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strstr() function in C:
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”.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | #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 found\n" );     printf ("First occurrence of string \"test\" in \"%s\" is"\            " \"%s\"",string, p);   }   else printf("string not found\n" );    return 0; } | 
Output:
| string found First occurrence of string “test” in “This is a test string for testing” is “test string for testing” | 
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 for detail description and example programs.
| String functions | Description | 
| strcat ( ) | Concatenates str2 at the end of str1 | 
| strncat ( ) | Appends a portion of string to another | 
| strcpy ( ) | Copies str2 into str1 | 
| strncpy ( ) | Copies given number of characters of one string to another | 
| strlen ( ) | Gives the length of str1 | 
| strcmp ( ) | Returns 0 if str1 is same as str2. Returns <0 if strl < str2. Returns >0 if str1 > str2 | 
| strcmpi ( ) | Same as strcmp() function. But, this function negotiates case. “A” and “a” are treated as same. | 
| strchr ( ) | Returns pointer to first occurrence of char in str1 | 
| strrchr ( ) | last occurrence of given character in a string is found | 
| strstr ( ) | Returns pointer to first occurrence of str2 in str1 | 
| strrstr ( ) | Returns pointer to last occurrence of str2 in str1 | 
| strdup ( ) | Duplicates the string | 
| strlwr ( ) | Converts string to lowercase | 
| strupr ( ) | Converts string to uppercase | 
| strrev ( ) | Reverses the given string | 
| strset ( ) | Sets all character in a string to given character | 
| strnset ( ) | It sets the portion of characters in a string to given character | 
| strtok ( ) | Tokenizing given string using delimiter | 
