Provided by: erlang-manpages_20.2.2+dfsg-1ubuntu2_all 
NAME
filename - Filename manipulation functions.
DESCRIPTION
This module provides functions for analyzing and manipulating filenames. 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 including 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 performed of course). For more information about raw filenames, see the file module.
DATA TYPES
basedir_type() =
user_cache |
user_config |
user_data |
user_log |
site_config |
site_data
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 filename 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),
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.
basedir(Type, Application) -> file:filename_all()
Types:
Type = basedir_type()
Application = string() | binary()
Equivalent to basedir(Type, Application, #{}).
basedir(Type, Application, Opts) -> file:filename_all()
Types:
Type = basedir_type()
Application = string() | binary()
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_CONFIG_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_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"]
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").
[]
find_src(Beam) ->
{SourceFile, Options} | {error, {ErrorReason, Module}}
find_src(Beam, Rules) ->
{SourceFile, Options} | {error, {ErrorReason, Module}}
Types:
Beam = Module | Filename
Filename = atom() | string()
Rules = [{BinSuffix :: string(), SourceSuffix :: string()}]
Module = module()
SourceFile = string()
Options = [Option]
Option =
{i, Path :: string()} |
{outdir, Path :: string()} |
{d, atom()}
ErrorReason = non_existing | preloaded | interpreted
Finds the source filename and compiler options for a module. The result can be fed to
compile:file/2 to compile the file again.
Warning:
This function is deprecated. Use filelib:find_source/1 instead for finding source files.
If possible, use the beam_lib(3erl) module to extract the compiler options and the abstract code
format from the Beam file and compile that instead.
Argument Beam, which can be a string or an atom, specifies either the module name or the path to
the source code, with or without extension ".erl". In either case, the module must be known by the
code server, that is, code:which(Module) must succeed.
Rules describes how the source directory can be found when the object code directory is known. It
is a list of tuples {BinSuffix, SourceSuffix} and is interpreted as follows: if the end of the
directory name where the object is located matches BinSuffix, then the source code directory has
the same name, but with BinSuffix replaced by SourceSuffix. Rules defaults to:
[{"", ""}, {"ebin", "src"}, {"ebin", "esrc"}]
If the source file is found in the resulting directory, the function returns that location
together with Options. Otherwise the next rule is tried, and so on.
The function returns {SourceFile, Options} if it succeeds. SourceFile is the absolute path to the
source file without extension ".erl". Options includes the options that are necessary to recompile
the file with compile:file/2, but excludes options such as report and verbose, which do not change
the way code is generated. The paths in options {outdir, Path} and {i, Path} are guaranteed to be
absolute.
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. Equivalent 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 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
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 "." 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
split(Filename) -> Components
Types:
Filename = file:name_all()
Components = [file:name_all()]
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"]
Ericsson AB stdlib 3.4.3 filename(3erl)