String in C

• C Strings are nothing but array of characters ended with null character (‘\0’).
• This null character indicates the end of the string.
• Strings are always enclosed by double quotes. Whereas, character is enclosed by single quotes in C.

Example for C string: 

• char string[20] = { ‘d’ , ’i’ , ‘v’ , ‘a’ , ‘s’ , ‘n’ , ‘i’ , ‘k’ , ‘h’ , ’r’ , ‘a’  , ‘\0’}; (or)
• char string[20] = “divasnikhra”; (or)
• char string []    = “divasnikhra”;
• Difference between above declarations are, when we declare char as “string[20]“, 20 bytes of memory space is allocated for holding the string value.
• When we declare char as “string[]“, memory space will be allocated as per the requirement during execution of the program.

Example program for C string:

#include <stdio.h>
#include<conio.h>
void main ()
{
   char string[20] = "divasnikhra";
   printf("The string is :  %s \n", string );
   getch();
}

Output:

The string is :     divasnikhra

C String functions:

string.h header file supports all the string functions in C language. All the string functions are given below. Click on each function name to display an example program.

1 strcat(str1, str2)  Concatenates str2 at the end of str1.

2 strcpy(str1, str2)  Copies str2 into str1

3 strlen(strl)  gives the length of str1.

4 strcmp(str1, str2)  Returns 0 if str1 is same as str2. Returns <0 if strl < str2. Returns >0 if str1 > str2.

5 strchr(str1, char)  Returns pointer to first occurrence of char in str1.

6 strstr(str1, str2)  Returns pointer to first occurrence of str2 in str1.

7 strcmpi(str1,str2)  Same as strcmp() function. But, this function negotiates case.  “A” and “a” are treated as same.

8 strdup()  duplicates the string

9 strlwr()  converts string to lowercase

10 strncat()  appends a portion of string to another

11 strncpy()  copies given number of characters of one string to another

12 strrchr()  last occurrence of given character in a string is found

13 strrev()  reverses the given string

14 strset()  sets all character in a string to given character

15 strupr()  converts string to uppercase

16 strtok()  tokenizing given string using delimiter

Example program for strlen:

It counts number of characters available in a string.

#include <stdio.h>
#include <string.h>
#include<conio.h>
void main( )
{
    int len1, len2 ;
    char array1[50]="virtualctutorials.blogspot.com" ;
    char array2[50]="Divasnikhra " \
                    "Avantika";
    len1 = strlen(array1) ;
    len2 = strlen(array2) ;
    printf ( "\nFirst string length  = %d \n" , len1 ) ;
    printf ( "\nSecond string length  = %d \n" , len2 ) ;
    getch();
}

Output:

First string length = 30

Second string length = 19

Example program for strcpy:

It copies contents of one string to another

#include <stdio.h>
#include <string.h>
#include<conio.h>
void main( )
{
   char source[ ] = "virtualctutorials.blogspot.com" ;
   char target[50] ;
   strcpy ( target, source ) ;
   printf ( "\nContetnt of source string = %s", source ) ;
   printf ( "\nContetnt of target string = %s", target ) ;
   getch();
}

Output:

Contetnt of source string = virtualctutorials.blogspot.com

Contetnt of target string = virtualctutorials.blogspot.com

Example program for strcat:

It concatenates two given strings.

#include <stdio.h>
#include <string.h>
#include<conio.h>
void main( )
{
   char source[ ] = " Divas" ;
   char target[20]= " C Tutorial" ;
   strcat ( target, source ) ;
   printf ( "\nContent of source string = %s", source ) ;
   printf ( "\nContetnt of target string = %s", target ) ;
   getch();
}

Output:

Contetnt of source string = Divas

Contetnt of target string = C Tutorial Divas

Example program for strcmp:

It compares two strings and returns 0 if they are same. If string1< string2, it returns < 0 value. If string1> string2, it returns > 0 value.

#include <stdio.h>
#include <string.h>
#include<conio.h>
void main( )
{
   char str1[ ] = "fresh" ;
   char str2[ ] = "refresh" ;
   int i, j, k ;
   i = strcmp ( str1, "fresh" ) ;
   j = strcmp ( str1, str2 ) ;
   k = strcmp ( str1, "f" ) ;
   printf ( "\n%d %d %d", i, j, k ) ;
   getch();
}

Output:

0 -1 1

Example program for strchr:

It returns pointer to the first occurrence of character in given string.

