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<head>
<title>arg(3) - Plan 9 from User Space</title>
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<tr><td width=20><td><b>ARG(3)</b><td align=right><b>ARG(3)</b>
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<br>
<p><font size=+1><b>NAME </b></font><br>
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ARGBEGIN, ARGEND, ARGC, ARGF, EARGF, arginit, argopt – process
option letters from argv<br>
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<p><font size=+1><b>SYNOPSIS </b></font><br>
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<tt><font size=+1>#include <u.h><br>
#include <libc.h>
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<tt><font size=+1>ARGBEGIN { <br>
char *ARGF(); <br>
char *EARGF(code); <br>
Rune ARGC(); <br>
} ARGEND <br>
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</font></tt>
<tt><font size=+1>extern char *argv0; <br>
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<p><font size=+1><b>DESCRIPTION </b></font><br>
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These macros assume the names <i>argc</i> and <i>argv</i> are in scope; see
<a href="../man3/exec.html"><i>exec</i>(3)</a>. <i>ARGBEGIN</i> and <i>ARGEND</i> 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 argument <tt><font size=+1>−−</font></tt>, before an argument <tt><font size=+1>−</font></tt>, or
before an argument that doesn’t begin with <tt><font size=+1>−</font></tt>.
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The function macro <i>ARGC</i> returns the current option character,
as an integer.
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The function macro <i>ARGF</i> returns the current option argument: a
pointer to the rest of the option string if not empty, or the
next argument in <i>argv</i> if any, or 0. <i>ARGF</i> must be called just once
for each option that takes an argument. The macro <i>EARGF</i> is like
<i>ARGF</i> but instead of returning zero runs <i>code</i> and, if that
returns, calls <a href="../man3/abort.html"><i>abort</i>(3)</a>. A typical value for <i>code</i> is <tt><font size=+1>usage()</font></tt>,
as in <tt><font size=+1>EARGF(usage())</font></tt>.
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After <i>ARGBEGIN</i>, <i>argv0</i> is a copy of <tt><font size=+1>argv[0]</font></tt> (conventionally the
name of the program).
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After <i>ARGEND</i>, <i>argv</i> points at a zero-terminated list of the remaining
<i>argc</i> arguments.<br>
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<p><font size=+1><b>EXAMPLE </b></font><br>
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This C program can take option <tt><font size=+1>b</font></tt> and option <tt><font size=+1>f</font></tt>, which requires
an argument.<br>
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<tt><font size=+1>#include <u.h><br>
#include <libc.h><br>
void<br>
main(int argc, char *argv[])<br>
{<br>
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char *f;<br>
print("%s", argv[0]);<br>
ARGBEGIN {<br>
case 'b':<br>
print(" −b");<br>
break;<br>
case 'f':<br>
print(" −f(%s)", (f=ARGF())? f: "no arg");<br>
break;<br>
default:<br>
print(" badflag('%c')", ARGC());<br>
} ARGEND<br>
print(" %d args:", argc);<br>
while(*argv)<br>
print(" '%s'", *argv++);<br>
print("\n");<br>
exits(nil);<br>
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}<br>
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</font></tt>
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Here is the output from running the command <tt><font size=+1>prog −bffile1 −r −f
file2 arg1 arg2<br>
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prog −b −f(file1) badflag('r') −f(file2) 2 args: 'arg1' 'arg2'
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</font></tt>
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<p><font size=+1><b>SOURCE </b></font><br>
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<tt><font size=+1>/usr/local/plan9/include/libc.h<br>
</font></tt>
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<center>
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