.TH filename 3erl "stdlib 4.3.1.3" "Ericsson AB" "Erlang Module Definition"
.SH NAME
filename \- Filename manipulation functions.
.SH DESCRIPTION
.LP
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 \fIfoo\&.erl\fR\&, a long absolute name including a drive designator, a directory name like \fID:\\usr/local\\bin\\erl/lib\\tools\\foo\&.erl\fR\&, or any variations in between\&.
.LP
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 \fIjoin/1\fR\&\&.
.LP
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 \fIfile:native_name_encoding/0\fR\&, a raw filename is also returned\&. For example, \fIjoin/1\fR\& 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 \fIfile\fR\& module\&.
.LP

.RS -4
.B
Note:
.RE
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\&.
.LP
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 containing null characters inside the filename are now \fIrejected\fR\& and will cause primitive file operations to fail\&.

.LP

.RS -4
.B
Warning:
.RE
Currently null characters at the end of the filename will be accepted by primitive file operations\&. Such filenames are however still documented as invalid\&. The implementation will also change in the future and reject such filenames\&.

.SH EXPORTS
.LP
.nf

.B
absname(Filename) -> file:filename_all()
.br
.fi
.br
.RS
.LP
Types:

.RS 3
Filename = file:name_all()
.br
.RE
.RE
.RS
.LP
Converts a relative \fIFilename\fR\& 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\&.
.LP
\fIUnix examples:\fR\&
.LP
.nf

1> pwd()\&.
"/usr/local"
2> filename:absname("foo")\&.
"/usr/local/foo"
3> filename:absname("\&.\&./x")\&.
"/usr/local/../x"
4> filename:absname("/")\&.
"/"
.fi
.LP
\fIWindows examples:\fR\&
.LP
.nf

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:/"
.fi
.RE

.LP
.nf

.B
absname(Filename, Dir) -> file:filename_all()
.br
.fi
.br
.RS
.LP
Types:

.RS 3
Filename = Dir = file:name_all()
.br
.RE
.RE
.RS
.LP
Same as \fIabsname/1\fR\&, except that the directory to which the filename is to be made relative is specified in argument \fIDir\fR\&\&.
.RE

.LP
.nf

.B
absname_join(Dir, Filename) -> file:filename_all()
.br
.fi
.br
.RS
.LP
Types:

.RS 3
Dir = Filename = file:name_all()
.br
.RE
.RE
.RS
.LP
Joins an absolute directory with a relative filename\&. Similar to \fIjoin/2\fR\&, but on platforms with tight restrictions on raw filename length and no support for symbolic links, leading parent directory components in \fIFilename\fR\& are matched against trailing directory components in \fIDir\fR\& so they can be removed from the result - minimizing its length\&.
.RE

.LP
.nf

.B
basedir(PathType, Application) -> file:filename_all()
.br
.fi
.br
.nf

.B
basedir(PathsType, Application) -> [file:filename_all()]
.br
.fi
.br
.RS
.LP
Types:

.RS 3
PathType = basedir_path_type()
.br
PathsType = basedir_paths_type()
.br
Application = string() | binary()
.br
.nf
\fBbasedir_path_type()\fR\& = 
.br
    user_cache | user_config | user_data | user_log
.fi
.br
.nf
\fBbasedir_paths_type()\fR\& = site_config | site_data
.fi
.br
.RE
.RE
.RS
.LP
Equivalent to  basedir(PathType, Application, #{}) or  basedir(PathsType, Application, #{})\&.
.RE

.LP
.nf

.B
basedir(PathType, Application, Opts) -> file:filename_all()
.br
.fi
.br
.nf

.B
basedir(PathsType, Application, Opts) -> [file:filename_all()]
.br
.fi
.br
.RS
.LP
Types:

.RS 3
PathType = basedir_path_type()
.br
PathsType = basedir_paths_type()
.br
Application = string() | binary()
.br
Opts = basedir_opts()
.br
.nf
\fBbasedir_path_type()\fR\& = 
.br
    user_cache | user_config | user_data | user_log
.fi
.br
.nf
\fBbasedir_paths_type()\fR\& = site_config | site_data
.fi
.br
.nf
\fBbasedir_opts()\fR\& = 
.br
    #{author => string() | binary(),
.br
      os => windows | darwin | linux,
.br
      version => string() | binary()}
.fi
.br
.RE
.RE
.RS
.LP
Returns a suitable path, or paths, for a given type\&. If \fIos\fR\& is not set in \fIOpts\fR\& the function will default to the native option, that is \fI\&'linux\&'\fR\&, \fI\&'darwin\&'\fR\& or \fI\&'windows\&'\fR\&, as understood by \fIos:type/0\fR\&\&. Anything not recognized as \fI\&'darwin\&'\fR\& or \fI\&'windows\&'\fR\& is interpreted as \fI\&'linux\&'\fR\&\&.
.LP
The options \fI\&'author\&'\fR\& and \fI\&'version\&'\fR\& are only used with \fI\&'windows\&'\fR\& option mode\&.
.RS 2
.TP 2
*
\fIuser_cache\fR\&
.RS 2
.LP
The path location is intended for transient data files on a local machine\&.
.RE

