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.\"     @(#)strdup.3	8.1 (Berkeley) 6/9/93
.\"
.Dd $Mdocdate: December 1 2015 $
.Dt STRDUP 3
.Os
.Sh NAME
.Nm strdup ,
.Nm strndup
.Nd save a copy of a string
.Sh SYNOPSIS
.In string.h
.Ft char *
.Fn strdup "const char *s"
.Ft char *
.Fn strndup "const char *s" "size_t maxlen"
.Sh DESCRIPTION
The
.Fn strdup
function allocates sufficient memory for a copy of the string
.Fa s ,
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
The
.Fn strndup
function behaves similarly to
.Nm strdup
but only copies up to
.Fa maxlen
characters from
.Fa s .
The resulting string is always NUL-terminated.
.Pp
If the memory allocation fails,
.Dv NULL
is returned.
.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;

p = strdup("foobar");
if (p == NULL)
	err(1, NULL);
.Ed
.Sh ERRORS
The
.Fn strdup
and
.Fn strndup
functions 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 strlcpy 3 ,
.Xr strlen 3 ,
.Xr wcsdup 3
.Sh STANDARDS
The
.Fn strdup
and
.Fn strndup
functions conform to
.St -p1003.1-2008 .
.Sh HISTORY
A
.Fn strdup
macro was first used in the
.Bx 4.1c
debugger,
.Sy dbx .
It was rewritten as a C function for the
.Bx 4.3
.Xr inetd 8
and first appeared in the C library of
.Bx 4.3 Reno .
The
.Fn strndup
function appeared in glibc 2.0, was reimplemented for
.Nx 4.0 ,
and ported to
.Ox 4.8 .