NAME

getflags, usage - process flag arguments in argv

SYNOPSIS

#include <libg.h>


 


#include <fb.h>


 


int getflags(int argc, char *argv[], char *flags)


 


int usage(char *tail)


 


extern char **flag[], cmdline[], *cmdname, *flagset[];

DESCRIPTION

Getflags digests an argument vector argv, finding flag arguments listed in flags. Flags is a string of flag letters. A letter followed by a colon and a number is expected to have the given number of parameters. A flag argument starts with `-' and is followed by any number of flag letters. A flag with one or more parameters must be the last flag in an argument. If any characters follow it, they are the flag's first parameter. Otherwise the following argument is the first parameter. Subsequent parameters are taken from subsequent arguments.

The global array flag is set to point to an array of parameters for each flag found. Thus, if flag -x was seen, flag['x'] is non-zero, and flag['x'][i] is the flag's ith parameter. If flag -x has no parameters flag['x']==flagset. Flags not found are marked with a zero. Flags and their parameters are deleted from argv. Getflags returns the adjusted argument count.

Getflags stops scanning for flags upon encountering a non-flag argument, or the argument --, which is deleted.

Getflags places a pointer to argv[0] in the external variable cmdname. It also concatenates the original members of argv, separated by spaces, and places the result in the external array cmdline.

Usage constructs a usage message, prints it on the standard error file, and exits with status 1. The command name printed is argv[0] Appropriate flag usage syntax is generated from flags. As an aid, explanatory information about flag parameters may be included in flags in square brackets as in the example. Tail is printed at the end of the message. If getflags encountered an error, usage tries to indicate the cause.

EXAMPLES

	main(int argc, char *argv[]){

		if((argc=getflags(argc, argv, "vinclbhse:1[expr]", 1))==-1)

			usage("[file ...]");

	}

might print:

	Illegal flag -u

	Usage: grep [-vinclbhs] [-e expr] [file ...]

SOURCE

/sys/src/libfb/getflags.c

SEE ALSO

arg(2)

DIAGNOSTICS

Getflags returns -1 on error: a syntax error in flags, setting a flag more than once, setting a flag not mentioned in flags, or running out of arguments while collecting a flag's parameters.