strcat - Man Page

concatenate two strings


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.


#include <string.h>

char *strcat(char *restrict s1, const char *restrict 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.1-2017 defers to the ISO C standard.

The strcat() function shall append a copy of the string pointed to by s2 (including the terminating NUL character) to the end of the string pointed to by s1. The initial byte of s2 overwrites the NUL character at the end of s1. If copying takes place between objects that overlap, the behavior is undefined.

Return Value

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


No errors are defined.

The following sections are informative.



Application Usage

This version is aligned with the ISO C standard; this does not affect compatibility with XPG3 applications. Reliable error detection by this function was never guaranteed.



Future Directions


See Also


The Base Definitions volume of POSIX.1-2017, <string.h>

Referenced By

localeconv(3p), string.h(0p), strncat(3p).

2017 IEEE/The Open Group POSIX Programmer's Manual