NAME
strdup strndup
— duplicate a specific number of bytes from a
string
SYNOPSIS
char *strdup(const char *s); char *strndup(const char *s, size_t size);
DESCRIPTION
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(3). 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(3), 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.
RETURN VALUE
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.
ERRORS
These functions shall fail if:
- [ENOMEM]
- Storage space available is insufficient.
EXAMPLES
None.
APPLICATION USAGE
For functions that allocate memory as if by
malloc(3), the application should release such memory when
it is no longer required by a call to free(3). For
strdup () and strndup (),
this is the return value.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
XBD <string.h>
CHANGE HISTORY
First released in Issue 4, Version 2.
Issue 5
Moved from X/OPEN UNIX extension to BASE.
Issue 7
Austin Group Interpretation 1003.1-2001 #044 is applied, changing the ``may fail'' [ENOMEM] error to become a ``shall fail'' error.
The strdup () function is moved from the
XSI option to the Base.
The strndup () function is added from The
Open Group Technical Standard, 2006, Extended API Set Part 1.
The APPLICATION USAGE section is updated to clarify that memory is allocated as if by malloc(3).