Converts a relative Filename and returns an absolute name. No attempt is made to create the shortest absolute name, as this can give incorrect results on file systems that allow links.

Unix examples:

1> pwd().
"/usr/local"
2> filename:absname("foo").
"/usr/local/foo"
3> filename:absname("../x").
"/usr/local/../x"
4> filename:absname("/").
"/"

Windows examples:

1> pwd().
"D:/usr/local"
2> filename:absname("foo").
"D:/usr/local/foo"
3> filename:absname("../x").
"D:/usr/local/../x"
4> filename:absname("/").
"D:/"

Same as absname/1, except that the directory to which the filename is to be made relative is specified in argument Dir.

Joins an absolute directory with a relative filename. Similar to join/2, but on platforms with tight restrictions on raw filename length and no support for symbolic links (read: VxWorks), leading parent directory components in Filename are matched against trailing directory components in Dir so they can be removed from the result - minimizing its length.

Equivalent to basedir(PathType, Application, #{}) or basedir(PathsType, Application, #{}).

Returns a suitable path, or paths, for a given type. If os is not set in Opts the function will default to the native option, that is 'linux', 'darwin' or 'windows', as understood by os:type/0. Anything not recognized as 'darwin' or 'windows' is interpreted as 'linux'.

The options 'author' and 'version' are only used with 'windows' option mode.

• user_cache

  The path location is intended for transient data files on a local machine.

  On Linux: Respects the os environment variable XDG_CACHE_HOME.

  1> filename:basedir(user_cache, "my_application", #{os=>linux}).
  "/home/otptest/.cache/my_application"

  On Darwin:

  1> filename:basedir(user_cache, "my_application", #{os=>darwin}).
  "/home/otptest/Library/Caches/my_application"

  On Windows:

  1> filename:basedir(user_cache, "My App").
  "c:/Users/otptest/AppData/Local/My App/Cache"
  2> filename:basedir(user_cache, "My App").
  "c:/Users/otptest/AppData/Local/My App/Cache"
  3> filename:basedir(user_cache, "My App", #{author=>"Erlang"}).
  "c:/Users/otptest/AppData/Local/Erlang/My App/Cache"
  4> filename:basedir(user_cache, "My App", #{version=>"1.2"}).
  "c:/Users/otptest/AppData/Local/My App/1.2/Cache"
  5> filename:basedir(user_cache, "My App", #{author=>"Erlang",version=>"1.2"}).
  "c:/Users/otptest/AppData/Local/Erlang/My App/1.2/Cache"

• user_config

  The path location is intended for persistent configuration files.

  On Linux: Respects the os environment variable XDG_CONFIG_HOME.

  2> filename:basedir(user_config, "my_application", #{os=>linux}).
  "/home/otptest/.config/my_application"

  On Darwin:

  2> filename:basedir(user_config, "my_application", #{os=>darwin}).
  "/home/otptest/Library/Application Support/my_application"

  On Windows:

  1> filename:basedir(user_config, "My App").
  "c:/Users/otptest/AppData/Roaming/My App"
  2> filename:basedir(user_config, "My App", #{author=>"Erlang", version=>"1.2"}).
  "c:/Users/otptest/AppData/Roaming/Erlang/My App/1.2"

• user_data

  The path location is intended for persistent data files.

  On Linux: Respects the os environment variable XDG_DATA_HOME.

  3> filename:basedir(user_data, "my_application", #{os=>linux}).
  "/home/otptest/.local/my_application"

  On Darwin:

  3> filename:basedir(user_data, "my_application", #{os=>darwin}).
  "/home/otptest/Library/Application Support/my_application"

  On Windows:

  8> filename:basedir(user_data, "My App").
  "c:/Users/otptest/AppData/Local/My App"
  9> filename:basedir(user_data, "My App",#{author=>"Erlang",version=>"1.2"}).
  "c:/Users/otptest/AppData/Local/Erlang/My App/1.2"

• user_log

  The path location is intended for transient log files on a local machine.

  On Linux: Respects the os environment variable XDG_CACHE_HOME.

  4> filename:basedir(user_log, "my_application", #{os=>linux}).
  "/home/otptest/.cache/my_application/log"

  On Darwin:

  4> filename:basedir(user_log, "my_application", #{os=>darwin}).
  "/home/otptest/Library/Caches/my_application"

  On Windows:

  12> filename:basedir(user_log, "My App").
  "c:/Users/otptest/AppData/Local/My App/Logs"
  13> filename:basedir(user_log, "My App",#{author=>"Erlang",version=>"1.2"}).
  "c:/Users/otptest/AppData/Local/Erlang/My App/1.2/Logs"

• site_config

  On Linux: Respects the os environment variable XDG_CONFIG_DIRS.

  5> filename:basedir(site_data, "my_application", #{os=>linux}).
  ["/usr/local/share/my_application",
   "/usr/share/my_application"]
  6> os:getenv("XDG_CONFIG_DIRS").
  "/etc/xdg/xdg-ubuntu:/usr/share/upstart/xdg:/etc/xdg"
  7> filename:basedir(site_config, "my_application", #{os=>linux}).
  ["/etc/xdg/xdg-ubuntu/my_application",
   "/usr/share/upstart/xdg/my_application",
   "/etc/xdg/my_application"]
  8> os:unsetenv("XDG_CONFIG_DIRS").
  true
  9> filename:basedir(site_config, "my_application", #{os=>linux}).
  ["/etc/xdg/my_application"]

  On Darwin:

  5> filename:basedir(site_config, "my_application", #{os=>darwin}).
  ["/Library/Application Support/my_application"]

• site_data

  On Linux: Respects the os environment variable XDG_DATA_DIRS.

