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.TH ARG 2
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.SH NAME
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ARGBEGIN, ARGEND, ARGC, ARGF, EARGF \- process option letters from argv
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.SH SYNOPSIS
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.B #include <u.h>
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.br
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.B #include <libc.h>
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.PP
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.nf
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.B ARGBEGIN {
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.B char *ARGF();
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.B char *EARGF(code);
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.B Rune ARGC();
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.B } ARGEND
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.PP
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.B extern char *argv0;
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.SH DESCRIPTION
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These macros assume the names
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.I argc
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and
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.I argv
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are in scope; see
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.IR exec (2).
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.I ARGBEGIN
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and
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.I ARGEND
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surround code for processing program options.
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The code
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should be the cases of a C switch on
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option characters;
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it is executed once for each option character.
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Options end after an argument
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.BR -- ,
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before an argument
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.BR - ,
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or before an argument that doesn't begin with
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.BR - .
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.PP
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The function macro
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.I ARGC
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returns the current option character, as an integer.
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.PP
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The function macro
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.I ARGF
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returns the current option argument:
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a pointer to the rest of the option string if not empty,
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or the next argument in
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.I argv
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if any, or 0.
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.I ARGF
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must be called just once for each option
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argument.
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The macro
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.I EARGF
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is like
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.I ARGF
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but instead of returning zero
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runs
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.I code
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and, if that returns, calls
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.IR abort (2).
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A typical value for
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.I code
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is
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.BR usage() ,
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as in
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.BR EARGF(usage()) .
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.PP
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After
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.IR ARGBEGIN ,
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.I argv0
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is a copy of
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.BR argv[0]
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(conventionally the name of the program).
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.PP
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After
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.IR ARGEND ,
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.I argv
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points at a zero-terminated list of the remaining
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.I argc
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arguments.
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.SH EXAMPLE
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This C program can take option
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.B b
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and option
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.BR f ,
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which requires an argument.
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.IP
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.EX
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.ta \w'12345678'u +\w'12345678'u +\w'12345678'u +\w'12345678'u +\w'12345678'u
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#include <u.h>
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#include <libc.h>
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void
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main(int argc, char *argv[])
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{
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	char *f;
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	print("%s", argv[0]);
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	ARGBEGIN {
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	case 'b':
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		print(" -b");
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		break;
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	case 'f':
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		print(" -f(%s)", (f=ARGF())? f: "no arg");
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		break;
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	default:
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		print(" badflag('%c')", ARGC());
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	} ARGEND
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	print(" %d args:", argc);
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	while(*argv)
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		print(" '%s'", *argv++);
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	print("\en");
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	exits(nil);
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}
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.EE
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.PP
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Here is the output from running the command
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.B
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prog -bffile1 -r -f file2 arg1 arg2
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.IP
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.B
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prog -b -f(file1) badflag('r') -f(file2) 2 args: 'arg1' 'arg2'
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.PP
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.SH SOURCE
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.B /sys/include/libc.h
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.SH SEE ALSO
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.IR getflags (8)