strstr man page


This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

strstr — find a substring


#include <string.h>

char *strstr(const char *s1, const char *s2);


The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1‐2008 defers to the ISO C standard.

The strstr() function shall locate the first occurrence in the string pointed to by s1 of the sequence of bytes (excluding the terminating NUL character) in the string pointed to by s2.

Return Value

Upon successful completion, strstr() shall return a pointer to the located string or a null pointer if the string is not found.

If s2 points to a string with zero length, the function shall return s1.


No errors are defined.

The following sections are informative.

See Also


The Base Definitions volume of POSIX.1‐2008, <string.h>