.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "STRCMP" 3P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\" strcmp 
.SH PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
.SH NAME
strcmp \- compare two strings
.SH SYNOPSIS
.LP
\fB#include <string.h>
.br
.sp
int strcmp(const char *\fP\fIs1\fP\fB, const char *\fP\fIs2\fP\fB);
.br
\fP
.SH DESCRIPTION
.LP
The \fIstrcmp\fP() function shall compare the string pointed to by
\fIs1\fP to the string pointed to by \fIs2\fP.
.LP
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 \fBunsigned char\fP) that differ in
the strings being compared.
.SH RETURN VALUE
.LP
Upon completion, \fIstrcmp\fP() shall return an integer greater than,
equal to, or less than 0, if the string pointed to by
\fIs1\fP is greater than, equal to, or less than the string pointed
to by \fIs2\fP, respectively.
.SH ERRORS
.LP
No errors are defined.
.LP
\fIThe following sections are informative.\fP
.SH EXAMPLES
.SS Checking a Password Entry
.LP
The following example compares the information read from standard
input to the value of the name of the user entry. If the
\fIstrcmp\fP() function returns 0 (indicating a match), a further
check will be made to see if the user entered the proper old
password. The \fIcrypt\fP() function shall encrypt the old password
entered by the user,
using the value of the encrypted password in the \fBpasswd\fP structure
as the salt. If this value matches the value of the
encrypted \fBpasswd\fP in the structure, the entered password \fIoldpasswd\fP
is the correct user's password. Finally, the
program encrypts the new password so that it can store the information
in the \fBpasswd\fP structure.
.sp
.RS
.nf

\fB#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");
    }
}
\&...
\fP
.fi
.RE
.SH APPLICATION USAGE
.LP
None.
.SH RATIONALE
.LP
None.
.SH FUTURE DIRECTIONS
.LP
None.
.SH SEE ALSO
.LP
\fIstrncmp\fP(), the Base Definitions volume of IEEE\ Std\ 1003.1-2001,
\fI<string.h>\fP
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .