NAME

       strcmp - compare two strings

SYNOPSIS

       #include <string.h>

       int strcmp(const char *s1, const char *s2);

DESCRIPTION

       The  strcmp()  function shall compare the string pointed to by s1 to the string pointed to
       by s2.

       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 unsigned char)
       that differ in the strings being compared.

RETURN VALUE

       Upon completion, strcmp() shall return an integer greater than, equal to, or less than  0,
       if  the string pointed to by s1 is greater than, equal to, or less than the string pointed
       to by s2, respectively.

ERRORS

       No errors are defined.

       The following sections are informative.

EXAMPLES

   Checking a Password Entry
       The following example compares the information read from standard input to  the  value  of
       the  name  of  the  user entry. If the strcmp() function returns 0 (indicating a match), a
       further check will be made to see if the user entered the proper old password. The crypt()
       function  shall  encrypt  the  old  password  entered  by the user, using the value of the
       encrypted password in the passwd structure as the salt. If this value matches the value of
       the  encrypted  passwd  in  the  structure,  the entered password oldpasswd is the correct
       user's password. Finally, the program encrypts the new password so that it can  store  the
       information in the passwd structure.

              #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");
                  }
              }
              ...

APPLICATION USAGE

       None.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       strncmp() , the Base Definitions volume of IEEE Std 1003.1-2001, <string.h>

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 .