#include <stdio.h>
#include <string.h>
#include <conio.h>
void main ()
{
   char string[55] ="This is a string for testing";
   char *p;
   p = strchr (string,'i');
   while (p!=NULL)
   {
      printf ("Character i found at %d\n",p-string+1);
      p=strchr(p+1,'i');
   }
   getch();
}

Output:

Character i found at 3Character i found at 6Character i found at 14Character i found at 26

Example program for strstr:

It returns pointer to the first occurrence of string 2 in given string1.

#include <stdio.h>
#include <string.h>
#include <conio.h>
void main ()
{
   char string[55] ="This is a string for testing";
   char *p;
   p = strstr (string,"for");
   if (p)
   {
      printf("string found\n" );
   }
   else
      printf("string not found");
   getch();
}

Output:

string found

Example program for strrchr:

It finds the last occurrence of given character in a string.

#include <stdio.h>
#include <string.h>
#include <conio.h>
void main ()
{
  char string[50] = "This is a string for testing";
  char *p;
  p = strrchr(string,'t');
  printf ("The position of last occurrence of 't' is found " \
          "at %d \n",p-string+1);
  getch();
}

Output:

The position of last occurrence of ‘t’ is found at 25

Example program for strset:

It sets all the characters in a string to given character.

#include<stdio.h>
#include<string.h>
#include<conio.h>
void main()
{
   char str[20] = "Test String";
   printf("Original string is : %s", str);
   printf("Test string after string set : %s",strset(str,'#'));
   printf("After string set: %s",str);
   getch();
}

Output:

Original string is :      Test String

Test string after string set : ###########

Example program for strnset:

It sets the portion of characters in a string to given character.

#include<stdio.h>
#include<string.h>
#include<conio.h>
void main()
{
    char str[20] = "Test String";
    printf("Original string is : %s", str);
    printf("Test string after string n set" \
           " : %s", strnset(str,'#',4));
    printf("After string n set : %s", str);
    getch();
}

Output:

Original string is :      Test String

Test string after string set : #### String

Example program for strupr:

It converts string to uppercase.

#include<stdio.h>
#include<string.h>
#include<conio.h>
void main()
{
    char str[] = "Modify This String To Upper";
    printf("%s\n",strupr(str));
    getch();
}

Output:

MODIFY THIS STRING TO UPPER

Example program for strlwr:

It converts string to lowercase.

#include<stdio.h>
#include<string.h>
#include<conio.h>
void main()
{
    char str[] = "MODIFY This String To LOwer";
    printf("%s\n",strlwr (str));
    getch();
}

Output:

modify this string to lower

Example program for strncat:

It appends a portion of string to another string.

#include <stdio.h>
#include<conio.h>
#include <string.h>
void main ()
{
   char s1[30];
   char s2[20];
   strcpy (s1,"String1 ");
   strcpy (s2,"String2 ");
   strncat (s1, s2, 3);
   printf("Result : %s", s1);
   getch();
}

Output:

Result : String1 Str

Example program for strcpy and strncpy:

It copies given number of characters of one string to another.

#include <stdio.h>
#include<conio.h>
#include <string.h>
void main ()
{
  char s1[30];
  char s2[20];
  strcpy (s2,"String2 ");
  strncpy (s1, s2, 4);
  printf("Result : %s", s1);
  getch();
}

Output:

Result : Stri

Example program for strtok:

It tokenizes the given string using delimiter. That means, It parses a given string using delimiter.

#include <stdio.h>
#include<conio.h>
#include <string.h>
void main ()
{
  char string[50] ="Test,string1,Test,string2:Test:string3";
  char *p;
  printf ("string  \"%s\" is split into tokens:\n",string);
  p = strtok (string,",:");
  while (p!= NULL)
  {
    printf ("%s\n",p);
    p = strtok (NULL, ",:");
  }
  getch();
}

Output:

string “Test,string1,Test,string2:Test:string3″ is split into tokens:Teststring1Teststring2Teststring3

Example program for strdup:

It duplicates the given string.

#include <stdio.h>
#include<conio.h>
#include <string.h>
void main()
{
    char *p1 = "Raja";
    char *p2;
    p2 = strdup(p1);
    printf("Duplicated string is : %s", p2);
    getch();
}

Output:

Duplicated string is : Raja

Example program for strrev:

It reverses the given string.

#include<stdio.h>
#include<conio.h>
#include<string.h>
void main()
{
   char name[30] = "string";
   printf("Enter your name to reverse\n");
   strrev(name);
   printf("Reversed name is : \n%s\n",name);
   getch();
}

 Output:

gnirts