20.3 File System
A number of built-in predicates is provided for dealing with files and
Here we consider only the file as a whole, for opening files and accessing
their contents refer to chapter 10.
20.3.1 Current Directory
The current working directory is an important notion in UNIX.
It can be read and changed within the ECLiPSe system by using getcwd/1 and
The current working directory is accessible as a global flag as well.
Reading and writing this flag is equivalent to the use of getcwd/1 and
All ECLiPSe built-ins that take file names as arguments accept absolute
pathnames as well as relative pathnames starting at the current directory.
[eclipse 1]: getcwd(Where).
Where = "/usr/name/prolog"
[eclipse 2]: cd(..).
[eclipse 3]: get_flag(cwd, Where)
Where = "/usr/name"
20.3.2 Looking at Directories
To look at the contents of a directory, read_directory/4 is available.
It takes a directory pathname and a filename pattern and returns a list
of subdirectories and a list of files matching the pattern.
The following metacharacters are recognised in the pattern:
* matches an arbitrary sequence of characters,
? matches any single character,  matches one of the
characters inside the brackets unless the first one is a in which case it matches any character but those inside the brackets.
[eclipse 1]: read_directory("/usr/john", "*", Dirlist, Filelist).
Dirlist = ["subdir1", "subdir2"]
Filelist = ["one.c", "two.c", "three.pl", "four.pl"]
20.3.3 Checking Files
For checking the existence of files,
exists/1 or the more powerful
existing_file/4 is used.
For accessing any file properties there is get_file_info/3.
It can return file permissions, type, owner, size, inode, number of
links as well as creation, access and modification times
(as defined by the UNIX system call stat(2); not all entries are
meaningful under Windows), and accessibility
It fails when the specified file does not exist.
Refer to the reference manual or help/1 for details.
20.3.4 Renaming and Removing Files
For these basic operations with files, rename/2 and delete/1
The filenames used by ECLiPSe is in the Unix format, including on Window
platforms, with the addition that the disk such as
//C/, so a Windows filename such as
"C:\my\path\name.ecl" should be writen as
"//C/my/path/name.pl". The utility os_file_name/2 provides for
the interconversion between the format used in ECLiPSe and the Operating
The utility pathname/4
is provided to ease the handling of filenames.
It takes a full pathname and cuts it into the directory
pathname, the filename proper and a suffix (
the part beginning with the last dot in the string).
It also expands symbolic pathnames, starting with
[eclipse 1]: Name = "~octopus/prolog/file.pl",
pathname(Name, Path, File, Suffix).
Path = "/usr/octopus/prolog/"
File = "file.pl"
Name = "~octopus/prolog/file.pl"
Suffix = ".pl"