strcat() in C: Concatenate Strings

strcat() appends the complete source string to the end of a destination string. The destination array must already contain a valid null-terminated string and must have enough unused capacity for the result.

Syntax Top ↑

strcat(destination, source);

Basic strcat() Example Top ↑

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

int main(void) {
    char destination[30] = "welcome to ";
    char source[] = "plus2net";

    strcat(destination, source);
    printf("%s\n", destination);
    return 0;
}

Output

welcome to plus2net

Append More Than One String Top ↑

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

int main(void) {
    char message[60] = "Learn ";

    strcat(message, "C ");
    strcat(message, "programming ");
    strcat(message, "with plus2net.");

    printf("%s\n", message);
    return 0;
}

Check Capacity Before Concatenating Top ↑

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

int main(void) {
    char destination[20] = "C: ";
    char source[] = "strings";
    size_t required = strlen(destination) + strlen(source) + 1;

    if (required <= sizeof(destination)) {
        strcat(destination, source);
        printf("%s\n", destination);
    } else {
        printf("Destination is too small.\n");
    }

    return 0;
}

Subhendu Mohapatra

Author & Instructor at plus2net

I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

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