strstr - cppreference.com (original) (raw)

Defined in header <string.h>
char* strstr( const char* str, const char* substr ); (1)
/*QChar*/* strstr( /*QChar*/* str, const char* substr ); (2) (since C23)

  1. Finds the first occurrence of the null-terminated byte string pointed to by substr in the null-terminated byte string pointed to by str. The terminating null characters are not compared.

  2. Type-generic function equivalent to (1). Let T be an unqualified character object type.

If a macro definition of each of these generic functions is suppressed to access an actual function (e.g. if (strstr) or a function pointer is used), the actual function declaration (1) becomes visible.

The behavior is undefined if either str or substr is not a pointer to a null-terminated byte string.

[edit] Parameters

str - pointer to the null-terminated byte string to examine
substr - pointer to the null-terminated byte string to search for

[edit] Return value

Pointer to the first character of the found substring in str, or a null pointer if such substring is not found. If substr points to an empty string, str is returned.

[edit] Example

#include <stdio.h> #include <string.h>   void find_str(char const* str, char const* substr) { char const* pos = strstr(str, substr); if (pos) printf( "Found the string [%s] in [%s] at position %td\n", substr, str, pos - str ); else printf( "The string [%s] was not found in [%s]\n", substr, str ); }   int main(void) { char const* str = "one two three"; find_str(str, "two"); find_str(str, ""); find_str(str, "nine"); find_str(str, "n");   return 0; }

Output:

Found the string [two] in [one two three] at position 4 Found the string [] in [one two three] at position 0 The string [nine] was not found in [one two three] Found the string [n] in [one two three] at position 1

[edit] References

[edit] See also