C strcat() function

C strcat() function - concatenate two strings

The strcat() function concatenates string2 to string1 and ends the resulting string with the null character.

Use strcat() when:

• Concatenating strings in cases where you need to build sentences or combine multiple strings.
• Appending suffixes or additional information to an existing string.
• Building formatted output strings by gradually adding content to a base string.

Syntax:

char *strcat(char *string1, const char *string2);

Parameters:

Return value from strcat()

The strcat() function shall return string1. No return value is reserved to indicate an error.

Examples: strcat() function

Example 1: Combine strings

The existing example uses strcat() to append " Programming" to the end of string1, which initially contains "C". The result is "C Programming", showcasing how strcat() can combine strings to form a larger phrase.

Code:

#include <stdio.h>
#include <string.h> 
#define SIZE 40 
int main(void)
{
  char string1[SIZE] = "C";
  char * ptr;
 
  ptr = strcat( string1, " Programming" );
  printf( "string1 = %s\n", string1 );
 
}

Output:

string1 = C Programming

Example 2: Concatenating multiple strings

This example demonstrates using strcat() to join multiple words into a sentence.

Code:

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

int main() {
    // Define an empty buffer with enough space to hold the final sentence
    char sentence[50] = "Hello,";

    // Append each word to the sentence
    strcat(sentence, " world");
    strcat(sentence, " of");
    strcat(sentence, " C programming!");

    // Display the concatenated sentence
    printf("Concatenated Sentence: %s\n", sentence);

    return 0;
}

Output:

Concatenated Sentence: Hello, world of C programming!

Explanation:

• A buffer sentence is initialized with the word "Hello,".
• Each subsequent word is appended to sentence using strcat().
• The final sentence, "Hello, world of C programming!" is printed, demonstrating strcat()'s capability to create complete sentences from multiple parts.

Example 3: Creating a full path from directory and file names

This example demonstrates using strcat() to form a file path by combining a directory name and a file name.

Code:

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

int main() {
    // Define a directory path and a file name
    char path[100] = "/home/user/documents";
    char filename[] = "/file.txt";

    // Append the file name to the directory path
    strcat(path, filename);

    // Display the complete path
    printf("Complete Path: %s\n", path);

    return 0;
}

Output:

Complete Path: /home/user/documents/file.txt

Explanation:

• The path string holds a directory location.
• filename stores the file name to be added to the directory.
• strcat() appends filename to path, forming the complete file path "/home/user/documents/file.txt", which is then printed.

C Programming Code Editor:

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