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PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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STRDUP(3P) POSIX Programmer's Manual STRDUP(3P)
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.
strdup, strndup — duplicate a specific number of bytes from a
string
#include <string.h>
char *strdup(const char *s);
char *strndup(const char *s, size_t size);
The strdup() function shall return a pointer to a new string,
which is a duplicate of the string pointed to by s. The returned
pointer can be passed to free(). A null pointer is returned if
the new string cannot be created.
The strndup() function shall be equivalent to the strdup()
function, duplicating the provided s in a new block of memory
allocated as if by using malloc(), with the exception being that
strndup() copies at most size plus one bytes into the newly
allocated memory, terminating the new string with a NUL character.
If the length of s is larger than size, only size bytes shall be
duplicated. If size is larger than the length of s, all bytes in s
shall be copied into the new memory buffer, including the
terminating NUL character. The newly created string shall always
be properly terminated.
The strdup() function shall return a pointer to a new string on
success. Otherwise, it shall return a null pointer and set errno
to indicate the error.
Upon successful completion, the strndup() function shall return a
pointer to the newly allocated memory containing the duplicated
string. Otherwise, it shall return a null pointer and set errno to
indicate the error.
These functions shall fail if:
ENOMEM Storage space available is insufficient.
The following sections are informative.
None.
For functions that allocate memory as if by malloc(), the
application should release such memory when it is no longer
required by a call to free(). For strdup() and strndup(), this is
the return value.
Implementations are free to malloc() a buffer containing either
(size + 1) bytes or (strnlen( s, size) + 1) bytes. Applications
should not assume that strndup() will allocate (size + 1) bytes
when strlen( s) is smaller than size.
None.
None.
free(3p), wcsdup(3p)
The Base Definitions volume of POSIX.1‐2017, string.h(0p)
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 .
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 .
IEEE/The Open Group 2017 STRDUP(3P)
Pages that refer to this page: string.h(0p), strndup(3p), wcsdup(3p)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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