'\" t
.\" Copyright, the authors of the Linux man-pages project
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.TH strcpy 3 2026-02-25 "Linux man-pages 6.18"
.SH NAME
strcpy, strcat \- copy or catenate a string
.SH LIBRARY
Standard C library
.RI ( libc ,\~ \-lc )
.SH SYNOPSIS
.nf
.B #include <string.h>
.P
.BI "char *strcpy(char *restrict " dst ", const char *restrict " src );
.BI "char *strcat(char *restrict " dst ", const char *restrict " src );
.fi
.SH DESCRIPTION
.TP
.BR strcpy ()
This function copies the string pointed to by
.IR src ,
into a string
at the buffer pointed to by
.IR dst .
The programmer is responsible for allocating a destination buffer large enough,
that is,
.IR "strlen(src) + 1" .
.IP
It is equivalent to
.IP
.in +4n
.EX
stpcpy(dst, src), dst
.EE
.in
.TP
.BR strcat ()
This function catenates the string pointed to by
.IR src ,
after the string pointed to by
.I dst
(overwriting its terminating null byte).
The programmer is responsible for allocating a destination buffer large enough,
that is,
.IR "strlen(dst) + strlen(src) + 1" .
.IP
It is equivalent to
.IP
.in +4n
.EX
stpcpy(strnul(dst), src), dst
.EE
.in
.SH RETURN VALUE
These functions return
.IR dst .
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lbx lb lb
l l l.
Interface	Attribute	Value
T{
.na
.nh
.BR strcpy (),
.BR strcat ()
T}	Thread safety	MT-Safe
.TE
.SH STANDARDS
C11, POSIX.1-2008.
.SH HISTORY
POSIX.1-2001, C89, SVr4, 4.3BSD.
.SH CAVEATS
The strings
.I src
and
.I dst
may not overlap.
.P
If the destination buffer is not large enough,
the behavior is undefined.
See
.B _FORTIFY_SOURCE
in
.BR feature_test_macros (7).
.P
.BR strcat ()
can be very inefficient.
Read about
.UR https:\://www.joelonsoftware.com/\:2001/12/11/\:back\-to\-basics/
Shlemiel the painter
.UE .
.SH EXAMPLES
.\" SRC BEGIN (strcpy.c)
.EX
#include <err.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
\&
int
main(void)
{
    char    *buf1;
    size_t  len, size;
\&
    size = strlen("Hello ") + strlen("world") + strlen("!") + 1;
    buf1 = malloc(sizeof(*buf1) * size);
    if (buf1 == NULL)
        err(EXIT_FAILURE, "malloc()");
\&
    strcpy(buf1, "Hello ");
    strcat(buf1, "world");
    strcat(buf1, "!");
    len = strlen(buf1);
\&
    printf("[len = %zu]: ", len);
    puts(buf1);  // "Hello world!"
    free(buf1);
\&
    exit(EXIT_SUCCESS);
}
.EE
.\" SRC END
.SH SEE ALSO
.BR stpcpy (3),
.BR strdup (3),
.BR string (3),
.BR wcscpy (3),
.BR string_copying (7)