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From "Pete Wyckoff (JIRA)" <j...@apache.org>
Subject [jira] Created: (HADOOP-4108) FileSystem support for POSIX access method
Date Mon, 08 Sep 2008 04:02:44 GMT
FileSystem support for POSIX access method
------------------------------------------

                 Key: HADOOP-4108
                 URL: https://issues.apache.org/jira/browse/HADOOP-4108
             Project: Hadoop Core
          Issue Type: New Feature
          Components: fs
            Reporter: Pete Wyckoff


>From man access:
{code}

 int access(const char *pathname, int mode);
{code}

DESCRIPTION
       access  checks  whether  the process would be allowed to read, write or test for existence
of the file (or other file system object) whose name is pathname.  If pathname is a symbolic
link permissions of the file referred to by this symbolic link are tested.

       mode is a mask consisting of one or more of R_OK, W_OK, X_OK and F_OK.

       R_OK, W_OK and X_OK request checking whether the file exists and has read, write and
execute permissions, respectively.  F_OK just requests checking for the existence of the file.

       The tests depend on the permissions of the directories occurring in the path to the
file, as given in pathname, and on the permissions of directories and files referred to by
symbolic links encountered on the way.

       The check is done with the processâs real uid and gid, rather than with the effective
ids as is done when actually attempting an operation.  This is to allow set-UID  programs
 to
       easily determine the invoking userâs authority.

       Only  access  bits  are checked, not the file type or contents.  Therefore, if a directory
is found to be "writable," it probably means that files can be created in the directory,
       and not that the directory can be written as a file.  Similarly, a DOS file may be
found to be "executable," but the execve(2) call will still fail.

       If the process has appropriate privileges, an implementation may indicate success for
X_OK even if none of the execute file permission bits are set.

RETURN VALUE
       On success (all requested permissions granted), zero is returned.  On error (at least
one bit in mode asked for a permission that is denied, or some other error occurred),  -1
 is
       returned, and errno is set appropriately.



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