Module: FileSystem

A file utilities library

The FileSystem module focuses on file and directory properties and operations. It does not cover every interaction involving a file— for instance, path-specific operations live in the Path module, while routines for opening, writing to, or reading from a file live in the IO module. Rather, it covers cases where the user would prefer a file or directory to be handled wholesale and/or with minimal interaction. For example, this module contains File/Directory Manipulations and functions for determining the File/Directory Properties. Also included are operations relating to the current process’s file system state, which are performed on a specified locale (Locale State Functionality). The module also contains iterators for traversing the file system (File System Traversal Iterators).

Locale State Functionality

locale.chdir locale.cwd locale.umask

File System Traversal Iterators

glob listdir walkdirs findfiles

Constant and Function Definitions

const S_IRUSR: int

S_IRUSR and the following constants are values of the form S_I[R | W | X][USR | GRP | OTH], S_IRWX[U | G | O], S_ISUID, S_ISGID, or S_ISVTX, where R corresponds to readable, W corresponds to writable, X corresponds to executable, USR and U correspond to user, GRP and G correspond to group, OTH and O correspond to other, directly tied to the C idea of these constants as visible at GNU Permissions. They are intended for use when dealing with the permissions of files or directories, such as with chmod, getMode, mkdir, or umask

S_IRUSR refers to the user’s read permission

const S_IWUSR: int

Refers to the user’s write permission, see S_IRUSR

const S_IXUSR: int

Refers to the user’s executable permission, see S_IRUSR

const S_IRWXU: int

Refers to all the user’s permissions - read, write, and execute. See S_IRUSR

const S_IRGRP: int

Refers to the group’s read permission, see S_IRUSR

const S_IWGRP: int

Refers to the group’s write permission, see S_IRUSR

const S_IXGRP: int

Refers to the group’s executable permission, see S_IRUSR

const S_IRWXG: int

Refers to all the permissions - read, write, and execute - of those in this group, see S_IRUSR

const S_IROTH: int

Refers to everyone else’s read permission, see S_IRUSR

const S_IWOTH: int

Refers to everyone else’s write permission, see S_IRUSR

const S_IXOTH: int

Refers to everyone else’s executable permission, see S_IRUSR

const S_IRWXO: int

Refers to all the permissions - read, write, and execute - of everyone else, see S_IRUSR

const S_ISUID: int

Use of this would cause the user id to be set on execution. See GNU Permissions for what that generally means, and S_IRUSR for intended uses, etc.

const S_ISGID: int

Use of this would cause the group id to be set on execution. See GNU Permissions for what that generally means, and S_IRUSR for intended uses, etc.

const S_ISVTX: int

This is the sticky bit. See GNU Permissions for what that generally means, and S_IRUSR for intended uses, etc.

proc locale.chdir(name: string)

Change the current working directory of the locale in question to the specified path name.

Will halt with an error message if one is detected.

Warning

This is not safe within a parallel context. A chdir call in one task will affect the current working directory of all tasks for that locale.

Arguments:name : string – The intended current working directory
proc chmod(name: string, mode: int)

Set the permissions of the file or directory specified by the argument name to that indicated by the argument mode.

Will halt with an error message if one is detected

Arguments:
  • name : string – The name of the file or directory whose permissions should be alterred.
  • mode : int – The permissions desired for the file or direcory in question. See description of S_IRUSR, for instance, for potential values.
proc chown(name: string, uid: int, gid: int)

Change one or both of the owner and group id of the named file or directory to the specified values. If uid or gid are -1, the value in question will remain unchanged.

Halts with an error message if one occurred.

Arguments:
  • name : string – The name of the file to be changed.
  • uid : int – The intended new owner(user) id, or -1 if it should remain the same.
  • gid : int – The intended new group owner(id), or -1 if it should remain the same.
proc copy(src: string, dest: string, metadata: bool = false)

Copies the contents and permissions of the file indicated by src into the file or directory dest. If dest is a directory, will halt with an error message. If metadata is set to true, will also copy the metadata (uid, gid, time of last access and time of modification) of the file to be copied.

May halt with other error messages.

Note

In the future, when the Path module has been expanded further, this function will be able to support directories for the dest argument.

Arguments:
  • src : string – The source file whose contents and permissions are to be copied
  • dest : string – The name of the destination file for the contents and permissions. May or may not exist previously, but will be overwritten if it did exist
  • metadata : bool – This argument indicates whether to copy metadata associated with the source file. It is set to false by default.
proc copyFile(src: string, dest: string)

Copies the contents of the file indicated by src into the file indicated by dest, replacing dest‘s contents if it already exists (and is a different file than src, i.e. not a symbolic link to src).

