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File Name Manipulation Functions

The module filename provides a number of useful functions for analyzing and manipulating file names. These functions are designed so that the Erlang code can work on many different platforms with different formats for file names. With file name is meant all strings that can be used to denote a file. They can be short relative names like foo.erl, very long absolute name which include a drive designator and directory names like D:\usr/local\bin\erl/lib\tools\foo.erl, or any variations in between.

In Windows, all functions return file names with forward slashes only, even if the arguments contain back slashes. Use the join/1 function to normalize a file name by removing redundant directory separators.

All functions take either a flat list of characters (a "string") or an atom, or a deep list of strings and atoms. The file module accepts filename in the same form. The return value will always be a flat list of characters.

Types

filename = string() | atom() | [filename()]

Types:

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

Examples include:

Assume (for UNIX) current directory "/usr/local"
Assume (for WIN32) current directory "D:/usr/local"
  
(for UNIX):  absname("foo") -> "/usr/local/foo"
(for WIN32): absname("foo") -> "D:/usr/local/foo"
(for UNIX):  absname("../x") -> "/usr/local/../x"
(for WIN32): absname("../x") -> "D:/usr/local/../x"
(for UNIX):  absname("/") -> "/"
(for WIN32): absname("/") -> "D:/"
        

Types:

This function works like absname/1, except that the directory to which the file name should be made relative is given explicitly in the Directory argument.

Types:

Joins an absolute directory with a relative filename. The same as join/2 but more magical. It also assumes that Directory is an absolute directory and Filename is a relative filename. Might crash otherwise.

The magic consists in that on some platforms, namely they who have tight restrictions on raw filename length, leading parent directory components in Filename are matched against trailing directory components in Directory so they can be removed from the result - minimizing it's length.

On the other hand, on platforms that support symbolic links such magic is magically not performed since it would not work.

Types:

Returns the part of the Filename after the last directory separator, or the Filename itself if it has no separators.

Examples include:

basename("foo") -> "foo"
basename("/usr/foo") -> "foo"
basename("/") -> []
        

Types:

Returns the last component of Filename with the extension Ext stripped. Use this function if you want to to remove an extension which might, or might not, be there. Use rootname(basename(Filename)) if you want to remove an extension that exists, but you are not sure which one it is.

Examples include:

basename("~/src/kalle.erl", ".erl") -> "kalle"
basename("~/src/kalle.beam", ".erl") -> "kalle.beam"
basename("~/src/kalle.old.erl", ".erl") -> "kalle.old"
rootname(basename("~/src/kalle.erl")) -> "kalle"
rootname(basename("~/src/kalle.beam")) -> "kalle"
        

Types:

Returns the directory part of Filename.

Examples include:

dirname("/usr/src/kalle.erl") -> "/usr/src"
dirname("kalle.erl") -> "."
On Win32:  
filename:dirname("\\usr\\src/kalle.erl") -> "/usr/src"
          

Types:

Given a file name string Filename, this function returns the file extension including the period. Returns an empty list if there is no extension.

Examples include:

extension("foo.erl") -> ".erl"
extension("beam.src/kalle") -> []
        

Types:

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

Types:

Joins a list of file name Components with directory separators. If one of the elements in the Components list includes an absolute path, for example "/xxx", the preceding elements, if any, are removed from the result.

The result of the join function is "normalized":

• There are no redundant directory separators.
• In Windows, all directory separators are forward slashes and the drive letter is in lower case.

Examples include:

join("/usr/local", "bin") -> "/usr/local/bin"
join(["/usr", "local", "bin"]) -> "/usr/local/bin"
join(["a/b///c/"] -> "a/b/c"
join(["B:a\\b///c/"] -> "b:a/b/c"  % On Windows only
        

Types:

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

Types:

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

Example:

(on UNIX)  filename:nativename("/usr/local/bin/") -> "/usr/local/bin"
(on Win32) filename:nativename("/usr/local/bin/") -> "\\usr\\local\\bin"

Returns one of absolute, relative, or volumerelative.

absolute

The path name refers to a specific file on a specific volume.
Examples include:

on Unix
/usr/local/bin/
on Windows
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.
Examples include:

In Windows
D:bar.erl, /bar/foo.erl
/temp
            

Types:

rootname/1 returns all characters in Filename, except the extension.

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

Examples include:

rootname("/beam.src/kalle") -> "/beam.src/kalle"
rootname("/beam.src/foo.erl") -> "/beam.src/foo"
rootname("/beam.src/foo.erl",".erl") -> "/beam.src/foo"
rootname("/beam.src/foo.beam",".erl") -> "/beam.src/foo.beam"
        

Types:

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

Examples include:

split("/usr/local/bin") -> ["/", "usr", "local", "bin"]
split("foo/bar") -> ["foo", "bar"]
split("a:\\msdev\\include") -> ["a:/", "msdev", "include"]
        

Types:

Finds the source file name and compilation options for a compiled module. The result can be fed to compile:file/2 in order to compile the file again.

The Module argument, which can be a string or an atom, specifies either the module name or the path to the source code, with or without the ".erl" extension. In either case, the module must be known by the code manager, i.e. code:which/1 must succeed.

Rules describe how the source directory is found, when the object code directory is known. Each rule is of the form {BinSuffix, SourceSuffix} and is interpreted as follows: If the end of the directory name where the object is located matches BinSuffix, then the suffix of the directory name is replaced by SourceSuffix. If the source file is found in the resulting directory, then the function returns that location together with Options. Otherwise, the next rule is tried, and so on.

The function returns {SourceFile, Options}. SourceFile is the absolute path to the source file without the ".erl" extension. Options include the options which are necessary to compile the file with compile:file/2, but excludes options such as report or verbose which do not change the way code is generated. The paths in the {outdir, Path} and {i, Path} options are guaranteed to be absolute.

Björn Gustavsson - support@erlang.ericsson.se