C String Functions

There are many important string functions defined in “string.h” library.

No.	Function	Description
1)	strlen(string_name)	returns the length of string name.
2)	strcpy(destination, source)	copies the contents of source string to destination string.
3)	strcat(first_string, second_string)	concats or joins first string with second string. The result of the string is stored in first string.
4)	strcmp(first_string, second_string)	compares the first string with second string. If both strings are same, it returns 0.
5)	strrev(string)	returns reverse string.
6)	strlwr(string)	returns string characters in lowercase.
7)	strupr(string)	returns string characters in uppercase.

C String Length: strlen() function

The strlen() function returns the length of the given string. It doesn’t count null character ‘\0’.

#include<stdio.h>

#include <string.h>

int main(){

char ch[20]={‘j’, ‘a’, ‘v’, ‘a’, ‘t’, ‘p’, ‘o’, ‘i’, ‘n’, ‘t’, ‘\0’};

printf(“Length of string is: %d”,strlen(ch));

return 0;

}

Output:

Length of string is: 10

C Copy String: strcpy()

The strcpy(destination, source) function copies the source string in destination.

#include<stdio.h>

#include <string.h>

int main(){

char ch[20]={‘j’, ‘a’, ‘v’, ‘a’, ‘t’, ‘p’, ‘o’, ‘i’, ‘n’, ‘t’, ‘\0’};

char ch2[20];

strcpy(ch2,ch);

printf(“Value of second string is: %s”,ch2);

return 0;

}

Output:

Value of second string is: cloudandclear

C String Concatenation: strcat()

The strcat(first_string, second_string) function concatenates two strings and result is returned to first_string.

#include<stdio.h>

#include <string.h>

int main(){

char ch[10]={‘h’, ‘e’, ‘l’, ‘l’, ‘o’, ‘\0’};

char ch2[10]={‘c’, ‘\0’};

strcat(ch,ch2);

printf(“Value of first string is: %s”,ch);

return 0;

}

Output:

Value of first string is: helloc

C Compare String: strcmp()

The strcmp(first_string, second_string) function compares two string and returns 0 if both strings are equal.

Here, we are using gets() function which reads string from the console.

#include<stdio.h>

#include <string.h>

int main(){

char str1[20],str2[20];

printf(“Enter 1st string: “);

gets(str1);//reads string from console

printf(“Enter 2nd string: “);

gets(str2);

if(strcmp(str1,str2)==0)

printf(“Strings are equal”);

else

printf(“Strings are not equal”);

return 0;

}

Output:

Enter 1st string: hello

Enter 2nd string: hello

Strings are equal

C Reverse String: strrev()

The strrev(string) function returns reverse of the given string. Let’s see a simple example of strrev() function.

#include<stdio.h>

#include <string.h>

int main(){

char str[20];

printf(“Enter string: “);

gets(str);//reads string from console

printf(“String is: %s”,str);

printf(“\nReverse String is: %s”,strrev(str));

return 0;

}

Output:

Enter string: cloudandclear

String is: cloudandclear

Reverse String is: tnioptavaj

C String Lowercase: strlwr()

The strlwr(string) function returns string characters in lowercase. Let’s see a simple example of strlwr() function.

#include<stdio.h>

#include <string.h>

int main(){

char str[20];

printf(“Enter string: “);

gets(str);//reads string from console

printf(“String is: %s”,str);

printf(“\nLower String is: %s”,strlwr(str));

return 0;

}

Output:

Enter string: cloudandclear

String is: cloudandclear

Lower String is: cloudandclear

C String Uppercase: strupr()

The strupr(string) function returns string characters in uppercase. Let’s see a simple example of strupr() function.

#include<stdio.h>

#include <string.h>

int main(){

char str[20];

printf(“Enter string: “);

gets(str);//reads string from console

printf(“String is: %s”,str);

printf(“\nUpper String is: %s”,strupr(str));

return 0;

}

Output:

Enter string: cloudandclear

String is: cloudandclear

Upper String is: CLOUDANDCLEAR

C String strstr()

The strstr() function returns pointer to the first occurrence of the matched string in the given string. It is used to return substring from first match till the last character.

Syntax:

char *strstr(const char *string, const char *match)

String strstr() parameters

string: It represents the full string from where substring will be searched.

match: It represents the substring to be searched in the full string.

String strstr() example

#include<stdio.h>

#include <string.h>

int main(){

char str[100]=”this is cloudandclear with c and java”;

char *sub;

sub=strstr(str,”java”);