C – strstr() function – Learn C, C++ Programming

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strstr( ) function returns pointer to the first occurrence of the string in a given string. Syntax for strstr( ) function is given below.

char *strstr(const char *str1, const char *str2);

……

Example program for strstr() function in C:

In this program, strstr( ) function is used to locate first occurrence of the string “test” in the string ”This is a test string for testing”. Pointer is returned at first occurrence of the string “test”.

#include <stdio.h>
#include <string.h>
int main ()
{
  char string[55] ="This is a test string for testing";
  char *p;
  p = strstr (string,"test");
  if(p)
  {
    printf("string foundn" );
    printf ("First occurrence of string "test" in "%s" is"
           " "%s"",string, p);
  }
  else printf("string not foundn" );
   return 0;
}

Output:

string found
First occurrence of string “test” in “This is a test string for testing” is “test string for testing”

Other 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 string function name below to display example programs.

S.no	String functions	Description
1	strcat ( )	Concatenates str2 at the end of str1.
2	strncat ( )	appends a portion of string to another
3	strcpy ( )	Copies str2 into str1
4	strncpy ( )	copies given number of characters of one string to another
5	strlen ( )	gives the length of str1.
6	strcmp ( )	Returns 0 if str1 is same as str2. Returns <0 if strl < str2. Returns >0 if str1 > str2.
7	strcmpi ( )	Same as strcmp() function. But, this function negotiates case. “A” and “a” are treated as same.
8	strchr ( )	Returns pointer to first occurrence of char in str1.
9	strrchr ( )	last occurrence of given character in a string is found
10	strstr ( )	Returns pointer to first occurrence of str2 in str1.
11	strrstr ( )	Returns pointer to last occurrence of str2 in str1.
12	strdup ( )	duplicates the string
13	strlwr ( )	converts string to lowercase
14	strupr ( )	converts string to uppercase
15	strrev ( )	reverses the given string
16	strset ( )	sets all character in a string to given character
17	strnset ( )	It sets the portion of characters in a string to given character
18	strtok ( )	tokenizing given string using delimiter