[ Operating System | The ECLiPSe Built-In Predicates | Reference Manual | Alphabetic Index ]

# get_file_info(+File, ?Attr, -Value)

Succeeds if the file File (with absolute or relative pathname) exists and the value of its attribute Attr unfies with Value.

File
  Atom or string.
Attr
  Atom or variable.
Value
  Constant or variable.

## Description

This predicate is used to test the properties of a specified file, it allows to examine the values obtained from the stat(2) system call. Attr specifies one of the attributes listed below or a variable, on return, Value is unified with the attribute value.

The possible attributes and their meanings are:

        Attribute  Meaning
       ----------------------------------
        mode       file mode; see
                   values below
        inode      inode number
        nlink      number of links
        uid        user ID of the
                   owner
        uname      user name of the
                   owner
        gid        group ID of the
                   owner
        gname      group name of the
                   owner
        size       file size
        atime      time of last access
        adate      date of last access
        mtime      time of last data
                   modification
        mdate      date of last data
                   modification
        ctime      time of last status
                   change
        cdate      date of last status
                   change
        readable   on or off
        writable   on or off
        executable on or off

All attributes are integers except for the *name attributes, which are string representation of the corresponding *id attributes and *date attributes, which are string representation of the corresponding *time attributes. The time for the *time attributes is measured as seconds elapsed since 00:00:00 GMT, Jan. 1, 1970. The flags readable, writable and executable indicate whether the running ECLiPSe process has the corresponding permissions on the file. Note that the executable permission for Windows may be approximate, because Windows (especially Vista) have a different system for dealing with execute permission. The meaning of the bits in the mode attribute is as follows:

     Mode     Meaning
    ------------------------------------------------
     8'170000 file type
     8'040000 directory
     8'020000 character special
     8'060000 block special
     8'100000 normal file
     8'120000 symbolic link
     8'140000 socket
    ------------------------------------------------
     8'004000 set user ID on execution
     8'002000 set group ID on execution
    ------------------------------------------------
     8'000700 owner access
     8'000400 read permission for owner
     8'000200 write permission for owner
    ------------------------------------------------
     8'000070 group access
     8'000040 read permission for group
     8'000020 write permission for group
    ------------------------------------------------
     8'000007 other access
     8'000004 read permission for others
     8'000002 write permission for others
     8'000001 execute/search permission for others

The bit masks can be defined as user arithmetic functors so that the code is more readable (see the examples).

### Modes and Determinism

- get_file_info(+, -, -) is nondet
- get_file_info(+, +, -) is semidet

### Fail Conditions

Fails if the file File does not exist, or doesn't have the attribute Attr

### Exceptions

(4) instantiation fault
  File is not instantiated.
(5) type error
  File is neither an atom nor a string.
(5) type error
  Attr is instantiated but not to an atom.
(5) type error
  Value is instantiated but not to a constant.

## Examples

    Success:
       file_type(8'170000).

       directory_flag(8'40000).

       owner_read(8'400).

       is_directory(File) :-
            get_file_info(File, mode, Mode),
            Mode /\ file_type =:= directory_flag.
       readable(File) :-
            get_file_info(File, mode, Mode),
            Mode /\ owner_read =:= owner_read.

       % A file is younger if its time is greater
       is_younger(File1, File2) :-
            get_file_info(File1, mtime) > get_file_info(File2, mtime).

    Fail:
       get_file_info(nofile, mode, Mode).
       get_file_info('/', mode, 8'100000).

    Error:
       get_file_info(File, ctime, T).                (Error 4).
       get_file_info([file], gid, G).                (Error 5).
       get_file_info(file, 1, X).                    (Error 5).

## See Also

exists / 1, delete / 1, exec / 3, local_time / 8, local_time_string / 3