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Technical Reference: Base Operating System and Extensions, Volume 1
Determines the accessibility of a
file.
Standard C Library
(libc.a)
#include <unistd.h>
int access ( PathName, Mode)
char *PathName;
int Mode;
int accessx (PathName, Mode, Who)
char *PathName;
int Mode, Who;
int faccessx ( FileDescriptor, Mode, Who)
int FileDescriptor;
int Mode, Who;
The access,
accessx, and faccessx subroutines determine the
accessibility of a file system object. The accessx and
faccessx subroutines allow the specification of a class of users or
processes for whom access is to be checked.
The caller must have search
permission for all components of the PathName parameter.
| PathName
| Specifies the path name of the file. If the PathName
parameter refers to a symbolic link, the access subroutine returns
information about the file pointed to by the symbolic link.
|
| FileDescriptor
| Specifies the file descriptor of an open file.
|
| Mode
| Specifies the access modes to be checked. This parameter is a bit
mask containing 0 or more of the following values, which are defined in the
sys/access.h file:
- R_OK
- Check read permission.
- W_OK
- Check write permission.
- X_OK
- Check execute or search permission.
- F_OK
- Check the existence of a file.
If none of these values are
specified, the existence of a file is checked.
|
| Who
| Specifies the class of users for whom access is to be checked.
This parameter must be one of the following values, which are defined in the
sys/access.h file:
- ACC_SELF
- Determines if access is permitted for the current process. The
effective user and group IDs, the concurrent group set and the privilege of
the current process are used for the calculation.
- ACC_INVOKER
- Determines if access is permitted for the invoker of the current
process. The real user and group IDs, the concurrent group set, and the
privilege of the invoker are used for the calculation.
Note: The expression access
(PathName, Mode) is
equivalent to accessx (PathName,
Mode, ACC_INVOKER).
- ACC_OTHERS
- Determines if the specified access is permitted for any user other than
the object owner. The Mode parameter must contain only one
of the valid modes. Privilege is not considered in the
calculation.
- ACC_ALL
- Determines if the specified access is permitted for all users. The
Mode parameter must contain only one of the valid modes.
Privilege is not considered in the calculation
.
|
If the requested access is
permitted, the access, accessx, and faccessx
subroutines return a value of 0. If the requested access is not
permitted or the function call fails, a value of -1 is returned and the
errno global variable is set to indicate the error.
The access and
accessx subroutines fail if one or more of the following are
true:
| EACCES
| Search permission is denied on a component of the PathName
prefix.
|
| EFAULT
| The PathName parameter points to a location outside the
allocated address space of the process.
|
| ELOOP
| Too many symbolic links were encountered in translating the
PathName parameter.
|
| ENOENT
| A component of the PathName does not exist or the process has
the disallow truncation attribute set.
|
| ENOTDIR
| A component of the PathName is not a directory.
|
| ESTALE
| The process root or current directory is located in a virtual file system
that has been unmounted.
|
| ENOENT
| The named file does not exist.
|
| ENOENT
| The PathName parameter was null.
|
| ENOENT
| A symbolic link was named, but the file to which it refers does not
exist.
|
| ENAMETOOLONG
| A component of the PathName parameter exceeded 255 characters
or the entire PathName parameter exceeded 1023 characters.
|
The faccessx subroutine
fails if the following is true:
| EBADF
| The value of the FileDescriptor parameter is not valid.
|
The access,
accessx, and faccessx subroutines fail if one or more of
the following is true:
| EIO
| An I/O error occurred during the operation.
|
| EACCES
| The file protection does not allow the requested access.
|
| EROFS
| Write access is requested for a file on a read-only file system.
|
If Network File System (NFS) is
installed on your system, the accessx and faccessx
subroutines can also fail if the following is true:
| ETIMEDOUT
| The connection timed out.
|
| ETXTBSY
| Write access is requested for a shared text file that is being
executed.
|
| EINVAL
| The value of the Mode argument is invalid.
|
These subroutines are part of Base
Operating System (BOS) Runtime.
The acl_get (acl_get or acl_fget Subroutine) subroutine, chacl (chacl or fchacl Subroutine) subroutine, statx subroutine, statacl subroutine.
The aclget command, aclput command, chmod command, chown command.
Files, Directories,
and File Systems for Programmers in AIX 5L Version 5.1 General
Programming Concepts: Writing and Debugging Programs.
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