NAME

strstr — find a substring

SYNOPSIS

#include <string.h>

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


DESCRIPTION

^[CX] 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.1-2024 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.

^[CX] The strstr() function shall not change the setting of errno on valid input.

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.

ERRORS

No errors are defined.

EXAMPLES

None.

APPLICATION USAGE

None.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

memmem, strchr

XBD <string.h>

CHANGE HISTORY

First released in Issue 3. Included for alignment with the ANSI C standard.

Issue 8

Austin Group Defect 448 is applied, adding a requirement that strstr() does not change the setting of errno on valid input.

Austin Group Defect 1061 is applied, adding memmem() to the SEE ALSO section.