How to Use strcmp in C: Syntax, Example, and Tips

In C, use strcmp to compare two strings by passing their pointers to the function. It returns 0 if the strings are equal, a negative value if the first string is less, and a positive value if the first string is greater.

Syntax

The strcmp function compares two strings character by character.

• int strcmp(const char *str1, const char *str2);
• str1 and str2 are pointers to the strings to compare.
• Returns 0 if both strings are equal.
• Returns a negative value if str1 is less than str2.
• Returns a positive value if str1 is greater than str2.

c

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

Example

This example shows how to compare two strings using strcmp and print the result.

c

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

int main() {
    const char *a = "apple";
    const char *b = "banana";

    int result = strcmp(a, b);

    if (result == 0) {
        printf("Strings are equal.\n");
    } else if (result < 0) {
        printf("'%s' is less than '%s'.\n", a, b);
    } else {
        printf("'%s' is greater than '%s'.\n", a, b);
    }

    return 0;
}

Output

'apple' is less than 'banana'.

Common Pitfalls

Common mistakes when using strcmp include:

• Using == to compare strings instead of strcmp. This compares pointers, not content.
• Not checking the return value properly (only checking for equality, ignoring less or greater).
• Passing uninitialized or NULL pointers to strcmp, which causes undefined behavior.

c

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

int main() {
    const char *str1 = "hello";
    const char *str2 = "hello";

    // Wrong: compares addresses, not string content
    if (str1 == str2) {
        printf("Wrong: Strings are equal.\n");
    } else {
        printf("Wrong: Strings are not equal.\n");
    }

    // Right: use strcmp to compare content
    if (strcmp(str1, str2) == 0) {
        printf("Right: Strings are equal.\n");
    } else {
        printf("Right: Strings are not equal.\n");
    }

    return 0;
}

Output

Wrong: Strings are not equal.
Right: Strings are equal.

Quick Reference

Return Value	Meaning
0	Strings are equal
< 0	First string is less than second string
> 0	First string is greater than second string

Key Takeaways

Use strcmp to compare string contents, not the == operator.

strcmp returns 0 if strings match exactly.

Check if strcmp result is less than or greater than zero to know order.

Never pass NULL pointers to strcmp to avoid crashes.

Always include to use strcmp.