Availability:built-in
access_file(+File,
+Mode)True if File exists and can be accessed by this Prolog
process under mode Mode. Mode is one of the atoms
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.
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