filename - Filename manipulation functions.
Please see following description for synopsis
filename(3) Erlang Module Definition filename(3)
NAME
filename - Filename manipulation functions.
DESCRIPTION
This module provides functions for analyzing and manipulating file-
names. These functions are designed so that the Erlang code can work on
many different platforms with different filename formats. With filename
is meant all strings that can be used to denote a file. The filename
can be a short relative name like foo.erl, a long absolute name includ-
ing a drive designator, a directory name like
D:\usr/local\bin\erl/lib\tools\foo.erl, or any variations in between.
In Windows, all functions return filenames with forward slashes only,
even if the arguments contain backslashes. To normalize a filename by
removing redundant directory separators, use join/1.
The module supports raw filenames in the way that if a binary is
present, or the filename cannot be interpreted according to the return
value of file:native_name_encoding/0, a raw filename is also returned.
For example, join/1 provided with a path component that is a binary
(and cannot be interpreted under the current native filename encoding)
results in a raw filename that is returned (the join operation is per-
formed of course). For more information about raw filenames, see the
file module.
Note:
Functionality in this module generally assumes valid input and does not
necessarily fail on input that does not use a valid encoding, but may
instead very likely produce invalid output.
File operations used to accept filenames containing null characters
(integer value zero). This caused the name to be truncated and in some
cases arguments to primitive operations to be mixed up. Filenames con-
taining null characters inside the filename are now rejected and will
cause primitive file operations to fail.
Warning:
Currently null characters at the end of the filename will be accepted
by primitive file operations. Such filenames are however still docu-
mented as invalid. The implementation will also change in the future
and reject such filenames.
EXPORTS
absname(Filename) -> file:filename_all()
Types:
Filename = file:name_all()
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:/"
absname(Filename, Dir) -> file:filename_all()
Types:
Filename = Dir = file:name_all()
Same as absname/1, except that the directory to which the file-
name is to be made relative is specified in argument Dir.
absname_join(Dir, Filename) -> file:filename_all()
Types:
Dir = Filename = file:name_all()
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), lead-
ing parent directory components in Filename are matched against
trailing directory components in Dir so they can be removed from
the result - minimizing its length.
basedir(PathType, Application) -> file:filename_all()
basedir(PathsType, Application) -> [file:filename_all()]
Types:
PathType = basedir_path_type()
PathsType = basedir_paths_type()
Application = string() | binary()
basedir_path_type() =
user_cache | user_config | user_data | user_log
basedir_paths_type() = site_config | site_data
Equivalent to basedir(PathType, Application, #{}) or
basedir(PathsType, Application, #{}).
basedir(PathType, Application, Opts) -> file:filename_all()
basedir(PathsType, Application, Opts) -> [file:filename_all()]
Types:
PathType = basedir_path_type()
PathsType = basedir_paths_type()
Application = string() | binary()
Opts = basedir_opts()
basedir_path_type() =
user_cache | user_config | user_data | user_log
basedir_paths_type() = site_config | site_data
basedir_opts() =
#{author => string() | binary(),
os => windows | darwin | linux,
version => string() | binary()}
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"
1> filename:basedir(user_cache, "my_application", #{os=>darwin}).
"/home/otptest/Library/Caches/my_application"
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_CON-
FIG_HOME.
2> filename:basedir(user_config, "my_application", #{os=>linux}).
"/home/otptest/.config/my_application"
2> filename:basedir(user_config, "my_application", #{os=>darwin}).
"/home/otptest/Library/Application Support/my_application"
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"
3> filename:basedir(user_data, "my_application", #{os=>darwin}).
"/home/otptest/Library/Application Support/my_application"
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"
4> filename:basedir(user_log, "my_application", #{os=>darwin}).
"/home/otptest/Library/Caches/my_application"
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_CON-
FIG_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"]
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"]
5> filename:basedir(site_data, "my_application", #{os=>darwin}).
["/Library/Application Support/my_application"]
basename(Filename) -> file:filename_all()
Types:
Filename = file:name_all()
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("/").
[]
basename(Filename, Ext) -> file:filename_all()
Types:
Filename = Ext = file:name_all()
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"
dirname(Filename) -> file:filename_all()
Types:
Filename = file:name_all()
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"
extension(Filename) -> file:filename_all()
Types:
Filename = file:name_all()
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").
[]
flatten(Filename) -> file:filename_all()
Types:
Filename = file:name_all()
Converts a possibly deep list filename consisting of characters
and atoms into the corresponding flat string filename.
join(Components) -> file:filename_all()
Types:
Components = [file:name_all()]
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"
join(Name1, Name2) -> file:filename_all()
Types:
Name1 = Name2 = file:name_all()
Joins two filename components with directory separators. Equiva-
lent to join([Name1, Name2]).
nativename(Path) -> file:filename_all()
Types:
Path = file:name_all()
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"
pathtype(Path) -> absolute | relative | volumerelative
Types:
Path = file:name_all()
Returns the path type, which is one of the following:
absolute:
The path name refers to a specific file on a specific vol-
ume.
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 cur-
rent working volume.
Windows example: D:bar.erl, /bar/foo.erl
rootname(Filename) -> file:filename_all()
rootname(Filename, Ext) -> file:filename_all()
Types:
Filename = Ext = file:name_all()
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"
safe_relative_path(Filename) -> unsafe | SafeFilename
Types:
Filename = SafeFilename = file:name_all()
Sanitizes the relative path by eliminating ".." and "." compo-
nents 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 cir-
cumstances:
* The path is not relative.
* A ".." component would climb up above the root of the rela-
tive path.
Warning:
This function is deprecated. Use filelib:safe_relative_path/2
instead for sanitizing paths.
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
split(Filename) -> Components
Types:
Filename = file:name_all()
Components = [file:name_all()]
Returns a list whose elements are the path components of File-
name.
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"]
Ericsson AB stdlib 3.17 filename(3)