ARG(2)

NAME

ARG − process option letters from argv

SYNOPSIS

#include <libc.h>
ARGBEGIN {
} ARGEND
char ∗ARGF();
Rune ARGC();

extern char ∗argv0;

DESCRIPTION

Command-line arguments to programs (see exec(2)) are conventionally arranged as a set of options — strings beginning with a - (minus sign) — followed by plain arguments such as file names. The ARG macros provide a convenient means for processing these options. Option characters appear in nonempty clusters preceded by -. After options processing is terminated (by an argument not starting with -, or by the argument -- which is then skipped, or by the argument -), execution resumes after the ARGEND.

The body of a switch statement should be put between ARGBEGIN{ and }ARGEND; it is executed once for each option character (the character itself may be referenced by ARGC()). If an option takes a string argument (that is, the rest of the current option string or if that is empty, the next argument), it can be referenced by ARGF(). After ARGEND, argv points at a zero-terminated list of the remaining argc arguments.

ARGBEGIN also sets up argv0 to point at argv[0] (conventionally the name of the program).

EXAMPLES

This program processes arguments for a command that can take option b and option f, which requires an argument.

#include <u.h>
#include <libc.h>
main(int argc, char ∗argv[])
{
char ∗f;
print("%s", argv[0]);
ARGBEGIN{
case ’b’:print(" -b"); break;
case ’f’:f = ARGF(); print(" -f(%s)", f?f:"no arg"); break;
default:print(" badflag(’%c’)", ARGC()); break;
}ARGEND
print(" %d args:", argc);
while(∗argv)
print(" ’%s’", ∗argv++);
print("\n");
exits(0);
}

When this program is run as

prog -bffile1 -r -f file2 arg1 argn

it yields

prog -b -f(file1) badflag(’r’) -f(file2) 2 args: ’arg1’ ’argn’

DIAGNOSTICS

ARGF() returns 0 on error.