String functions in c language with examples | strcpy, strcat, strcmp, strrev, strlen in C

We need to include string.h header file in a program to use string functions. Different string functions in c language are:

1. strcpy()

strcpy() is one of the most popular String functions in c language . This function is used store a value in a string variable 

Syntax :

strcpy(Str2,Str1);

Str2  is the string variable to store the value.

Str1 is the string value to be stored in string variable Str2.

We can’t use assignment operator = to assign a value to string variable. So we need to use strcpy() function to do that.

char name[20];
strcpy(name,”Amit”);

#include<stdio.h>
#include<string.h>
int main()
{
char name[20];
strcpy(name,”Rahul”);
printf("name=%s",name);
return(0);
}

name=Rahul

2. strcat()

strcat() function is used to combine values of two string variables .

Syntax 

strcat(Str2,Str1);

Str2  is the string variable whose value will be combined with another string value.

Str1 is the string value to be combined with string variable Str2.

#include<stdio.h>
#include<string.h>
int main()
{
char name[30]=”Rahul”;
strcat(name,” Singh”);
printf("name=%s",name);
return(0);
}

name=RahulSingh

Description of above program

In above program, string variable studentname contains value “Amit”. After applying strcat() function, its value will be concatenated with “ Singh” and the final value of string variable studentname would become Amit Singh

3. strlen()

strlen() function is used to count and return number of characters in a string value. 

#include<stdio.h>
#include<string.h>
int main()
{
char name[30]="Rahul";
int num;
num=strlen(name);
printf("\nNumber of characters=%d",num);
return(0);
}

Number of characters=5

Description of above program

In above program, string variable studentname contains value “Amit”. strlen() function finds number of characters in the value “Amit” in string variable studentname that  contains 4 characters. So strlen() would return 4.

 4. strrev()

strrev() function is used to reverse the characters stored in a string value.

#include<stdio.h>
#include<string.h>
int main()
{
char name[20]=”Rahul”;
strrev(name);
printf("name=%s",name);
return(0);
}

Description of above program

In above program, string variable name contains “Rahul”. strrev() reverses the value of name to make it luhaR.

5. strcmp()

strcmp()  function is used to compare two string values. 0 is returned  if the values of strings being compared are same.

#include<stdio.h>
#include<string.h>
int main()
{
char name[35];
strcpy(name,”Sumit”);
if(strcmp(studentname,”Amit”)==0)
  cout<<”\nWelcome Amit”;
else
  cout<<”Wrong User”;
return(0);
}

Description of above program

In this program, string variable name contains “Sumit”. String variable name has been compared with the string value Amit. Value of name i.e. sumit doesn’t match Amit so the output would be wrong user.

6. strcmpi()

strcmpi()  function is used to compare string values but capital letters and small letters are considered same.

#include<stdio.h>
#include<string.h>
int main()
{
char n1[30],n2[30];
printf("Enter a string value=");
gets(n1);
printf("Enter another string value=");
gets(2);
if(strcmpi(n1,n2)==0)
printf("Same");
else
printf("Not same");
return(0);
}

Description of above program

In this program, string variable n1 contains value “Aman” and n2  contains “AMAN”. n1 and n2 contain same values with different cases. They are considered same so message “Same”  gets displayed .

7. strlwr()

strlwr() function converts the uppercase letters to lowercase letters in a string value.

#include<stdio.h>
#include<string.h>
int main()
{
char sname[30]=”SUMIT”;
strlwr(sname);
printf("\nsname=%s",sname);
return(0);
}

sname=sumit

Description of above program

In this program, string variable sname contains “Sumit”.  strlwr() function converts the value into small case i.e. sumit.

8. strupr()

strupr() function converts the small case letters to capital letters in a string value.

Description of above program

In this program, string variable sname contains “sumit”. strupr() function converts the value into capital case i.e. “SUMIT”.

Write C program for following:

1. Program to read a name. If the name is “Raman”, message “Hi” should be displayed otherwise “Bye” should be displayed.
2. Program to read name and password of a user. If name is “Ramesh” and password is “Sharma”. Multiplication of two numbers should be displayed otherwise division of those numbers should be displayed.