String Functions in C

This article is about the various string functions available in C programming and the usage of it in our programs.

String functions in C programming

C supports a wide range of functions that manipulates and perform operations on the string. The string handling functions are present in the standard library “string.h” which should be defined in the header file.

strcpy(s1, s2);

The strcpy() function copies string s2 into string s1. Here the size of the destination string should be enough to store the source string.

**char *strcpy(char *destination, const char *source)**

Example

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#include <stdio.h>
   #include <string.h>
    int main() {
      char str1[20] = "programming";
      char str2[20];
      // copying str1 to str2
      strcpy(str2, str1);
      printf("str2: %s\n", str2 );
      return 0;
   }

Output

str2: programming

strcat(s1, s2)

Concatenates string s2 onto the end of string s1. This function simply joins two strings. To use a strcat() function the size of the destination string should be large enough to store the resultant string so as to avoid errors.

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

Example

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#include <stdio.h>
#include <string.h>
int main() {
    char str1[15] = "Hai!";
    char str2[15] = "Hello";
    strcat( str1, str2);
    printf("str1:   %s\n", str1 );
    return 0;
}

Output

str1: Hai!Hello

strlen(s1)

The strlen() function calculates the length of a given string. This function doesn’t count the null character \0 while calculating the length.

ExampleExample

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#include <stdio.h>
#include <string.h>
int main()
{
    char str1[10] = "Program";
    len = strlen(str1);
    printf("Length of string1:  %d\n", len );
    return 0;
}

Output

Length of string1: 7

strcmp(s1, s2)

The strcmp() compares two strings character and returns 0 if s1 and s2 are the same; negative value if s1<s2; positive value if s1>s2.

Example

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#include <stdio.h>
   #include <string.h>
   int main()
   {
       char str1[7] = "xyz",
       char str2[7] = "xYz", 
       char str3[7] = "xyz";
       int result;
   
       // comparing strings str1 and str2
       result = strcmp(str1, str2);
       printf("strcmp(str1, str2) = %d\n", result);
   
       // comparing strings str1 and str3
       result = strcmp(str1, str3);
       printf("strcmp(str1, str3) = %d\n", result);
   
       return 0;
   }

Output

strcmp(str1, str2) = 23
strcmp(str1, str3) = 0

strchr(s1, ch)

Returns a pointer to the first occurrence of character ch in string s1.

Example

    #include <stdio.h>
    #include <string.h>
     int main () {
       const char str[] = "www.google.com";
       const char ch = '.';
       char *ans;
       ans = strchr(str, ch);
       printf("String after |%c| is - |%s|\n", ch, ans);
       return(0);
    }

Output

String after |.| is - |.google.com|

strstr(s1, s2)

Returns a pointer to the first occurrence of string s2 in string s1.

Example

    #include <stdio.h>
    #include <string.h>
    int main() {
       char s1 [] = "My name is preethi";
       printf ("Returned String 1: %s\n", strstr (s1, "name"));
    }

Output

Returned String 1: name is preethi

strlwr()

The strlwr() function converts string to lowercase.

**char strlwr(char str);

Example

 
    #include<stdio.h> 
    #include<string.h> 
    int main() 
    { 
        char str[ ] = "BEAUTIFUL"; 
      
        // converting the given string into lowercase. 
        printf("%s\n",strlwr (str)); 
      
        return  0; 
    } 

Output

beautiful

strupr()

The strupr() function converts string to uppercase.

Example

    #include<stdio.h> 
    #include<string.h> 
    int main() 
    { 
        char str[ ] = "awesome"; 
      
        // converting the given string into uppercase. 
        printf("%s\n",strupr (str)); 
      
        return  0; 
    }

Output

AWESOME