C - strcpy() function

C strcpy() function - copy a string and return a pointer to the end of the result

The strcpy() function is used to copy string2, including the ending null character, to the location that is specified by string1.

Why and when to use strcpy()

• String Copying: strcpy() is used to copy one string into another.
• Overwriting Content: It can replace the contents of a destination string with the source string.
• Initial String Setup: Often used to initialize strings with specific content.
• Avoiding Modifications to Original String: Helps maintain a copy of the original string for comparison or manipulation without altering it.

Syntax:

char *strcpy(char *string1, const char *string2)

Parameters:

Return value from strcpy()

Returns the destination string. No return value is reserved to indicate an error.

Examples: strcpy() function

Example 1: How strcpy() copies the contents of string2 to string1

This example demonstrates how strcpy() copies the contents of string2 to string1. Initially, both string1 and string2 contain "String1" and "String2" respectively. After strcpy(string1, string2), string1 now matches string2, both containing "String2". This illustrates how strcpy() overwrites the contents of the destination string.

Code:

#include <stdio.h>
#include <string.h>
 
#define SIZE 40
 
int main(void)
{
  char string1[SIZE] = "String1";
  char string2[SIZE] = "String2";
  char * return_string;
  printf("Before applying strcpy() function:"); 
  printf("\nstring1 = %s",string1);
  printf("\nstring2 = %s",string2);
  printf("\n\nAfter applying strcpy() function -> strcpy(string1, string2):"); 
  strcpy(string1, string2);
  printf("\nstring1 = %s",string1);
  printf("\nstring2 = %s",string2);
} 

Output:

Before applying strcpy() function:
string1 = String1
string2 = String2

After applying strcpy() function -> strcpy(string1, string2):
string1 = String2
string2 = String2

Example 2: Copying a String to Initialize a Greeting

Code:

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

int main() {
    // Define the greeting template
    char greeting[50] = "Hello, ";
    // Define a name to add to the greeting
    char name[] = "Gamil";

    // Copy the name into the greeting after "Hello, "
    strcpy(greeting + 7, name);

    // Print the complete greeting
    printf("Full Greeting: %s\n", greeting);
    return 0;
}

Output:

Full Greeting: Hello, Gamil

Explanation:

• Initializes the greeting with "Hello, ".
• Copies name into greeting at position 7, adding it after "Hello, ".
• Outputs the complete greeting, resulting in "Hello, Gamil ".

Example 3: Using strcpy() to swap string values using a temporary buffer

Code:

#include <stdio.h>
#include <string.h>
int main() {
    // Define two strings
    char str1[20] = "Apple";
    char str2[20] = "Orange";
    char temp[20]; // Temporary storage

    // Print original values
    printf("Before swap:\nstr1 = %s\nstr2 = %s\n", str1, str2);

    // Copy str1 to temp
    strcpy(temp, str1);
    // Copy str2 to str1
    strcpy(str1, str2);
    // Copy temp (original str1) to str2
    strcpy(str2, temp);

    // Print swapped values
    printf("After swap:\nstr1 = %s\nstr2 = %s\n", str1, str2);
    return 0;
}

Output:

Before swap:
str1 = Apple
str2 = Orange
After swap:
str1 = Orange
str2 = Apple

Explanation:

• Defines str1 and str2, containing "Apple" and "Orange".
• Copies str1 into temp, then str2 into str1.
• Copies temp into str2, completing the swap.
• Displays the swapped results.

C Programming Code Editor:

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