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.\"     from: @(#)strdup.3	8.1 (Berkeley) 6/9/93
.\"	$NetBSD: strdup.3,v 1.19 2024/12/09 12:09:02 nros Exp $
.\"
.Dd December 9, 2024
.Dt STRDUP 3
.Os
.Sh NAME
.Nm strdup ,
.Nm strndup
.Nd save a copy of a string
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In string.h
.Ft char *
.Fn strdup "const char *str"
.Ft char *
.Fn strndup "const char *str" "size_t len"
.Sh DESCRIPTION
The
.Fn strdup
function
allocates sufficient memory for a copy
of the string
.Fa str ,
does the copy, and returns a pointer to it.
The pointer may subsequently be used as an
argument to the function
.Xr free 3 .
.Pp
If insufficient memory is available,
.Dv NULL
is returned.
.Pp
The
.Fn strndup
function copies at most
.Fa len
characters from the string
.Fa str
always
.Dv NUL
terminating the copied string.
.Sh EXAMPLES
The following will point
.Va p
to an allocated area of memory containing the nul-terminated string
.Qq foobar :
.Bd -literal -offset indent
char *p;

if ((p = strdup("foobar")) == NULL) {
	fprintf(stderr, "Out of memory.\en");
	exit(1);
}
.Ed
.Sh ERRORS
The
.Fn strdup
function may fail and set the external variable
.Va errno
for any of the errors specified for the library function
.Xr malloc 3 .
.Sh SEE ALSO
.Xr free 3 ,
.Xr malloc 3 ,
.Xr strcpy 3 ,
.Xr strlen 3
.Sh STANDARDS
The
.Fn strdup
function conforms to
.St -p1003.1-2001 .
The
.Fn strdup
and
.Fn strndup
functions conform to
.St -isoC-2023 .
.Sh HISTORY
The
.Fn strdup
function first appeared in
.Bx 4.4 .
The
.Fn strndup
function was added in
.Nx 4.0 .