C – strcat() function

• strcat( ) function in C language concatenates two given strings. It concatenates source string at the end of destination string. Syntax for strcat( ) function is given below.

char * strcat ( char * destination, const char * source );

• Example :

strcat ( str2, str1 ); - str1 is concatenated at the end of str2.
strcat ( str1, str2 ); - str2 is concatenated at the end of str1.

• As you know, each string in C is ended up with null character (‘\0′).
• In strcat( ) 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 strcat( ) operation.

Example program for strcat( ) function in C:

• In this program, two strings “computerscience” and “C tutorial” are concatenated using strcat( ) function and result is displayed as “C tutorial computerscience”.

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

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

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

   strcat ( target, source ) ;

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

Output:

Source string                       = computerscience Target string                        = C tutorial Target string after strcat( ) = C tutorial computerscience

Other C String functions:

• String.h header file supports all the string functions in C language. All the string functions are given below.

S.no	String functions	Description
1	strcat ( )	Concatenates str2 at the end of str1.
2	strncat ( )	appends a portion of string to another
3	strcpy ( )	Copies str2 into str1
4	strncpy ( )	copies given number of characters of one string to another
5	strlen ( )	gives the length of str1.
6	strcmp ( )	Returns 0 if str1 is same as str2. Returns <0 if strl < str2. Returns >0 if str1 > str2.
7	strcmpi ( )	Same as strcmp() function. But, this function negotiates case.  “A” and “a” are treated as same.
8	strchr ( )	Returns pointer to first occurrence of char in str1.
9	strrchr ( )	last occurrence of given character in a string is found
10	strstr ( )	Returns pointer to first occurrence of str2 in str1.
11	strrstr ( )	Returns pointer to last occurrence of str2 in str1.
12	strdup ( )	duplicates the string
13	strlwr ( )	converts string to lowercase
14	strupr ( )	converts string to uppercase
15	strrev ( )	reverses the given string
16	strset ( )	sets all character in a string to given character
17	strnset ( )	It sets the portion of characters in a string to given character
18	strtok ( )	tokenizing given string using delimiter