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2 <title>arg(3) - Plan 9 from User Space</title>

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6 <table border=0 cellpadding=0 cellspacing=0 width=100%>

7 <tr height=10><td>

8 <tr><td width=20><td>

9 <tr><td width=20><td><b>ARG(3)</b><td align=right><b>ARG(3)</b>

10 <tr><td width=20><td colspan=2>

11     <br>

12 <p><font size=+1><b>NAME     </b></font><br>

14 <table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>

16     ARGBEGIN, ARGEND, ARGC, ARGF, EARGF, arginit, argopt &ndash; process

17     option letters from argv<br>

19 </table>

20 <p><font size=+1><b>SYNOPSIS     </b></font><br>

22 <table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>

24     <tt><font size=+1>#include &lt;u.h&gt;<br>

25     #include &lt;libc.h&gt; 

26     <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>

27     </font></tt>

28     <tt><font size=+1>ARGBEGIN { <br>

29     char *ARGF(); <br>

30     char *EARGF(code); <br>

31     Rune ARGC(); <br>

32     } ARGEND <br>

34     <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>

35     </font></tt>

36     <tt><font size=+1>extern char *argv0; <br>

37     </font></tt>

38 </table>

39 <p><font size=+1><b>DESCRIPTION     </b></font><br>

41 <table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>

43     These macros assume the names <i>argc</i> and <i>argv</i> are in scope; see

44     <a href="../man3/exec.html"><i>exec</i>(3)</a>. <i>ARGBEGIN</i> and <i>ARGEND</i> surround code for processing program

45     options. The code should be the cases of a C switch on option

46     characters; it is executed once for each option character. Options

47     end after an argument <tt><font size=+1>&#8722;&#8722;</font></tt>, before an argument <tt><font size=+1>&#8722;</font></tt>, or

48     before an argument that doesn&#8217;t begin with <tt><font size=+1>&#8722;</font></tt>. 

49     <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>

51     The function macro <i>ARGC</i> returns the current option character,

52     as an integer. 

53     <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>

55     The function macro <i>ARGF</i> returns the current option argument: a

56     pointer to the rest of the option string if not empty, or the

57     next argument in <i>argv</i> if any, or 0. <i>ARGF</i> must be called just once

58     for each option that takes an argument. The macro <i>EARGF</i> is like

59     <i>ARGF</i> but instead of returning zero runs <i>code</i> and, if that

60     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>,

61     as in <tt><font size=+1>EARGF(usage())</font></tt>. 

62     <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>

64     After <i>ARGBEGIN</i>, <i>argv0</i> is a copy of <tt><font size=+1>argv[0]</font></tt> (conventionally the

65     name of the program). 

66     <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>

68     After <i>ARGEND</i>, <i>argv</i> points at a zero-terminated list of the remaining

69     <i>argc</i> arguments.<br>

71 </table>

72 <p><font size=+1><b>EXAMPLE     </b></font><br>

74 <table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>

76     This C program can take option <tt><font size=+1>b</font></tt> and option <tt><font size=+1>f</font></tt>, which requires

77     an argument.<br>

79     <table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>

81         <tt><font size=+1>#include &lt;u.h&gt;<br>

82         #include &lt;libc.h&gt;<br>

83         void<br>

84         main(int argc, char *argv[])<br>

85         {<br>

87         <table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>

89             char *f;<br>

90             print(&quot;%s&quot;, argv[0]);<br>

91             ARGBEGIN {<br>

92             case 'b':<br>

93              print(&quot; &#8722;b&quot;);<br>

94              break;<br>

95             case 'f':<br>

96              print(&quot; &#8722;f(%s)&quot;, (f=ARGF())? f: &quot;no arg&quot;);<br>

97              break;<br>

98             default:<br>

99              print(&quot; badflag('%c')&quot;, ARGC());<br>

100             } ARGEND<br>

101             print(&quot; %d args:&quot;, argc);<br>

102             while(*argv)<br>

103              print(&quot; '%s'&quot;, *argv++);<br>

104             print(&quot;\n&quot;);<br>

105             exits(nil);<br>

107         </table>

108         }<br>

110         <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>

111         </font></tt>

113     </table>

114     Here is the output from running the command <tt><font size=+1>prog &#8722;bffile1 &#8722;r &#8722;f

115     file2 arg1 arg2<br>

117     <table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>

119         prog &#8722;b &#8722;f(file1) badflag('r') &#8722;f(file2) 2 args: 'arg1' 'arg2'

121         <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>

123     </table>

124     </font></tt>

125     <table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>

129     </table>

131 </table>

132 <p><font size=+1><b>SOURCE     </b></font><br>

134 <table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>

136     <tt><font size=+1>/usr/local/plan9/include/libc.h<br>

137     </font></tt>

138 </table>

140 <td width=20>

141 <tr height=20><td>

142 </table>

143 <!-- TRAILER -->

144 <table border=0 cellpadding=0 cellspacing=0 width=100%>

145 <tr height=15><td width=10><td><td width=10>

146 <tr><td><td>

147 <center>

148 <a href="../../"><img src="../../dist/spaceglenda100.png" alt="Space Glenda" border=1></a>

149 </center>

150 </table>

151 <!-- TRAILER -->

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