SAS/C Library Reference, Vol. 1

strncmp -- Compare Portions of Two Strings

SYNOPSIS

 #include <string.h>

 int strncmp(const char *str1, const char *str2,
             size_t maxlen);

DESCRIPTION

strncmp compares two character strings (str1 and str2) using the standard EBCDIC collating sequence. The return value has the same relationship to 0 as str1 has to str2. If two strings are equal up to the point at which one terminates (that is, contains a null character), the longer string is considered greater. If maxlen characters are inspected from each string and no inequality is detected, the strings are considered equal.

RETURN VALUE

The return value from strncmp is 0 if the two strings are equal, less than 0 if str1 compares less than str2, and greater than 0 if str1 compares greater than str2 (within the first maxlen characters). No other assumptions should be made about the value returned by strncmp.

CAUTION

If the maxlen value is specified as 0, a result of 0 is returned. If the value is a negative integer, it is interpreted as a very large unsigned value. This may cause a protection or addressing exception, but this is unlikely because comparison ceases as soon as unequal characters are found.

IMPLEMENTATION

strncmp is implemented as a built-in function, unless you use it with undef.

EXAMPLE

Compare this example to the example for strcmp:

  #include <string.h>
  #include <stdio.h>
  #include <stdlib.h>

  main()
  {
     char command[20];
     int n = 0;

     do{
        n++;
         printf("You have executed this loop %d times.n", n);

         puts("Enter quit(may be abbreviated) to end program,");
         puts(" or any other command to continue.");
         gets(command);
     }
     while(strncmp(command, "quit", strlen(command)) != 0);
     exit(0);
  }

RELATED FUNCTIONS

memcmp, strcmp