.RS 2
.LP
On Linux: Respects the os environment variable \fIXDG_CACHE_HOME\fR\&\&.
.RE

.LP
.nf

1> filename:basedir(user_cache, "my_application", #{os=>linux})\&.
"/home/otptest/.cache/my_application"
.fi On Darwin: 
.LP
.nf

1> filename:basedir(user_cache, "my_application", #{os=>darwin})\&.
"/home/otptest/Library/Caches/my_application"
.fi On Windows: 
.LP
.nf

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"
.fi
.LP
.TP 2
*
\fIuser_config\fR\&
.RS 2
.LP
The path location is intended for persistent configuration files\&.
.RE

.RS 2
.LP
On Linux: Respects the os environment variable \fIXDG_CONFIG_HOME\fR\&\&.
.RE

.LP
.nf

2> filename:basedir(user_config, "my_application", #{os=>linux})\&.
"/home/otptest/.config/my_application"
.fi On Darwin:
.LP
.nf

2> filename:basedir(user_config, "my_application", #{os=>darwin})\&.
"/home/otptest/Library/Application Support/my_application"
.fi On Windows:
.LP
.nf

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"
.fi
.LP
.TP 2
*
\fIuser_data\fR\&
.RS 2
.LP
The path location is intended for persistent data files\&.
.RE

.RS 2
.LP
On Linux: Respects the os environment variable \fIXDG_DATA_HOME\fR\&\&.
.RE

.LP
.nf

3> filename:basedir(user_data, "my_application", #{os=>linux})\&.
"/home/otptest/.local/my_application"
.fi On Darwin:
.LP
.nf

3> filename:basedir(user_data, "my_application", #{os=>darwin})\&.
"/home/otptest/Library/Application Support/my_application"
.fi On Windows:
.LP
.nf

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"
.fi
.LP
.TP 2
*
\fIuser_log\fR\&
.RS 2
.LP
The path location is intended for transient log files on a local machine\&.
.RE

.RS 2
.LP
On Linux: Respects the os environment variable \fIXDG_CACHE_HOME\fR\&\&.
.RE

.LP
.nf

4> filename:basedir(user_log, "my_application", #{os=>linux})\&.
"/home/otptest/.cache/my_application/log"
.fi On Darwin:
.LP
.nf

4> filename:basedir(user_log, "my_application", #{os=>darwin})\&.
"/home/otptest/Library/Logs/my_application"
.fi On Windows:
.LP
.nf

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"
.fi
.LP
.TP 2
*
\fIsite_config\fR\&
.RS 2
.LP
On Linux: Respects the os environment variable \fIXDG_CONFIG_DIRS\fR\&\&.
.RE

.LP
.nf

5> filename:basedir(site_config, "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"]
.fi On Darwin:
.LP
.nf

5> filename:basedir(site_config, "my_application", #{os=>darwin})\&.
["/Library/Application Support/my_application"]
.fi
.LP
.TP 2
*
\fIsite_data\fR\&
.RS 2
.LP
On Linux: Respects the os environment variable \fIXDG_DATA_DIRS\fR\&\&.
.RE

.LP
.nf

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"]
.fi On Darwin:
.LP
.nf

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

.RE

.LP
.nf

.B
basename(Filename) -> file:filename_all()
.br
.fi
.br
.RS
.LP
Types:

.RS 3
Filename = file:name_all()
.br
.RE
.RE
.RS
.LP
Returns the last component of \fIFilename\fR\&, or \fIFilename\fR\& itself if it does not contain any directory separators\&.
.LP
\fIExamples:\fR\&
.LP
.nf

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

.LP
.nf

.B
basename(Filename, Ext) -> file:filename_all()
.br
.fi
.br
.RS
.LP
Types:

.RS 3
Filename = Ext = file:name_all()
.br
.RE
.RE
.RS
.LP
Returns the last component of \fIFilename\fR\& with extension \fIExt\fR\& 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 \fIrootname(basename(Filename))\fR\&\&.
.LP
\fIExamples:\fR\&
.LP
.nf

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"
.fi
.RE

.LP
.nf

.B
dirname(Filename) -> file:filename_all()
.br
.fi
.br
.RS
.LP
Types:

