Learn C, C++ Programming

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• strncat( ) function in C language concatenates ( appends ) portion of one string at the end of another string. Syntax for strncat( ) function is given below.

char * strncat ( char * destination, const char * source, size_t num );

• Example :

strncat ( str2, str1, 3 ); – First 3 characters of str1 is concatenated at the end of str2.
strncat ( str1, str2, 3 ); – First 3 characters of str2 is concatenated at the end of str1.

……

• As you know, each string in C is ended up with null character (‘’).
• In strncat( ) operation, null character of destination string is overwritten by source string’s first character and null character is added at the end of new destination string which is created after strncat( ) operation.

Example program for strncat( ) function in C:

• In this program, first 5 characters of the string “cprogramming” is concatenated at the end of the string “C tutorial” using strncat( ) function and result is displayed as “C tutorial fres”.

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

int main( )
{
   char source[ ] = " cprogramming" ;
   char target[ ]= "C tutorial" ;

   printf ( "nSource string = %s", source ) ;
   printf ( "nTarget string = %s", target ) ;

   strncat ( target, source, 5 ) ;

   printf ( "nTarget string after strncat( ) = %s", target ) ;
}

Output:

Other C String functions:

• String.h header file supports all the string functions in C language. All the string functions are given below.
• Click on each string function name below to display example programs.

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