String Library functions
The predefined functions which are designed to handle strings are available in the library “string.h”. They are −
- strlen ()
- strcmp ()
- strcpy ()
- strncmp ()
- strncpy ()
- strrev ()
- strcat ()
- strstr ()
- strncat ()
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