.RS 3
Filename = file:name_all()
.br
.RE
.RE
.RS
.LP
Returns the directory part of \fIFilename\fR\&\&.
.LP
\fIExamples:\fR\&
.LP
.nf

13> filename:dirname("/usr/src/kalle\&.erl")\&.
"/usr/src"
14> filename:dirname("kalle\&.erl")\&.
"."
.fi
.LP
.nf

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

.LP
.nf

.B
extension(Filename) -> file:filename_all()
.br
.fi
.br
.RS
.LP
Types:

.RS 3
Filename = file:name_all()
.br
.RE
.RE
.RS
.LP
Returns the file extension of \fIFilename\fR\&, including the period\&. Returns an empty string if no extension exists\&.
.LP
\fIExamples:\fR\&
.LP
.nf

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

.LP
.nf

.B
flatten(Filename) -> file:filename_all()
.br
.fi
.br
.RS
.LP
Types:

.RS 3
Filename = file:name_all()
.br
.RE
.RE
.RS
.LP
Converts a possibly deep list filename consisting of characters and atoms into the corresponding flat string filename\&.
.RE

.LP
.nf

.B
join(Components) -> file:filename_all()
.br
.fi
.br
.RS
.LP
Types:

.RS 3
Components = [file:name_all()]
.br
.RE
.RE
.RS
.LP
Joins a list of filename \fIComponents\fR\& with directory separators\&. If one of the elements of \fIComponents\fR\& includes an absolute path, such as \fI"/xxx"\fR\&, the preceding elements, if any, are removed from the result\&.
.LP
The result is "normalized":
.RS 2
.TP 2
*
Redundant directory separators are removed\&.
.LP
.TP 2
*
In Windows, all directory separators are forward slashes and the drive letter is in lower case\&.
.LP
.RE

.LP
\fIExamples:\fR\&
.LP
.nf

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

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

.LP
.nf

.B
join(Name1, Name2) -> file:filename_all()
.br
.fi
.br
.RS
.LP
Types:

.RS 3
Name1 = Name2 = file:name_all()
.br
.RE
.RE
.RS
.LP
Joins two filename components with directory separators\&. Equivalent to \fIjoin([Name1, Name2])\fR\&\&.
.RE

.LP
.nf

.B
nativename(Path) -> file:filename_all()
.br
.fi
.br
.RS
.LP
Types:

.RS 3
Path = file:name_all()
.br
.RE
.RE
.RS
.LP
Converts \fIPath\fR\& 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 \fIjoin/1\fR\&\&.
.LP
\fIExamples:\fR\&
.LP
.nf

19> filename:nativename("/usr/local/bin/")\&. % Unix
"/usr/local/bin"
.fi
.LP
.nf

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

.LP
.nf

.B
pathtype(Path) -> absolute | relative | volumerelative
.br
.fi
.br
.RS
.LP
Types:

.RS 3
Path = file:name_all()
.br
.RE
.RE
.RS
.LP
Returns the path type, which is one of the following:
.RS 2
.TP 2
.B
\fIabsolute\fR\&:
The path name refers to a specific file on a specific volume\&.
.RS 2
.LP
Unix example: \fI/usr/local/bin\fR\&
.RE

.RS 2
.LP
Windows example: \fID:/usr/local/bin\fR\&
.RE

.TP 2
.B
\fIrelative\fR\&:
The path name is relative to the current working directory on the current volume\&.
.RS 2
.LP
Example: \fIfoo/bar, \&.\&./src\fR\&
.RE

.TP 2
.B
\fIvolumerelative\fR\&:
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\&.
.RS 2
.LP
Windows example: \fID:bar\&.erl, /bar/foo\&.erl\fR\&
.RE

.RE
.RE

.LP
.nf

.B
rootname(Filename) -> file:filename_all()
.br
.fi
.br
.nf

.B
rootname(Filename, Ext) -> file:filename_all()
.br
.fi
.br
.RS
.LP
Types:

.RS 3
Filename = Ext = file:name_all()
.br
.RE
.RE
.RS
.LP
Removes a filename extension\&. \fIrootname/2\fR\& works as \fIrootname/1\fR\&, except that the extension is removed only if it is \fIExt\fR\&\&.
.LP
\fIExamples:\fR\&
.LP
.nf

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"
.fi
.RE

.LP
.nf

.B
split(Filename) -> Components
.br
.fi
.br
.RS
.LP
Types:

.RS 3
Filename = file:name_all()
.br
Components = [file:name_all()]
.br
.RE
.RE
.RS
.LP
Returns a list whose elements are the path components of \fIFilename\fR\&\&.
.LP
\fIExamples:\fR\&
.LP
.nf

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"]
.fi
.RE