Sams Teach Yourself C in 21 Days

Manipulating Strings 491

17

Comparing Two Entire Strings ......................................................................

The function strcmp()compares two strings, character by character. Its prototype is

int strcmp(const char *str1, const char *str2);

The arguments str1andstr2are pointers to the strings being compared. The function’s

return values are given in Table 17.1. You should notice that both strings are past as con-

stants because neither will be changed. Listing 17.7 demonstrates strcmp().

TABLE17.1 The values returned by strcmp()

Return Value Meaning

< 0 str1is less than str2.

0 str1is equal to str2.

> 0 str1is greater than str2.

LISTING17.7 strcmp.c. Using strcmp()to compare strings

1: /* The strcmp() function. */

2:

3: #include <stdio.h>

4: #include <string.h>

5:

6: int main( void )

7: {

8: char str1[80], str2[80];

9: int x;

10:

11: while (1)

12: {

13:

14: /* Input two strings. */

15:

16: printf(“\n\nInput the first string, a blank to exit: “);

17: gets(str1);

18:

19: if ( strlen(str1) == 0 )

20: break;

21:

22: printf(“\nInput the second string: “);

23: gets(str2);

24:

25: /* Compare them and display the result. */

26:

27: x = strcmp(str1, str2);

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