.\" Copyright, the authors of the Linux man-pages project
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.TH strlcpy 3 2026-07-11 "Linux man-pages 6.19"
.SH NAME
strlcpy, strlcat
\-
string return-hypothetical-non-truncated-length copy/catenate (with truncation)
.SH LIBRARY
Standard C library
.RI ( libc ,\~ \-lc )
.SH SYNOPSIS
.nf
.B #include <string.h>
.P
.BR size_t\~strlcpy( size_t\~dsize;
.BI "               char\~" dst [restrict\~ dsize "], const\~char\~*restrict\~" src ,
.BI "               size_t\~" dsize );
.BR size_t\~strlcat( size_t\~dsize;
.BI "               char\~" dst [restrict\~ dsize "], const\~char\~*restrict\~" src ,
.BI "               size_t\~" dsize );
.fi
.SH DESCRIPTION
.BR strlcpy ()
copies the string pointed to by
.IR src ,
into a string at the buffer pointed to by
.IR dst .
.P
.BR strlcat ()
catenates the string pointed to by
.IR src ,
after the string pointed to by
.I dst
(overwriting its terminating null byte).
.P
For both functions,
if the string doesn't fit in the buffer,
it is truncated.
.SH RETURN VALUE
These functions return the total length of the string they tried to create,
as if truncation didn't happen.
.SH STANDARDS
POSIX.1-2024.
.SH HISTORY
OpenBSD 2.4, POSIX.1-2024, glibc 2.38.
.SH BUGS
These functions are vulnerable to denial of service (DoS) attacks,
since they read the entire source string.
.P
.BR strscpy (9)
is a better function for copying with truncation,
as it doesn't have that issue.
It's not provided by libc,
so users should write their own implementation.
.SH SEE ALSO
.BR strlcpy (3),
.BR strcpy (3),
.BR string (3)