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'\" t
.\" Copyright 2022 Alejandro Colomar <alx@kernel.org>
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.TH strcpy 3 2024-06-15 "Linux man-pages (unreleased)"
.SH NAME
stpcpy, 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 *stpcpy(char *restrict " dst ", const char *restrict " src );
.BI "char *strcpy(char *restrict " dst ", const char *restrict " src );
.BI "char *strcat(char *restrict " dst ", const char *restrict " src );
.fi
.P
.RS -4
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.RE
.P
.BR stpcpy ():
.nf
Since glibc 2.10:
_POSIX_C_SOURCE >= 200809L
Before glibc 2.10:
_GNU_SOURCE
.fi
.SH DESCRIPTION
.TP
.BR stpcpy ()
.TQ
.BR strcpy ()
These functions copy 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" .
For the difference between the two functions, see RETURN VALUE.
.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" .
.P
An implementation of these functions might be:
.P
.in +4n
.EX
char *
stpcpy(char *restrict dst, const char *restrict src)
{
char *p;
\&
p = mempcpy(dst, src, strlen(src));
*p = \[aq]\[rs]0\[aq];
\&
return p;
}
\&
char *
strcpy(char *restrict dst, const char *restrict src)
{
stpcpy(dst, src);
return dst;
}
\&
char *
strcat(char *restrict dst, const char *restrict src)
{
stpcpy(dst + strlen(dst), src);
return dst;
}
.EE
.in
.SH RETURN VALUE
.TP
.BR stpcpy ()
This function returns
a pointer to the terminating null byte of the copied string.
.TP
.BR strcpy ()
.TQ
.BR strcat ()
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 stpcpy (),
.BR strcpy (),
.BR strcat ()
T} Thread safety MT-Safe
.TE
.SH STANDARDS
.TP
.BR stpcpy ()
POSIX.1-2008.
.TP
.BR strcpy ()
.TQ
.BR strcat ()
C11, POSIX.1-2008.
.SH STANDARDS
.TP
.BR stpcpy ()
POSIX.1-2008.
.TP
.BR strcpy ()
.TQ
.BR strcat ()
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 *p;
char *buf1;
char *buf2;
size_t len, maxsize;
\&
maxsize = strlen("Hello ") + strlen("world") + strlen("!") + 1;
buf1 = malloc(sizeof(*buf1) * maxsize);
if (buf1 == NULL)
err(EXIT_FAILURE, "malloc()");
buf2 = malloc(sizeof(*buf2) * maxsize);
if (buf2 == NULL)
err(EXIT_FAILURE, "malloc()");
\&
p = buf1;
p = stpcpy(p, "Hello ");
p = stpcpy(p, "world");
p = stpcpy(p, "!");
len = p \- buf1;
\&
printf("[len = %zu]: ", len);
puts(buf1); // "Hello world!"
free(buf1);
\&
strcpy(buf2, "Hello ");
strcat(buf2, "world");
strcat(buf2, "!");
len = strlen(buf2);
\&
printf("[len = %zu]: ", len);
puts(buf2); // "Hello world!"
free(buf2);
\&
exit(EXIT_SUCCESS);
}
.EE
.\" SRC END
.SH SEE ALSO
.BR strdup (3),
.BR string (3),
.BR wcscpy (3),
.BR string_copying (7)
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