access

Purpose

     Determines the accessibility of a file.

Syntax

     #include <unistd.h>

     int access (path, amode)
     char *path;
     int amode;

Description

     The access  system call  checks the accessibility  of the
     file specified by the path parameter, using the real user
     ID in place  of the effective user ID and  the real group
     ID in place  of the effective group ID.   If the Distrib-
     uted  Services  licensed  program is  installed  on  your
     system,  this  path can  cross  into  another node.   The
     access system  call checks the  named file to see  if the
     type of access  specified by the amode  parameter is per-
     mitted.

     The bit pattern contained in amode is constructed by log-
     ically OR-ing the following values:

         R_OK      Checks read permission.
         W_OK      Checks write permission.
         X_OK      Checks execute (search) permission.
         F_OK      Checks to see if the file exists.

     The owner  of a file  has access checked with  respect to
     the owner read, write, and execute mode bits.  Members of
     the file's group other than the owner have access checked
     with respect  to the  group mode  bits.  All  others have
     access checked with respect to the other mode bits.

Return Value

     If the  requested access  is permitted, a  value of  0 is
     returned.  If the requested access  is denied, a value of
     -1 is returned and errno is set to indicate the error.

Diagnostics

     Access to the  file is denied if one or  more of the fol-
     lowing are true:

     ENOTDIR    A component of the path prefix is not a direc-
                tory.

     ENOENT     Read, write, or execute (search) permission is
                requested for a null path name.

     ENOENT     The named file does not exist.

     EACCES     Search permission is denied  on a component of
                the path prefix.

     EACCES     Permission bits of the file mode do not permit
                the requested access.

     EROFS      Write  access is  requested  for a  file on  a
                read-only file system.

     ETXTBSY    Write access is requested for a pure procedure
                (shared text) file that is being executed.

     EFAULT     The path parameter &pointsout..

     ESTALE     The  process's root  or  current directory  is
                located in a virtual file system that has been
                unmounted.

     If  Distributed Services  is  installed  on your  system,
     access can also fail if one  or more of the following are
     true:

     EDIST         The   server   has  blocked   new   inbound
                   requests.

     EDIST         Outbound requests are currently blocked.

     EDIST         The server has a  release level of Distrib-
                   uted Services that  cannot communicate with
                   this node.

     EAGAIN        The  server  is  too  busy  to  accept  the
                   request.

     ESTALE        The file  descriptor for a remote  file has
                   become obsolete.

     EPERM         The translate tables of  the server did not
                   contain any entry  for either the effective
                   user  ID  or  effective  group  ID  of  the
                   calling process.

     ENODEV        The named file is  a remote file located on
                   a  device that  has been  unmounted at  the
                   server.

     ENOMEM        Either  this node  or the  server does  not
                   have enough memory available to service the
                   request.

     ENOCONNECT    An attempt to establish  a new network con-
                   nection with a remote node failed.

     EBADCONNECT   An attempt to use  an existing network con-
                   nection with a remote node failed.

Related Information

     In this book:  "chmod" and "stat, fstat."