How to Copy String in C: Syntax and Examples

In C, you copy a string using the strcpy function from string.h. It copies the content of one string into another, including the ending null character.

Syntax

The strcpy function copies the source string into the destination string, including the null terminator.

• dest: A character array where the string will be copied.
• src: The source string to copy from.

c

char *strcpy(char *dest, const char *src);

Example

This example shows how to copy one string into another using strcpy and then print the copied string.

c

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

int main() {
    char source[] = "Hello, friend!";
    char destination[50];

    strcpy(destination, source);

    printf("Copied string: %s\n", destination);
    return 0;
}

Output

Copied string: Hello, friend!

Common Pitfalls

Common mistakes when copying strings in C include:

• Not allocating enough space in the destination array, which can cause buffer overflow.
• Forgetting to include string.h to use strcpy.
• Using strcpy with overlapping source and destination strings, which is unsafe.

Always ensure the destination array is large enough to hold the source string plus the null terminator.

c

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

int main() {
    char source[] = "Hello, friend!";
    char destination[5]; // Too small!

    // Unsafe: may cause buffer overflow
    // strcpy(destination, source);

    // Safe way: use strncpy to limit copy size
    strncpy(destination, source, sizeof(destination) - 1);
    destination[sizeof(destination) - 1] = '\0'; // Ensure null termination

    printf("Copied string safely: %s\n", destination);
    return 0;
}

Output

Copied string safely: Hell

Quick Reference

Function	Description	Notes
strcpy(dest, src)	Copies entire src string to dest	Dest must be large enough
strncpy(dest, src, n)	Copies up to n characters	May not null-terminate if src longer than n
memcpy(dest, src, n)	Copies n bytes (not string safe)	Use only if you know exact size

Key Takeaways

Use strcpy to copy strings safely when destination has enough space.

Always include string.h to use string functions like strcpy.

Avoid buffer overflow by ensuring destination array size is sufficient.

Use strncpy if you want to limit the number of characters copied.

Never use strcpy with overlapping source and destination strings.