If dest is not writable, or src and dest refer to the same file, this function will halt with an error message. Does not copy metadata. May halt with other error messages.

Arguments:
  • src : string – The source file whose contents are to be copied.
  • dest : string – The intended destination of the contents.
proc copyMode(src: string, dest: string)

Copies the permissions of the file indicated by src to the file indicated by dest, leaving contents, owner and group unaffected.

Will halt with an error message if one is detected.

Arguments:
  • src : string – The source file whose permissions are to be copied.
  • dest : string – The intended destination of the permissions.
proc copyTree(src: string, dest: string, copySymbolically: bool = false)

Will recursively copy the tree which lives under src into dst, including all contents, permissions, and metadata. dst must not previously exist, this function assumes it can create it and any missing parent directories. If copySymbolically is true, symlinks will be copied as symlinks, otherwise their contents and metadata will be copied instead.

Will halt with an error message if one is detected.

Arguments:
  • src : string – The root of the source tree to be copied.
  • dest : string – The root of the destination directory under which the contents of src are to be copied (must not exist prior to this function call).
  • copySymbolically : bool – This argument is used to indicate how to handle symlinks in the source directory. It is set to false by default
proc locale.cwd(): string

Obtains and returns the current working directory for this locale.

Will halt with an error message if one was detected.

Warning

Another task on this locale can change the current working directory from underneath this task, so use caution when making use of this method in a parallel environment.

Returns:The current working directory for the locale in question.
Return type:string
proc exists(name: string): bool

Determines if the file or directory indicated by name exists and returns the result of this check.

Will halt with an error message if one was detected.

Arguments:name : string – The file or directory whose existence is in question.
Returns:true if the provided argument corresponds to an existing file or directory, false otherwise. Also returns false for broken symbolic links.
Return type:bool
iter findfiles(startdir = ".", recursive = false, hidden = false)

Finds files from a given start directory and yields their names, similar to simple invocations of the command-line find utility. May be invoked in serial or non-zippered parallel contexts.

Arguments:
  • startdir : string – The root directory from which to start the search (defaults to ".")
  • recursive : bool – Indicates whether or not to descend recursively into subdirectories (defaults to false)
  • hidden : bool – Indicates whether or not to descend into hidden subdirectories and yield hidden files (defaults to false)
Yields:

The paths to any files found, relative to startdir, as strings
proc getGID(name: string): int

Obtains and returns the group id associated with the file or directory specified by name.

Will halt with an error message if one is detected

Arguments:name : string – The file or directory whose group id is desired
Returns:The group id of the file or directory in question
Return type:int
proc getMode(name: string): int

Obtains and returns the current permissions of the file or directory specified by name.

Will halt with an error message if one is detected

Arguments:name : string – The file or directory whose permissions are desired.
Returns:The permissions of the specified file or directory See description of S_IRUSR, for instance, for potential values.
Return type:int
proc getUID(name: string): int

Obtains and returns the user id associated with the file or directory specified by name.

Will halt with an error message if one is detected.

Arguments:name : string – The file or directory whose user id is desired
Returns:The user id of the specified file or directory
Return type:int
iter glob(pattern = "*")

Yields filenames that match a given glob pattern. May be invoked in serial or parallel contexts (zippered or non-).

Arguments:pattern : string – The glob pattern to match against (defaults to "*")
Yields:The matching filenames as strings
proc isDir(name: string): bool

Determine if the provided path name corresponds to a directory and return the result

Will halt with an error message if one is detected, including if the path does not refer to a valid file or directory

Arguments:name : string – A path that could refer to a directory.
Returns:true if the path is a directory, false if it is not
Return type:bool
proc isFile(name: string): bool

Determine if the provided path name corresponds to a file and return the result

Will halt with an error message if one is detected, including if the path does not refer to a valid file or directory

Arguments:name : string – A path that could refer to a file.
Returns:true if the path is a file, false if it is not
Return type:bool

Determine if the provided path name corresponds to a link and return the result. If symbolic links are not supported, will return false.

Will halt with an error message if one is detected, including if the path does not refer to a valid file or directory

Arguments:name : string – A path that could refer to a symbolic link.
Returns:true if the path is a symbolic link, false if it is not or if symbolic links are not supported.
Return type:bool
proc isMount(name: string): bool

Determine if the provided path name corresponds to a mount point and return the result.

Will halt with an error message if one is detected, including if the path does not refer to a valid file or directory.

