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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.

   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 containing 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 documented 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 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, 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(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_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/Logs/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_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"]

                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. 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"

       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"]