# Module `Eliom_lib.Filename`

```ocaml
val current_dir_name : string
```
The conventional name for the current directory (e.g. `.` in Unix).

```ocaml
val parent_dir_name : string
```
The conventional name for the parent of the current directory (e.g. `..` in Unix).

```ocaml
val dir_sep : string
```
The directory separator (e.g. `/` in Unix).

since 3\.11.2
```ocaml
val concat : string -> string -> string
```
`concat dir file` returns a file name that designates file `file` in directory `dir`.

```ocaml
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 `/`).

```ocaml
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.

```ocaml
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.

```ocaml
val chop_suffix : string -> string -> string
```
`chop_suffix name suff` removes the suffix `suff` from the filename `name`.

raises [`Invalid_argument`](./../../ocaml-compiler/stdlib/Stdlib.md#exception-Invalid_argument) if name does not end with the suffix suff.
```ocaml
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
```ocaml
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
```ocaml
val remove_extension : string -> string
```
Return the given file name without its extension, as defined in [`Filename.extension`](./#val-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
```ocaml
val chop_extension : string -> string
```
Same as [`Filename.remove_extension`](./#val-remove_extension), but raise `Invalid_argument` if the given name has an empty extension.

```ocaml
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`](./../../ocaml-compiler/stdlib/Stdlib-Sys.md#val-chdir)), references to `basename name` (which is a relative file name) designate the same file as `name` before the call to [`Sys.chdir`](./../../ocaml-compiler/stdlib/Stdlib-Sys.md#val-chdir).

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

```ocaml
val dirname : string -> string
```
See [`Filename.basename`](./#val-basename). This function conforms to the specification of POSIX.1-2008 for the `dirname` utility.

```ocaml
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
```ocaml
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`](./#val-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.

raises [`Sys_error`](./../../ocaml-compiler/stdlib/Stdlib.md#exception-Sys_error) if the file could not be created.
before 3\.11.2 no ?temp\_dir optional argument
```ocaml
val open_temp_file : 
  ?mode:open_flag list ->
  ?perms:int ->
  ?temp_dir:string ->
  string ->
  string ->
  string * out_channel
```
Same as [`Filename.temp_file`](./#val-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`).

raises [`Sys_error`](./../../ocaml-compiler/stdlib/Stdlib.md#exception-Sys_error) if the file could not be opened.
before 4\.03 no ?perms optional argument
before 3\.11.2 no ?temp\_dir optional argument
```ocaml
val temp_dir : ?temp_dir:string -> ?perms:int -> string -> string -> string
```
`temp_dir prefix suffix` creates and returns the name of a fresh temporary directory with permissions `perms` (defaults to 0o700) inside `temp_dir`. The base name of the temporary directory 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`](./#val-get_temp_dir_name). The temporary directory is created empty, with permissions `0o700` (readable, writable, and searchable only by the file owner). The directory is guaranteed to be different from any other directory that existed when `temp_dir` was called.

If temp\_dir does not exist, this function does not create it. Instead, it raises Sys\_error.

raises [`Sys_error`](./../../ocaml-compiler/stdlib/Stdlib.md#exception-Sys_error) if the directory could not be created.
since 5\.1
```ocaml
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 returned by `GetTempPath2` (if available) or `GetTempPath`.

The temporary directory can be changed with [`Filename.set_temp_dir_name`](./#val-set_temp_dir_name).

Under Windows, before OCaml 5\.4, it would return the value of the `TEMP` environment variable, or "." if the variable was not set.

since 4\.00
```ocaml
val set_temp_dir_name : string -> unit
```
Change the temporary directory returned by [`Filename.get_temp_dir_name`](./#val-get_temp_dir_name) and used by [`Filename.temp_file`](./#val-temp_file) and [`Filename.open_temp_file`](./#val-open_temp_file). The temporary directory is a domain-local value which is inherited by child domains.

since 4\.00
```ocaml
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.

```ocaml
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`](./../../ocaml-compiler/stdlib/Stdlib-Sys.md#val-command), [`Unix.system`](./../../ocaml-compiler/unix/Unix.md#val-system), and the [`Unix.open_process`](./../../ocaml-compiler/unix/Unix.md#val-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`](./#val-quote), then concatenated. Under Win32, additional quoting is performed as required by the `cmd.exe` shell that is called by [`Sys.command`](./../../ocaml-compiler/stdlib/Stdlib-Sys.md#val-command).

raises [`Failure`](./../../ocaml-compiler/stdlib/Stdlib.md#exception-Failure) if the command cannot be escaped on the current platform.
since 4\.10
```ocaml
val extension_no_directory : string -> string
```