.\" Copyright (c) 1990, 1991, 1993
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.\" This code is derived from software contributed to Berkeley by
.\" Chris Torek and the American National Standards Committee X3,
.\" on Information Processing Systems.
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.\"     from: @(#)strcpy.3	8.1 (Berkeley) 6/4/93
.\"	$NetBSD: strcpy.3,v 1.23.26.1 2024/09/20 11:22:29 martin Exp $
.\"
.Dd August 11, 2023
.Dt STRCPY 3
.Os
.Sh NAME
.Nm stpcpy ,
.Nm strcpy
.Nd copy strings
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In string.h
.Ft char *
.Fn stpcpy "char * restrict dst" "const char * restrict src"
.Ft char *
.Fn strcpy "char * restrict dst" "const char * restrict src"
.Sh DESCRIPTION
The
.Fn stpcpy
and
.Fn strcpy
functions
copy the string
.Fa src
to
.Fa dst ,
including the terminating
.Tn NUL
byte.
.Pp
The strings
.Fa src
and
.Fa dst
may not overlap.
The string
.Fa src
must be terminated by a
.Tn NUL
byte.
The memory for
.Fa dst
must have space for
.Fn strlen src Li "+ 1"
bytes.
.Sh RETURN VALUES
The
.Fn strcpy
function returns
.Fa dst .
.Pp
The
.Fn stpcpy
function returns a pointer to the terminating
.Tn NUL
byte of
.Fa dst .
.Sh SEE ALSO
.Xr bcopy 3 ,
.Xr memccpy 3 ,
.Xr memcpy 3 ,
.Xr memmove 3 ,
.Xr strlcpy 3 ,
.Xr strncpy 3 ,
.Xr wcscpy 3
.Sh STANDARDS
The
.Fn strcpy
function conforms to
.St -isoC-99 .
.Pp
The
.Fn stpcpy
function conforms to
.St -p1003.1-2008 .
.Sh HISTORY
The
.Fn stpcpy
function first appeared in
.Nx 6.0 .
.Sh SECURITY CONSIDERATIONS
The
.Fn strcpy
and
.Fn stpcpy
functions copy until a
.Tn NUL
terminator without any bounds checks on the size of the input or output
buffers.
If the input buffer is missing a
.Tn NUL
terminator, or the input string is longer than the output buffer, this
can lead to crashes or security vulnerabilities from buffer overruns,
including disclosure of secrets in memory and arbitrary code
execution.
.Pp
The
.Xr strlcpy 3
function is a safer replacement for
.Fn strcpy
which allows the caller to specify the space allocated for
.Fa dst .
.Xr strlcpy 3 ,
or
.Xr snprintf 3
with a format string of
.Li \*q%s\*q ,
should be used instead of
.Fn strcpy
and
.Fn stpcpy
wherever possible to avoid buffer overruns in
.Fa dst .
.Po
However, they still require
.Fa src
to be
.Tn NUL Ns -terminated .
.Pc