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.\" Copyright (c) 1990, 1991, 1993
.\" The Regents of the University of California. All rights reserved.
.\"
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.\" modification, are permitted provided that the following conditions
.\" are met:
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.\" notice, this list of conditions and the following disclaimer.
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.\" 3. Neither the name of the University nor the names of its contributors
.\" may be used to endorse or promote products derived from this software
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\"
.Dd May 5, 2020
.Dt STRDUP 3
.Os
.Sh NAME
.Nm strdup ,
.Nm strdupa ,
.Nm strndup ,
.Nm strndupa
.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 strdupa "const char *str"
.Ft char *
.Fn strndup "const char *str" "size_t len"
.Ft char *
.Fn strndupa "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 memory is allocated with
.Xr malloc 3
and should be released with
.Xr free 3
when no longer needed.
.Pp
The
.Fn strndup
function copies at most
.Fa len
characters from the string
.Fa str
always
.Dv NUL
terminating the copied string.
.Pp
The
.Fn strdupa
function is identical to
.Fn strdup
but allocates the memory with
.Xr alloca 3 .
Similarly, the
.Fn strndupa
function is identical to
.Fn strndup ,
but allocates the memory with
.Xr alloca 3 .
.Sh RETURN VALUES
If insufficient memory is available, NULL is returned and
.Va errno
is set to
.Er ENOMEM .
Otherwise, the
.Fn strdup
family of functions return a pointer to the copied string.
.Sh SEE ALSO
.Xr alloca 3 ,
.Xr free 3 ,
.Xr malloc 3 ,
.Xr wcsdup 3
.Sh STANDARDS
The
.Fn strdup
function is specified by
.St -p1003.1-2001 .
The
.Fn strndup
function is specified by
.St -p1003.1-2008 .
The
.Fn strdupa
and
.Fn strndupa
functions are extensions,
taken from glibc.
.Sh HISTORY
The
.Fn strdup
function first appeared in
.Bx 4.3 Reno .
The
.Fn strndup
function was added in
.Fx 7.2 .
The
.Fn strdupa
and
.Fn strndupa
functions were added in
.Fx 15.1 .
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