  10> os:getenv("XDG_DATA_DIRS").
  "/usr/share/ubuntu:/usr/share/gnome:/usr/local/share/:/usr/share/"
  11> filename:basedir(site_data, "my_application", #{os=>linux}).
  ["/usr/share/ubuntu/my_application",
   "/usr/share/gnome/my_application",
   "/usr/local/share/my_application",
   "/usr/share/my_application"]
  12> os:unsetenv("XDG_DATA_DIRS").
  true
  13> filename:basedir(site_data, "my_application", #{os=>linux}).
  ["/usr/local/share/my_application",
   "/usr/share/my_application"]

  On Darwin:

  5> filename:basedir(site_data, "my_application", #{os=>darwin}).
  ["/Library/Application Support/my_application"]

Returns the last component of Filename, or Filename itself if it does not contain any directory separators.

Examples:

5> filename:basename("foo").
"foo"
6> filename:basename("/usr/foo").
"foo"
7> filename:basename("/").
[]

Returns the last component of Filename with extension Ext stripped. This function is to be used to remove a (possible) specific extension. To remove an existing extension when you are unsure which one it is, use rootname(basename(Filename)).

Examples:

8> filename:basename("~/src/kalle.erl", ".erl").
"kalle"
9> filename:basename("~/src/kalle.beam", ".erl").
"kalle.beam"
10> filename:basename("~/src/kalle.old.erl", ".erl").
"kalle.old"
11> filename:rootname(filename:basename("~/src/kalle.erl")).
"kalle"
12> filename:rootname(filename:basename("~/src/kalle.beam")).
"kalle"

Returns the directory part of Filename.

Examples:

13> filename:dirname("/usr/src/kalle.erl").
"/usr/src"
14> filename:dirname("kalle.erl").
"."

5> filename:dirname("\\usr\\src/kalle.erl"). % Windows
"/usr/src"

Returns the file extension of Filename, including the period. Returns an empty string if no extension exists.

Examples:

15> filename:extension("foo.erl").
".erl"
16> filename:extension("beam.src/kalle").
[]

Converts a possibly deep list filename consisting of characters and atoms into the corresponding flat string filename.

Joins a list of filename Components with directory separators. If one of the elements of Components includes an absolute path, such as "/xxx", the preceding elements, if any, are removed from the result.

The result is "normalized":

• Redundant directory separators are removed.
• In Windows, all directory separators are forward slashes and the drive letter is in lower case.

Examples:

17> filename:join(["/usr", "local", "bin"]).
"/usr/local/bin"
18> filename:join(["a/b///c/"]).
"a/b/c"

6> filename:join(["B:a\\b///c/"]). % Windows
"b:a/b/c"

Joins two filename components with directory separators. Equivalent to join([Name1, Name2]).

Converts Path to a form accepted by the command shell and native applications on the current platform. On Windows, forward slashes are converted to backward slashes. On all platforms, the name is normalized as done by join/1.

Examples:

19> filename:nativename("/usr/local/bin/"). % Unix
"/usr/local/bin"

7> filename:nativename("/usr/local/bin/"). % Windows
"\\usr\\local\\bin"

Returns the path type, which is one of the following:

absolute

The path name refers to a specific file on a specific volume.

Unix example: /usr/local/bin

Windows example: D:/usr/local/bin

relative

The path name is relative to the current working directory on the current volume.

Example: foo/bar, ../src

volumerelative

The path name is relative to the current working directory on a specified volume, or it is a specific file on the current working volume.

Windows example: D:bar.erl, /bar/foo.erl

Removes a filename extension. rootname/2 works as rootname/1, except that the extension is removed only if it is Ext.

Examples:

20> filename:rootname("/beam.src/kalle").
"/beam.src/kalle"
21> filename:rootname("/beam.src/foo.erl").
"/beam.src/foo"
22> filename:rootname("/beam.src/foo.erl", ".erl").
"/beam.src/foo"
23> filename:rootname("/beam.src/foo.beam", ".erl").
"/beam.src/foo.beam"

Sanitizes the relative path by eliminating ".." and "." components to protect against directory traversal attacks. Either returns the sanitized path name, or the atom unsafe if the path is unsafe. The path is considered unsafe in the following circumstances:

• The path is not relative.

• A ".." component would climb up above the root of the relative path.

Examples:

1> filename:safe_relative_path("dir/sub_dir/..").
"dir"
2> filename:safe_relative_path("dir/..").
[]
3> filename:safe_relative_path("dir/../..").
unsafe
4> filename:safe_relative_path("/abs/path").
unsafe

Returns a list whose elements are the path components of Filename.

Examples:

24> filename:split("/usr/local/bin").
["/","usr","local","bin"]
25> filename:split("foo/bar").
["foo","bar"]
26> filename:split("a:\\msdev\\include").
["a:/","msdev","include"]