Explain string library functions with suitable examples in C

String Library functions

The predefined functions which are designed to handle strings are available in the library string.h. They are −

The strlen () function

It returns the number of characters in a string.

Syntax

int strlen (string name)

Example

#include <string.h>
main (){
   char a[30] = “Hello”;
   int l;
   l = strlen (a);
   printf (“length of the string = %d”, l);
   getch ();
}

Output

length of the string = 5

The strcpy () function

It is for copying source string into destination string.
The length of the destination string >= source string.

Syntax

strcpy (Destination string, Source String);

For example,

1) char a[50];
strcpy (“Hello”,a);
o/p: error
2) char a[50];
strcpy ( a,”hello”);
o/p: a= “Hello”

Example

#include <string.h>
main (){
   char a[50], b[50];
   printf ("enter a source string");
   scanf("%s", a);
   printf("enter destination string");
   scanf("%s",b);
   strcpy ( b,a);
   printf ("copied string = %s",b);
   getch ();
}

Output

Enter a source string : Hello
Copied string = Hello

The strncpy () function

It copy’s ‘n’ characters of source string into destination string.
The length of the destination string must >= that of the source string.

Syntax

strncpy (Destination string, Source String, n);

Example

#include<string.h>
main (){
   char a[50], b[50];
   printf ("enter a string");
   gets (a);
   gets(b);
   strncpy (b,a,3);// copy first 3 char from a string
   b[3] = '\0';
   printf ("copied string = %s",b);
   getch ();
}

Output

Enter a string : Hello
Copied string = Hel
It is also used for extracting substrings;

The strcat () function

It combines two strings.
The length of the destination string must be > than the source string.

Syntax

strcat (Destination String, Source string);

Example

#include <string.h>
main(){
   char a[50] = "Hello";
   char b[20] = "Good Morning";
   clrscr ();
   strcat (a,b);
   printf("concatenated string = %s", a);
   getch ();
}

Output

Concatenated string = Hello Good Morning

The strncat () function

This is used for combining or concatenating n characters of one string into another.
The length of the destination string must be greater than the source string
The resultant concatenated string will be in the destination string.

Syntax

strncat (Destination String, Source string,n);

Example

#include <string.h>
main (){
   char a [30] = "Hello";
   char b [20] = "Good Morning";
   clrscr ();
   strncat (a,b,4);
   a [9] = '\0';
   printf("concatenated string = %s", a);
   getch ();
}

Output

Concatenated string = Hello Good.

The strcmp() function (String comparison)

This function compares 2 strings.
It returns the ASCII difference of the first two non – matching characters in both the strings.

Syntax

int strcmp (string1, string2);
//If the difference is equal to zero, then string1 = string2
//If the difference is positive, then string1 > string2
//If the difference is negative, then string1 < string2

Example

#include<stdio.h>
#include<string.h>
int main (){
   char a[50], b [50];
   int d;
   printf ("Enter 2 strings:");
   scanf ("%s %s", a,b);
   d = strcmp(a,b);
   if (d==0){
      printf("%s is (alphabetically) equal to %s", a,b);
   }else if (d>0){
      printf("%s is (alphabetically) greater than %s",a,b);
   }else if (d<0){
      printf("%s is (alphabetically) less than %s", a,b);
   }
}

Output

Enter 2 strings:apple ball
apple is (alphabetically) less than ball

The strncmp () function

This function is used for comparing first ‘n’ characters of 2 strings.

Syntax

strncmp ( string1, string2,2)

For example, char a[10] = “the”;

char b[10] = “there”

strncmp (a,b,4);

Output − Both strings are equal

The strrev() function

The function is used for reversing a string.
The reversed string will be stored in the same string.

Syntax

strrev (string)

Example

#include<stdio.h>
main (){
   char a[50] ;
   clrscr();
   printf ("enter a string");
   gets (a);
   strrev (a);
   printf("reversed string = %s",a)
   getch ();
}

Output

enter a string Hello
reversed string = olleH

The strstr() function

It is used to search whether a substring is present in the main string or not.
It returns pointer to first occurrence of s2 in s1.

Syntax

strstr(mainsring,substring);

Example

#include<stdio.h>
void main(){
   char a[30],b[30];
   char *found;
   printf("Enter a string:\t");
   gets(a);
   printf("Enter the string to be searched for:\t");
   gets(b);
   found=strstr(a,b);
   if(found)
      printf("%s is found in %s in %d position",b,a,found-a);
   else
      printf("-1 since the string is not found");
   getch();
}

Output

Enter a string: how are you
Enter the string to be searched for: you
you is found in 8 position

Bhanu Priya

Updated on: 14-Sep-2023

29K+ Views

Kickstart Your Career

Get certified by completing the course

Get Started