157 lines
5.3 KiB
HTML
157 lines
5.3 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
|
<html>
|
|
<head>
|
|
<meta name="generator" content="HTML Tidy, see www.w3.org">
|
|
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
|
<link type="text/css" rel="stylesheet" href="style.css"><!-- Generated by The Open Group's rhtm tool v1.2.1 -->
|
|
<!-- Copyright (c) 2001 The Open Group, All Rights Reserved -->
|
|
<title>strcmp</title>
|
|
</head>
|
|
<body bgcolor="white">
|
|
<script type="text/javascript" language="JavaScript" src="../jscript/codes.js">
|
|
</script>
|
|
|
|
<basefont size="3"> <a name="strcmp"></a> <a name="tag_03_722"></a><!-- strcmp -->
|
|
<!--header start-->
|
|
<center><font size="2">The Open Group Base Specifications Issue 6<br>
|
|
IEEE Std 1003.1-2001<br>
|
|
Copyright © 2001 The IEEE and The Open Group, All Rights reserved.</font></center>
|
|
|
|
<!--header end-->
|
|
<hr size="2" noshade>
|
|
<h4><a name="tag_03_722_01"></a>NAME</h4>
|
|
|
|
<blockquote>strcmp - compare two strings</blockquote>
|
|
|
|
<h4><a name="tag_03_722_02"></a>SYNOPSIS</h4>
|
|
|
|
<blockquote class="synopsis">
|
|
<p><code><tt>#include <<a href="../basedefs/string.h.html">string.h</a>><br>
|
|
<br>
|
|
int strcmp(const char *</tt><i>s1</i><tt>, const char *</tt><i>s2</i><tt>);<br>
|
|
</tt></code></p>
|
|
</blockquote>
|
|
|
|
<h4><a name="tag_03_722_03"></a>DESCRIPTION</h4>
|
|
|
|
<blockquote>
|
|
<div class="box"><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]"
|
|
border="0"> The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the
|
|
requirements described here and the ISO C standard is unintentional. This volume of IEEE Std 1003.1-2001 defers to
|
|
the ISO C standard. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></div>
|
|
|
|
<p>The <i>strcmp</i>() function shall compare the string pointed to by <i>s1</i> to the string pointed to by <i>s2</i>.</p>
|
|
|
|
<p>The sign of a non-zero return value shall be determined by the sign of the difference between the values of the first pair of
|
|
bytes (both interpreted as type <b>unsigned char</b>) that differ in the strings being compared.</p>
|
|
</blockquote>
|
|
|
|
<h4><a name="tag_03_722_04"></a>RETURN VALUE</h4>
|
|
|
|
<blockquote>
|
|
<p>Upon completion, <i>strcmp</i>() shall return an integer greater than, equal to, or less than 0, if the string pointed to by
|
|
<i>s1</i> is greater than, equal to, or less than the string pointed to by <i>s2</i>, respectively.</p>
|
|
</blockquote>
|
|
|
|
<h4><a name="tag_03_722_05"></a>ERRORS</h4>
|
|
|
|
<blockquote>
|
|
<p>No errors are defined.</p>
|
|
</blockquote>
|
|
|
|
<hr>
|
|
<div class="box"><em>The following sections are informative.</em></div>
|
|
|
|
<h4><a name="tag_03_722_06"></a>EXAMPLES</h4>
|
|
|
|
<blockquote>
|
|
<h5><a name="tag_03_722_06_01"></a>Checking a Password Entry</h5>
|
|
|
|
<p>The following example compares the information read from standard input to the value of the name of the user entry. If the
|
|
<i>strcmp</i>() function returns 0 (indicating a match), a further check will be made to see if the user entered the proper old
|
|
password. The <a href="../functions/crypt.html"><i>crypt</i>()</a> function shall encrypt the old password entered by the user,
|
|
using the value of the encrypted password in the <b>passwd</b> structure as the salt. If this value matches the value of the
|
|
encrypted <b>passwd</b> in the structure, the entered password <i>oldpasswd</i> is the correct user's password. Finally, the
|
|
program encrypts the new password so that it can store the information in the <b>passwd</b> structure.</p>
|
|
|
|
<pre>
|
|
<tt>#include <string.h>
|
|
#include <unistd.h>
|
|
#include <stdio.h>
|
|
...
|
|
int valid_change;
|
|
struct passwd *p;
|
|
char user[100];
|
|
char oldpasswd[100];
|
|
char newpasswd[100];
|
|
char savepasswd[100];
|
|
...
|
|
if (strcmp(p->pw_name, user) == 0) {
|
|
if (strcmp(p->pw_passwd, crypt(oldpasswd, p->pw_passwd)) == 0) {
|
|
strcpy(savepasswd, crypt(newpasswd, user));
|
|
p->pw_passwd = savepasswd;
|
|
valid_change = 1;
|
|
}
|
|
else {
|
|
fprintf(stderr, "Old password is not valid\n");
|
|
}
|
|
}
|
|
...
|
|
</tt>
|
|
</pre>
|
|
</blockquote>
|
|
|
|
<h4><a name="tag_03_722_07"></a>APPLICATION USAGE</h4>
|
|
|
|
<blockquote>
|
|
<p>None.</p>
|
|
</blockquote>
|
|
|
|
<h4><a name="tag_03_722_08"></a>RATIONALE</h4>
|
|
|
|
<blockquote>
|
|
<p>None.</p>
|
|
</blockquote>
|
|
|
|
<h4><a name="tag_03_722_09"></a>FUTURE DIRECTIONS</h4>
|
|
|
|
<blockquote>
|
|
<p>None.</p>
|
|
</blockquote>
|
|
|
|
<h4><a name="tag_03_722_10"></a>SEE ALSO</h4>
|
|
|
|
<blockquote>
|
|
<p><a href="strncmp.html"><i>strncmp</i>()</a> , the Base Definitions volume of IEEE Std 1003.1-2001, <a href=
|
|
"../basedefs/string.h.html"><i><string.h></i></a></p>
|
|
</blockquote>
|
|
|
|
<h4><a name="tag_03_722_11"></a>CHANGE HISTORY</h4>
|
|
|
|
<blockquote>
|
|
<p>First released in Issue 1. Derived from Issue 1 of the SVID.</p>
|
|
</blockquote>
|
|
|
|
<h4><a name="tag_03_722_12"></a>Issue 6</h4>
|
|
|
|
<blockquote>
|
|
<p>Extensions beyond the ISO C standard are marked.</p>
|
|
</blockquote>
|
|
|
|
<div class="box"><em>End of informative text.</em></div>
|
|
|
|
<hr>
|
|
<hr size="2" noshade>
|
|
<center><font size="2"><!--footer start-->
|
|
UNIX ® is a registered Trademark of The Open Group.<br>
|
|
POSIX ® is a registered Trademark of The IEEE.<br>
|
|
[ <a href="../mindex.html">Main Index</a> | <a href="../basedefs/contents.html">XBD</a> | <a href=
|
|
"../utilities/contents.html">XCU</a> | <a href="../functions/contents.html">XSH</a> | <a href="../xrat/contents.html">XRAT</a>
|
|
]</font></center>
|
|
|
|
<!--footer end-->
|
|
<hr size="2" noshade>
|
|
</body>
|
|
</html>
|
|
|