mirror of https://github.com/mkerrisk/man-pages
101 lines
3.0 KiB
Plaintext
101 lines
3.0 KiB
Plaintext
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.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
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.TH "STRCMP" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
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.\" strcmp
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.SH NAME
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strcmp \- compare two strings
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.SH SYNOPSIS
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.LP
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\fB#include <string.h>
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.br
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.sp
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int strcmp(const char *\fP\fIs1\fP\fB, const char *\fP\fIs2\fP\fB);
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.br
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\fP
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.SH DESCRIPTION
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.LP
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The \fIstrcmp\fP() function shall compare the string pointed to by
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\fIs1\fP to the string pointed to by \fIs2\fP.
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.LP
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The sign of a non-zero return value shall be determined by the sign
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of the difference between the values of the first pair of
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bytes (both interpreted as type \fBunsigned char\fP) that differ in
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the strings being compared.
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.SH RETURN VALUE
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.LP
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Upon completion, \fIstrcmp\fP() shall return an integer greater than,
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equal to, or less than 0, if the string pointed to by
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\fIs1\fP is greater than, equal to, or less than the string pointed
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to by \fIs2\fP, respectively.
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.SH ERRORS
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.LP
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No errors are defined.
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.LP
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\fIThe following sections are informative.\fP
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.SH EXAMPLES
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.SS Checking a Password Entry
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.LP
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The following example compares the information read from standard
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input to the value of the name of the user entry. If the
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\fIstrcmp\fP() function returns 0 (indicating a match), a further
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check will be made to see if the user entered the proper old
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password. The \fIcrypt\fP() function shall encrypt the old password
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entered by the user,
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using the value of the encrypted password in the \fBpasswd\fP structure
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as the salt. If this value matches the value of the
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encrypted \fBpasswd\fP in the structure, the entered password \fIoldpasswd\fP
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is the correct user's password. Finally, the
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program encrypts the new password so that it can store the information
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in the \fBpasswd\fP structure.
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.sp
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.RS
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.nf
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\fB#include <string.h>
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#include <unistd.h>
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#include <stdio.h>
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\&...
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int valid_change;
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struct passwd *p;
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char user[100];
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char oldpasswd[100];
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char newpasswd[100];
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char savepasswd[100];
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\&...
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if (strcmp(p->pw_name, user) == 0) {
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if (strcmp(p->pw_passwd, crypt(oldpasswd, p->pw_passwd)) == 0) {
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strcpy(savepasswd, crypt(newpasswd, user));
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p->pw_passwd = savepasswd;
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valid_change = 1;
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}
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else {
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fprintf(stderr, "Old password is not valid\\n");
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}
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}
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\&...
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\fP
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.fi
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.RE
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.SH APPLICATION USAGE
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.LP
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None.
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.SH RATIONALE
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.LP
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None.
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.SH FUTURE DIRECTIONS
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.LP
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None.
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.SH SEE ALSO
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.LP
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\fIstrncmp\fP() , the Base Definitions volume of IEEE\ Std\ 1003.1-2001,
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\fI<string.h>\fP
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.SH COPYRIGHT
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Portions of this text are reprinted and reproduced in electronic form
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from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
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-- Portable Operating System Interface (POSIX), The Open Group Base
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Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
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Electrical and Electronics Engineers, Inc and The Open Group. In the
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event of any discrepancy between this version and the original IEEE and
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The Open Group Standard, the original IEEE and The Open Group Standard
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is the referee document. The original Standard can be obtained online at
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http://www.opengroup.org/unix/online.html .
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