Arguments:name : string – A path that could refer to a mount point.
Returns:true if the path is a mount point, false if it is not.
Return type:bool
iter listdir(path: string, hidden = false, dirs = true, files = true, listlinks = true): string

Lists the contents of a directory. May be invoked in serial contexts only.

Arguments:
  • path : string – The directory whose contents should be listed
  • hidden : bool – Indicates whether hidden files/directory should be listed (defaults to false)
  • dirs : bool – Indicates whether directories should be listed (defaults to true)
  • files : bool – Indicates whether files should be listed (defaults to true)
  • listlinks : bool – Indicates whether symbolic links should be listed (defaults to true)
Yields:

The names of the specified directory’s contents, as strings
proc mkdir(name: string, mode: int = 511, parents: bool = false)

Attempt to create a directory with the given path, name. If parents is true, will attempt to create any directory in the path that did not previously exist.

Will halt with an error message if one is detected

Warning

In the case where parents is true, there is a potential security vulnerability. Checking whether parent directories exist and creating them are separate events. This is called a Time of Check, Time of Use vulnerability (TOCTOU), and in the case of files or directories that did not previously exist, there is no known guard against it. So even if parents == true and a parent directory didn’t exist before this function was called but does exist afterward, it’s not necessarily true that this function created that parent. Some other concurrent operation could have done so, either intentionally or unintentionally, maliciously or ignorantly. This option is provided as a convenience only, and any attempt to perform the same functionality will run a similar risk.

Arguments:
  • name – The name of the directory to be created, fully specified.
  • mode – The permissions desired for the directory to create. Takes the current umask into account. See description of S_IRUSR, for instance, for potential values.
  • parents – Indicates whether parent directories should be created. If set to false, any nonexistent parent will cause an error to occur.
proc rename(oldname: string, newname: string)

Renames the file specified by oldname to newname. The file is not opened during this operation.

Will halt with an error message if one is detected

Arguments:
  • oldname : string – Current name of the file
  • newname : string – Name which should be used to refer to the file in the future.
proc remove(name: string)

Removes the file or directory specified by name

Will halt with an error message if one is detected

Arguments:name : string – The file/directory to remove
proc sameFile(file1: string, file2: string): bool

Determines if both pathnames refer to the same file or directory (utilizing operating system operations rather than string ones, due to the possibility of symbolic links, curDir, or parentDir appearing in the path) and returns the result of that check

Will halt with an error message if one is detected

Arguments:
  • file1 : string – The first path to be compared.
  • file2 : string – The second path to be compared.
Returns:

true if the two paths refer to the same file or directory, false otherwise.
Return type:

bool
proc sameFile(file1: file, file2: file): bool

Determines if both file records refer to the same file (utilizing operating system operations rather than string ones, due to the possibility of symbolic links, curDir, or parentDir appearing in the path) and returns the result of that check

Will halt with an error message if one is detected

Arguments:
  • file1 : file – The first file to be compared.
  • file2 : file – The second file to be compared.
Returns:

true if the two records refer to the same file, false otherwise.
Return type:

bool

Create a symbolic link pointing to oldName with the path newName.

Will halt with an error message if one is detected

Arguments:
  • oldName : string – The source file to be linked
  • newName : string – The location where the symbolic link should live
proc locale.umask(mask: int): int

Sets the file creation mask of the current locale to mask, and returns the previous value of the file creation mask for that locale. See description of S_IRUSR, for instance, for potential values.

Warning

This is not safe within a parallel context. A umask call in one task will affect the umask of all tasks for that locale.

Arguments:mask : int – The file creation mask to use now.
Returns:The previous file creation mask
Return type:int
iter walkdirs(path: string = ".", topdown = true, depth = max(int), hidden = false, followlinks = false, sort = false): string

Recursively walk a directory structure, yielding directory names. May be invoked in serial or non-zippered parallel contexts.

Note

The current parallel version is not very adaptive/dynamic in its application of parallelism to the list of subdirectories at any given level of the traversal, and could be improved in this regard.

Arguments:
  • path : string – The directory from which to start the walk (defaults to ".")
  • topdown : bool – Indicates whether to yield a directory before or after descending into its children (defaults to true)
  • depth : int – Indicates the maximum recursion depth to use (defaults to max(int))
  • hidden : bool – Indicates whether to descend into hidden directories (defaults to false)
  • followlinks : bool – Indicates whether to follow symbolic links (defaults to false)
  • sort : bool – Indicates whether or not to consider subdirectories in sorted order (defaults to false). Note that requesting sorting has no effect in parallel invocations.
Yields:

The directory names encountered, relative to path, as strings