'\" et
.TH STRDUP "3P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\"
.SH PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
.\"
.SH NAME
strdup, strndup
\(em duplicate a specific number of bytes from a string
.SH SYNOPSIS
.LP
.nf
#include <string.h>
.P
char *strdup(const char *\fIs\fP);
char *strndup(const char *\fIs\fP, size_t \fIsize\fP);
.fi
.SH DESCRIPTION
The
\fIstrdup\fR()
function shall return a pointer to a new string, which is a duplicate
of the string pointed to by
.IR s .
The returned pointer can be passed to
\fIfree\fR().
A null pointer is returned if the new string cannot be created.
.P
The
\fIstrndup\fR()
function shall be equivalent to the
\fIstrdup\fR()
function, duplicating the provided
.IR s
in a new block of memory allocated as if by using
\fImalloc\fR(),
with the exception being that
\fIstrndup\fR()
copies at most
.IR size
plus one bytes into the newly allocated memory, terminating the new
string with a NUL character. If the length of
.IR s
is larger than
.IR size ,
only
.IR size
bytes shall be duplicated. If
.IR size
is larger than the length of
.IR s ,
all bytes in
.IR s
shall be copied into the new memory buffer, including the terminating
NUL character. The newly created string shall always be properly
terminated.
.SH "RETURN VALUE"
The
\fIstrdup\fR()
function shall return a pointer to a new string on success. Otherwise,
it shall return a null pointer and set
.IR errno
to indicate the error.
.P
Upon successful completion, the
\fIstrndup\fR()
function shall return a pointer to the newly allocated memory
containing the duplicated string. Otherwise, it shall return a null
pointer and set
.IR errno
to indicate the error.
.SH ERRORS
These functions shall fail if:
.TP
.BR ENOMEM
Storage space available is insufficient.
.LP
.IR "The following sections are informative."
.SH EXAMPLES
None.
.SH "APPLICATION USAGE"
For functions that allocate memory as if by
\fImalloc\fR(),
the application should release such memory when it is no longer
required by a call to
\fIfree\fR().
For
\fIstrdup\fR()
and
\fIstrndup\fR(),
this is the return value.
.P
Implementations are free to
\fImalloc\fR()
a buffer containing either (\c
.IR size
+ 1) bytes or (\c
.IR strnlen (
.IR s ,
.IR size )
+ 1) bytes. Applications should not assume that
\fIstrndup\fR()
will allocate (\c
.IR size
+ 1) bytes when
.IR strlen (
.IR s )
is smaller than
.IR size .
.SH RATIONALE
None.
.SH "FUTURE DIRECTIONS"
None.
.SH "SEE ALSO"
.IR "\fIfree\fR\^(\|)",
.IR "\fIwcsdup\fR\^(\|)"
.P
The Base Definitions volume of POSIX.1\(hy2017,
.IR "\fB<string.h>\fP"
.\"
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1-2017, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
In the event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
.PP
Any typographical or formatting errors that appear
in this page are most likely
to have been introduced during the conversion of the source files to
man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .