NAME

strncat — concatenate a string with part of another

SYNOPSIS

#include <string.h>

char *strncat(char *restrict s1, const char *restrict s2, size_t n);


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 strncat() function shall append not more than n bytes (a NUL character and bytes that follow it are not appended) from the array pointed to by s2 to the end of the string pointed to by s1. The initial byte of s2 overwrites the NUL character at the end of s1. A terminating NUL character is always appended to the result. If copying takes place between objects that overlap, the behavior is undefined.

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

RETURN VALUE

The strncat() function shall return s1; no return value shall be reserved to indicate an error.

ERRORS

No errors are defined.

EXAMPLES

None.

APPLICATION USAGE

None.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

strcat, strlcat

XBD <string.h>

CHANGE HISTORY

First released in Issue 1. Derived from Issue 1 of the SVID.

Issue 6

The strncat() prototype is updated for alignment with the ISO/IEC 9899:1999 standard.

Issue 8

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

Austin Group Defect 986 is applied, adding strlcat() to the SEE ALSO section.