# Module Stdlib.Filename

    module Filename: Filename

    val current_dir_name : string

The conventional name for the current directory (e.g. `.` in Unix).

    val parent_dir_name : string

The conventional name for the parent of the current directory (e.g. `..` in Unix).

    val dir_sep : string

The directory separator (e.g. `/` in Unix).

- Since 3.11.2

    val concat : string -> string -> string

`concat dir file` returns a file name that designates file `file` in directory `dir`.

    val is_relative : string -> bool

Return `true` if the file name is relative to the current directory, `false` if it is absolute (i.e. in Unix, starts with `/`).

    val is_implicit : string -> bool

Return `true` if the file name is relative and does not start with an explicit reference to the current directory (`./` or `../` in Unix), `false` if it starts with an explicit reference to the root directory or the current directory.

    val check_suffix : string -> string -> bool

`check_suffix name suff` returns `true` if the filename `name` ends with the suffix `suff`.

Under Windows ports (including Cygwin), comparison is case-insensitive, relying on `String.lowercase_ascii`. Note that this does not match exactly the interpretation of case-insensitive filename equivalence from Windows.

    val chop_suffix : string -> string -> string

`chop_suffix name suff` removes the suffix `suff` from the filename `name`. The behavior is undefined if `name` does not end with the suffix `suff`. `chop_suffix_opt` is thus recommended instead.

    val chop_suffix_opt : suffix:string -> string -> string option

`chop_suffix_opt ~suffix filename` removes the suffix from the `filename` if possible, or returns `None` if the filename does not end with the suffix.

Under Windows ports (including Cygwin), comparison is case-insensitive, relying on `String.lowercase_ascii`. Note that this does not match exactly the interpretation of case-insensitive filename equivalence from Windows.

- Since 4.08

    val extension : string -> string

`extension name` is the shortest suffix `ext` of `name0` where:

- `name0` is the longest suffix of `name` that does not contain a directory separator;
- `ext` starts with a period;
- `ext` is preceded by at least one non-period character in `name0`.

If such a suffix does not exist, `extension name` is the empty string.

- Since 4.04

    val remove_extension : string -> string

Return the given file name without its extension, as defined in `Filename.extension`. If the extension is empty, the function returns the given file name.

The following invariant holds for any file name `s`:

`remove_extension s ^ extension s = s`

- Since 4.04

    val chop_extension : string -> string

Same as `Filename.remove_extension`, but raise `Invalid_argument` if the given name has an empty extension.

    val basename : string -> string

Split a file name into directory name / base file name. If `name` is a valid file name, then `concat (dirname name) (basename name)` returns a file name which is equivalent to `name`. Moreover, after setting the current directory to `dirname name` (with `Sys.chdir`), references to `basename name` (which is a relative file name) designate the same file as `name` before the call to `Sys.chdir`.

This function conforms to the specification of POSIX.1-2008 for the `basename` utility.

    val dirname : string -> string

See `Filename.basename`. This function conforms to the specification of POSIX.1-2008 for the `dirname` utility.

    val null : string

`null` is `"/dev/null"` on POSIX and `"NUL"` on Windows. It represents a file on the OS that discards all writes and returns end of file on reads.

- Since 4.10.0

    val temp_file : ?temp_dir:string -> string -> string -> string

`temp_file prefix suffix` returns the name of a fresh temporary file in the temporary directory. The base name of the temporary file is formed by concatenating `prefix`, then a suitably chosen integer number, then `suffix`. The optional argument `temp_dir` indicates the temporary directory to use, defaulting to the current result of `Filename.get_temp_dir_name`. The temporary file is created empty, with permissions `0o600` (readable and writable only by the file owner). The file is guaranteed to be different from any other file that existed when `temp_file` was called.

- Before 3.11.2 no ?temp_dir optional argument
- Raises `Sys_error` if the file could not be created.

    val open_temp_file : ?mode:open_flag list ->
           ?perms:int ->
           ?temp_dir:string -> string -> string -> string * out_channel

Same as `Filename.temp_file`, but returns both the name of a fresh temporary file, and an output channel opened (atomically) on this file. This function is more secure than `temp_file`: there is no risk that the temporary file will be modified (e.g. replaced by a symbolic link) before the program opens it. The optional argument `mode` is a list of additional flags to control the opening of the file. It can contain one or several of `Open_append`, `Open_binary`, and `Open_text`. The default is `[Open_text]` (open in text mode). The file is created with permissions `perms` (defaults to readable and writable only by the file owner, `0o600`).

- Before 4.03.0 no ?perms optional argument
- Before 3.11.2 no ?temp_dir optional argument
- Raises `Sys_error` if the file could not be opened.

    val get_temp_dir_name : unit -> string

The name of the temporary directory: Under Unix, the value of the `TMPDIR` environment variable, or "/tmp" if the variable is not set. Under Windows, the value of the `TEMP` environment variable, or "." if the variable is not set. The temporary directory can be changed with `Filename.set_temp_dir_name`.

- Since 4.00.0

    val set_temp_dir_name : string -> unit

Change the temporary directory returned by `Filename.get_temp_dir_name` and used by `Filename.temp_file` and `Filename.open_temp_file`.

- Since 4.00.0

    val temp_dir_name : string

Deprecated. You should use `Filename.get_temp_dir_name` instead.

The name of the initial temporary directory: Under Unix, the value of the `TMPDIR` environment variable, or "/tmp" if the variable is not set. Under Windows, the value of the `TEMP` environment variable, or "." if the variable is not set.

- Since 3.09.1

    val quote : string -> string

Return a quoted version of a file name, suitable for use as one argument in a command line, escaping all meta-characters. Warning: under Windows, the output is only suitable for use with programs that follow the standard Windows quoting conventions.

    val quote_command : string ->
           ?stdin:string -> ?stdout:string -> ?stderr:string -> string list -> string

`quote_command cmd args` returns a quoted command line, suitable for use as an argument to `Sys.command`, `Unix.system`, and the `Unix.open_process` functions.

The string `cmd` is the command to call. The list `args` is the list of arguments to pass to this command. It can be empty.

The optional arguments `?stdin` and `?stdout` and `?stderr` are file names used to redirect the standard input, the standard output, or the standard error of the command. If `~stdin:f` is given, a redirection `< f` is performed and the standard input of the command reads from file `f`. If `~stdout:f` is given, a redirection `> f` is performed and the standard output of the command is written to file `f`. If `~stderr:f` is given, a redirection `2> f` is performed and the standard error of the command is written to file `f`. If both `~stdout:f` and `~stderr:f` are given, with the exact same file name `f`, a `2>&1` redirection is performed so that the standard output and the standard error of the command are interleaved and redirected to the same file `f`.

Under Unix and Cygwin, the command, the arguments, and the redirections if any are quoted using `Filename.quote`, then concatenated. Under Win32, additional quoting is performed as required by the `cmd.exe` shell that is called by `Sys.command`.

- Since 4.10.0
- Raises `Failure` if the command cannot be escaped on the current platform.