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unlink
Removes a link from a file.
Syntax
#include <unistd.h>
int unlink (const char *pathname);
Parameters
pathname A pointer to a string containing the pathname of a file to
unlink (purge). The pathname must be terminated by a null
character.
Return Values
0 Success.
-1 An error occurred. The file is not unlinked, and errno is set
to indicate the error condition.
Description
The unlink() function removes the link name specified by pathname. It
removes the filename pointed to by pathname from the parent directory,
then decrements the file link count. When the link count of the file
becomes zero and no process has the file open, the file is purged from
the system and is no longer accessible.
If one or more processes have the file open when the link count becomes
zero, the file is not purged until all references to the file have been
closed.
Upon successful completion, unlink() marks for update the st_ctime and
st_mtime time fields of the parent directory.
Implementation Considerations
Refer to the EFAULT, EIMPL, EPERM, and ESYSERR error descriptions below.
POSIX/iX does not support using unlink() on directories. Instead, use
rmdir() to remove a directory.
POSIX/iX does not support multiple hard links to files or soft links to
files or directories.
Every file has a link count of 1 when created. Files being unlinked
cause the link count of the file to be decremented from 1 to 0.
Errors
If an error occurs, errno is set to one of the following values:
EACCES CAUSE The calling process either does not have search
permission to a component of the pathname or does not
have write permission to the parent directory.
ACTION Make sure that the calling process has search
permission for all components of the pathname and
write permission to the parent directory.
EFAULT CAUSE The system detected a NULL or bad address in
attempting to use the pathname parameter or the
pathname was not terminated by a null character.
ACTION Make sure that the pointer is correctly initialized.
EIMPL CAUSE The pathname begins with two slash characters (//).
ACTION Do not begin pathnames with two slash characters
(//).
ENAMETOOLONG CAUSE One of the following:
* The length of the pathname exceeds the
{PATH_MAX} limit (defined in the file
<limits.h>).
* A component of the pathname is longer than
{NAME_MAX} (defined in <limits.h>), and
{_POSIX_NO_TRUNC} is in effect for that
directory.
ACTION Make sure that both the component's length and the
full pathname length do not exceed the {NAME_MAX} or
{PATH_MAX} limits.
Table 4-0. (cont.)
ENOENT CAUSE The specified file does not exist, or pathname points
to an empty string.
ACTION Specify a valid pathname.
ENOTDIR CAUSE A component of the pathname is not a directory.
ACTION Specify a valid pathname.
EPERM CAUSE The specified file is a directory.
ACTION Do not attempt to unlink a directory. Use rmdir()
instead.
ESYSERR CAUSE An operating system error has occurred that does not
map directly to any of the above errors.
ACTION Examine the MPE/iX error stack for the type of system
error.
See Also
close(), open(), rmdir(), POSIX.1 (Section 5.5.1)