Provided by: erlang-manpages_25.3.2.12+dfsg-1ubuntu2_all 
NAME
filelib - File utilities, such as wildcard matching of filenames.
DESCRIPTION
This module contains utilities on a higher level than the file module.
This module does not support "raw" filenames (that is, files whose names do not comply with the expected
encoding). Such files are ignored by the functions in this module.
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.
DATA TYPES
filename() = file:name()
dirname() = filename()
dirname_all() = filename_all()
filename_all() = file:name_all()
find_file_rule() =
{ObjDirSuffix :: string(), SrcDirSuffix :: string()}
find_source_rule() =
{ObjExtension :: string(),
SrcExtension :: string(),
[find_file_rule()]}
EXPORTS
ensure_dir(Name) -> ok | {error, Reason}
Types:
Name = filename_all() | dirname_all()
Reason = file:posix()
Ensures that all parent directories for the specified file or directory name Name exist, trying to
create them if necessary.
Returns ok if all parent directories already exist or can be created. Returns {error, Reason} if
some parent directory does not exist and cannot be created.
ensure_path(Path) -> ok | {error, Reason}
Types:
Path = dirname_all()
Reason = file:posix()
Ensures that all parent directories for the specified path Path exist, trying to create them if
necessary.
Unlike ensure_dir/1, this function will attempt to create all path segments as a directory,
including the last segment.
Returns ok if all parent directories already exist or can be created. Returns {error, Reason} if
some parent directory does not exist and cannot be created.
file_size(Filename) -> integer() >= 0
Types:
Filename = filename_all()
Returns the size of the specified file.
fold_files(Dir, RegExp, Recursive, Fun, AccIn) -> AccOut
Types:
Dir = dirname()
RegExp = string()
Recursive = boolean()
Fun = fun((F :: file:filename(), AccIn) -> AccOut)
AccIn = AccOut = term()
Folds function Fun over all (regular) files F in directory Dir whose basename (for example, just
"baz.erl" in "foo/bar/baz.erl") matches the regular expression RegExp (for a description of the
allowed regular expressions, see the re module). If Recursive is true, all subdirectories to Dir
are processed. The regular expression matching is only done on the filename without the directory
part.
If Unicode filename translation is in effect and the file system is transparent, filenames that
cannot be interpreted as Unicode can be encountered, in which case the fun() must be prepared to
handle raw filenames (that is, binaries). If the regular expression contains codepoints > 255, it
does not match filenames that do not conform to the expected character encoding (that is, are not
encoded in valid UTF-8).
For more information about raw filenames, see the file module.
is_dir(Name) -> boolean()
Types:
Name = filename_all() | dirname_all()
Returns true if Name refers to a directory, otherwise false.
is_file(Name) -> boolean()
Types:
Name = filename_all() | dirname_all()
Returns true if Name refers to a file or a directory, otherwise false.
is_regular(Name) -> boolean()
Types:
Name = filename_all()
Returns true if Name refers to a (regular) file, otherwise false.
last_modified(Name) -> file:date_time() | 0
Types:
Name = filename_all() | dirname_all()
Returns the date and time the specified file or directory was last modified, or 0 if the file does
not exist.
wildcard(Wildcard) -> [file:filename()]
Types:
Wildcard = filename() | dirname()
Returns a list of all files that match Unix-style wildcard string Wildcard.
The wildcard string looks like an ordinary filename, except that the following "wildcard
characters" are interpreted in a special way:
?:
Matches one character.
*:
Matches any number of characters up to the end of the filename, the next dot, or the next
slash.
**:
Two adjacent * used as a single pattern match all files and zero or more directories and
subdirectories.
[Character1,Character2,...]:
Matches any of the characters listed. Two characters separated by a hyphen match a range of
characters. Example: [A-Z] matches any uppercase letter.
{Item,...}:
Alternation. Matches one of the alternatives.
Other characters represent themselves. Only filenames that have exactly the same character in the
same position match. Matching is case-sensitive, for example, "a" does not match "A".
Directory separators must always be written as /, even on Windows.
A character preceded by \ loses its special meaning. Note that \ must be written as \\ in a string
literal. For example, "\\?*" will match any filename starting with ?.
Notice that multiple "*" characters are allowed (as in Unix wildcards, but opposed to Windows/DOS
wildcards).
Examples:
The following examples assume that the current directory is the top of an Erlang/OTP installation.
To find all .beam files in all applications, use the following line:
filelib:wildcard("lib/*/ebin/*.beam").
To find .erl or .hrl in all applications src directories, use either of the following lines:
filelib:wildcard("lib/*/src/*.?rl")
filelib:wildcard("lib/*/src/*.{erl,hrl}")
To find all .hrl files in src or include directories:
filelib:wildcard("lib/*/{src,include}/*.hrl").
To find all .erl or .hrl files in either src or include directories:
filelib:wildcard("lib/*/{src,include}/*.{erl,hrl}")
To find all .erl or .hrl files in any subdirectory:
filelib:wildcard("lib/**/*.{erl,hrl}")
wildcard(Wildcard, Cwd) -> [file:filename()]
Types:
Wildcard = filename() | dirname()
Cwd = dirname()
Same as wildcard/1, except that Cwd is used instead of the working directory.
find_file(Filename :: filename(), Dir :: filename()) ->
{ok, filename()} | {error, not_found}
find_file(Filename :: filename(),
Dir :: filename(),
Rules :: [find_file_rule()]) ->
{ok, filename()} | {error, not_found}
Looks for a file of the given name by applying suffix rules to the given directory path. For
example, a rule {"ebin", "src"} means that if the directory path ends with "ebin", the
corresponding path ending in "src" should be searched.
If Rules is left out or is an empty list, the default system rules are used. See also the Kernel
application parameter source_search_rules.
find_source(FilePath :: filename()) ->
{ok, filename()} | {error, not_found}
Equivalent to find_source(Base, Dir), where Dir is filename:dirname(FilePath) and Base is
filename:basename(FilePath).
find_source(Filename :: filename(), Dir :: filename()) ->
{ok, filename()} | {error, not_found}
find_source(Filename :: filename(),
Dir :: filename(),
Rules :: [find_source_rule()]) ->
{ok, filename()} | {error, not_found}
Applies file extension specific rules to find the source file for a given object file relative to
the object directory. For example, for a file with the extension .beam, the default rule is to
look for a file with a corresponding extension .erl by replacing the suffix "ebin" of the object
directory path with "src" or "src/*". The file search is done through find_file/3. The directory
of the object file is always tried before any other directory specified by the rules.
If Rules is left out or is an empty list, the default system rules are used. See also the Kernel
application parameter source_search_rules.
safe_relative_path(Filename, Cwd) -> unsafe | SafeFilename
Types:
Filename = Cwd = SafeFilename = filename_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.
* A symbolic link in the path points above the root of the relative path.
Examples:
1> {ok, Cwd} = file:get_cwd().
...
2> filelib:safe_relative_path("dir/sub_dir/..", Cwd).
"dir"
3> filelib:safe_relative_path("dir/..", Cwd).
[]
4> filelib:safe_relative_path("dir/../..", Cwd).
unsafe
5> filelib:safe_relative_path("/abs/path", Cwd).
unsafe