STRCMP(P)						     POSIX Programmer's Manual							 STRCMP(P)

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() func-
       tion 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
");
		  }
	      }
	      ...

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 Technol-
       ogy -- 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 .

IEEE
/The Open Group						       2003								 STRCMP(P)