term% cat index.txt ARG(2) System Calls Manual ARG(2)
NAME
ARGBEGIN, ARGEND, ARGC, ARGF, EARGF - process option letters from argv
SYNOPSIS
#include <u.h>
#include <libc.h>
ARGBEGIN {
char *ARGF();
char *EARGF(code);
Rune ARGC();
} ARGEND
extern char *argv0;
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 exe‐
cuted once for each option character. Options end after an argument
--, before an argument -, or before an argument that doesn't begin with
-.
The function macro ARGC returns the current option character, as an in‐
teger.
The function macro 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 argu‐
ment. The macro EARGF is like ARGF but instead of returning zero runs
code and, if that returns, calls abort(2). A typical value for code is
usage(), as in EARGF(usage()).
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.
EXAMPLE
This C program can take option b and option f, which requires an argu‐
ment.
#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("\n");
exits(nil);
}
Here is the output from running the command prog -bffile1 -r -f file2
arg1 arg2
prog -b -f(file1) badflag('r') -f(file2) 2 args: 'arg1' 'arg2'
SOURCE
/sys/include/libc.h
SEE ALSO
getflags(8)
ARG(2)