been specified in the string of accepted option characters, optstring. The option string 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"" recognizes an option ``-x'', and an option string """x:"" recognizes an option and argument ``-x argument''. It does not matter to getopt() if a following argument has leading white space. On return from getopt(), optarg points to an option argument, if it is anticipated, and the variable optind contains the index to the next argv argument for a subsequent call to getopt(). The variable optopt saves the last known option character returned by getopt(). The variable opterr and optind are both initialized to 1. The optind variable may be set to another value before a set of calls to getopt() in order to skip over more or less argv entries. In order to use getopt() to evaluate multiple sets of arguments, or to evaluate a single set of arguments multiple times, the variable optreset must be set to 1 before the second and each additional set of calls to getopt(), and the variable optind must be reinitialized. The getopt() function returns an EOF when the argument list is exhausted, or a non-recognized option is encountered. The interpretation of options in the argument list may be cancelled by the option `--' (double dash) which causes getopt() to signal the end of argument process- ing and return an EOF. When all options have been processed (i.e., up to the first non-option argument), getopt() returns EOF. DIAGNOSTICS
If the getopt() function encounters a character not found in the string optarg or detects a missing option argument it writes an error mes- sage and returns `?' to the stderr. Setting opterr to a zero will disable these error messages. If optstring has a leading `:' then a missing option argument causes a `:' to be returned in addition to suppressing any error messages. Option arguments are allowed to begin with `-'; this is reasonable but reduces the amount of error checking possible. EXTENSIONS
The optreset variable was added to make it possible to call the getopt() function multiple times. This is an extension to the IEEE Std1003.2 (``POSIX'') specification. EXAMPLE
extern char *optarg; extern int optind; int bflag, ch, fd; bflag = 0; while ((ch = getopt(argc, argv, "bf:")) != EOF) switch(ch) { case 'b': bflag = 1; break; case 'f': if ((fd = open(optarg, O_RDONLY, 0)) < 0) { (void)fprintf(stderr, "myname: %s: %s ", optarg, strerror(errno)); exit(1); } break; case '?': default: usage(); } argc -= optind; argv += optind; HISTORY
The getopt() function appeared 4.3BSD. BUGS
A single dash ``-'' may be specified as an character in optstring , however it should never have an argument associated with it. This allows getopt() to be used with programs that expect ``-'' as an option flag. This practice is wrong, and should not be used in any cur- rent development. It is provided for backward compatibility only . By default, a single dash causes getopt() to return EOF. This is, we believe, compatible with System V. It is also possible to handle digits as option letters. This allows getopt() to be used with programs that expect a number (``-3'') as an option. This practice is wrong, and should not be used in any current development. It is provided for backward compatibility only. The following code fragment works in most cases. int length; char *p; while ((c = getopt(argc, argv, "0123456789")) != EOF) switch (c) { case '0': case '1': case '2': case '3': case '4': case '5': case '6': case '7': case '8': case '9': p = argv[optind - 1]; if (p[0] == '-' && p[1] == ch && !p[2]) length = atoi(++p); else length = atoi(argv[optind] + 1); break; } } 4.3 Berkeley Distribution January 12, 1996 GETOPT(3)