read, write, append, exist, none
or
execute. File may also be the name of a
directory. Fails silently otherwise. access_file(File, none)
simply succeeds without testing anything.
If Mode is write or append, this
predicate also succeeds if the file does not exist and the user has
write access to the directory of the specified location.
The bahaviour is backed up by the POSIX access() API. The Windows replacement (_waccess()) returns incorrect results because it does not consider ACLs (Access Control Lists). The Prolog flag win_file_access_check may be used to control the level of checking performed by Prolog. Please note that checking access never provides a guarantee that a subsequent open succeeds without errors due to inherent concurrency in file operations. It is generally more robust to try and open the file and handle possible exceptions. See open/4 and catch/3.
/*[^/]*/*$. If
the result is empty it binds Directory to //.//a/b/ into /a/b. Volker
Wysk pointed at this incorrect behaviour.
See also directory_file_path/3
from library(filesex). The system ensures that for every
valid Path using the Prolog (POSIX) directory separators,
following is true on systems with a sound implementation of
same_file/2.138On
some systems, Path and Path2 refer to the same
entry in the file system, but same_file/2
may fail. See also prolog_to_os_filename/2.
...,
file_directory_name(Path, Dir),
file_base_name(Path, File),
directory_file_path(Dir, File, Path2),
same_file(Path, Path2).
/*([^/]*)/*$, now capturing the non-///'') otherwise. The behaviour is consistent with the
POSIX basename program.139Before
SWI-Prolog 7.7.13, if argPath ended with a /st_dev and st_inode, same_file/2
is implemented by comparing the device and inode identifiers. On
Windows,
same_file/2
compares the strings returned by the GetFullPathName() system call.. and .. are
deleted. This predicate ensures that expanding a filename returns the
same absolute path regardless of how the file is addressed. SWI-Prolog
uses absolute filenames to register source files independent of the
current working directory. See also absolute_file_name/3
and expand_file_name/2.(library(lists)), a
relative filename or an absolute filename. The primary intention of this
predicate is to resolve files specified as Alias(Relative).
Option is a list of options to guide the conversion:
''. For each
extension, absolute_file_name/3
will first add the extension and then verify the conditions imposed by
the other options. If the condition fails, the next extension on the
list is tried. Extensions may be specified both as .ext or
plain ext.read, write, append,
execute, exist or none. See also access_file/2.txt implies [''],
prolog implies ['.pl', ''], executable
implies
['.so', ''], qlf implies ['.qlf', '']
and
directory implies ['']. The file type source
is an alias for prolog for compatibility with SICStus
Prolog. See also prolog_file_type/2.
This predicate only returns non-directories, unless the option file_type(directory)
is specified.error (default), throw an existence_error
exception if the file cannot be found. If fail, stay
silent.140Silent operation was the
default up to version 3.2.6.first (default), the predicate leaves no choice point.
Otherwise a choice point will be left and backtracking may yield more
solutions.true (default is false) and Spec
is atomic, call expand_file_name/2
followed by member/2
on Spec before proceeding. This is a SWI-Prolog extension
intended to minimise porting effort after SWI-Prolog stopped expanding
environment variables and the ~*
The Prolog flag verbose_file_search
can be set to true to help debugging Prolog's search for
files.
This predicate is derived from Quintus Prolog. In Quintus Prolog, the
argument order was absolute_file_name(+Spec, +Options, -Path).
The argument order has been changed for compatibility with ISO and
SICStus. The Quintus argument order is still accepted.
<letter>:.
This predicate is intended to provide platform-independent checking for
absolute paths. See also absolute_file_name/2
and prolog_to_os_filename/2...... See also expand_file_name/2.141This
predicate should be considered a misnomer because it returns entries
rather than files. We stick to this name for compatibility with, e.g.,
SICStus, Ciao and YAP.?*[ ... ]' and `{...}'
are recognised. The interpretation of `{...}' is slightly
different from the C shell (csh(1)). The comma-separated argument can be
arbitrary patterns, including `{...}' patterns. The empty
pattern is legal as well: `{.pl,}' matches either `.pl'
or the empty string.
If the pattern contains wildcard characters, only existing files and directories are returned. Expanding a `pattern' without wildcard characters returns the argument, regardless of whether or not it exists.
Before expanding wildcards, the construct $\arg{var} is
expanded to the value of the environment variable var, and a
possible leading ~ character is expanded to the user's home
directory.142On Windows, the home
directory is determined as follows: if the environment variable HOME
exists, this is used. If the variables HOMEDRIVE and HOMEPATH
exist (Windows-NT), these are used. At initialisation, the system will
set the environment variable HOME to point to the
SWI-Prolog home directory if neither HOME nor HOMEPATH
and HOMEDRIVE are defined.
\/Because it is possible to guess the generated filename, attackers may create the filesystem entry as a link and possibly create a security issue. New code should use tmp_file_stream/3.
O_EXCL, which guarantees that
the file did not exist before this call. The following options are
processed:
binary
opens the file in binary mode.This predicate is a safe replacement of tmp_file/2. Note that in those cases where the temporary file is needed to store output from an external command, the file must be closed first. E.g., the following downloads a file from a URL to a temporary file and opens the file for reading (on Unix systems you can delete the file for cleanup after opening it for reading):
open_url(URL, In) :-
tmp_file_stream(text, File, Stream),
close(Stream),
process_create(curl, ['-o', File, URL], []),
open(File, read, In),
delete_file(File). % Unix-only
Temporary files created using this call are removed if the Prolog process terminates gracefully. Calling delete_file/1 using FileName removes the file and removes the entry from the administration of files-to-be-deleted.
working_directory(CWD, CWD) to get the current directory.
See also absolute_file_name/2
and chdir/1.bugSome
of the file I/O predicates use local filenames. Changing directory while
file-bound streams are open causes wrong results on telling/1, seeing/1
and current_stream/3.
Note that the working directory is shared between all threads.