Nasal library/os.path

This page contains documentation for the os.path namespace in Nasal. This namespace implements tools (from SGPath) for manipulating file paths. Everything in the os.path namespace is sourced from flightgear/src/Scripting/NasalSGPath.cxx

Tip  Copy & paste the examples into your Nasal Console and execute them to see what they do.

Note  Everything here was added to FlightGear 3.0. (released February 2014)

Class

os.path

A pseudo-class (actually a Nasal ghost). This is the main class that stores and allows manipulation of file paths. This is also integrated into the os.path.

new()

os.path.new([path]);

Constructor function. Returns a new os.path instance. Note that the path must not violate the rules for allowed paths.

path

Optional string specifying the filepath. If not given, the path will default to $FG_ROOT

Example

var path = os.path.new("C:/Windows"); # Windows filepath
# var path = os.path.new("/usr/bin/"); # Unix filepath
print(path.realpath);

set()

os.path.set([path]);

Sets the filepath. Note that the path must not violate the rules for allowed paths.

path

Optional string specifying the filepath. If not given, the path will be set to $FG_ROOT

Example

var path = os.path.new("C:/Windows");
# var path = os.path.new("/usr/bin/"); # alternative Unix filepath
print(path.realpath);
path.set("C:/Windows/Program Files");
# path.set("/usr/"); # alternative Unix filepath
print(path.realpath); # prints new path

append()

os.path.append([path]);

Appends a new part to the filepath.

path

Optional string specifying the new part to add to the filepath. If not given, the resultant path will not change.

Example

var path = os.path.new("C:/Windows");
# var path = os.path.new("/usr/"); # alternative Unix filepath
print(path.realpath);
path.append("Program Files");
# path.append("bin"); # alternative Unix filepath
print(path.realpath); # prints "C:/Windows/Program Files" or "/usr/bin"

concat()

os.path.concat([path]);

Appends a new part to the filepath.

path

Optional string specifying part to concat to the existing filepath. Note that this will simply add the string to the end of the path without adding a separator. If not given, the resultant path will not change.

Example

var path = os.path.new("C:/Windows");
# var path = os.path.new("/usr"); # alternative Unix filepath
print(path.realpath);
path.concat("/Program Files");
# path.concat("/bin"); # alternative Unix filepath
print(path.realpath); # prints "C:/Windows/Program Files" or "/usr/bin"

exists()

os.path.exists();

Returns 1 (true) if the path exists and 0 (false) if it does not.

Example

var path = os.path.new("C:/Windows");
# var path = os.path.new("/usr"); # alternative Unix filepath
print(path.exists()); # prints 1 (true)
path.set("C:/Window");
# path.set("/r"); # alternative Unix filepath
print(path.exists()); # prints 0 (false)

canRead()

os.path.canRead();

Returns 1 (true) if the path can be read (from Nasal) and 0 (false) if it cannot. This follows the rules for allowed paths.

Example

var path = os.path.new("C:/Windows");
# var path = os.path.new("/usr"); # alternative Unix filepath
print(path.canRead()); # prints 0 (false)
path.set(getprop("sim/fg-home"));
print(path.canRead()); # prints 1 (true)

canWrite()

os.path.canWrite();

Returns 1 (true) if the path can be written to (from Nasal) and 0 (false) if it cannot. This follows the rules for allowed paths.

Example

var path = os.path.new("C:/Windows");
# var path = os.path.new("/usr"); # alternative Unix filepath
print(path.canWrite()); # prints 0 (false)
path.set(getprop("sim/fg-home") ~ "/txt.log");
print(path.canWrite()); # prints 1 (true)

isFile()

os.path.isFile();

Returns 1 (true) if the path points to a file and 0 (false) if it points to a directory. Note that the path must also exist.

Example

var path = os.path.new(getprop("sim/fg-root"));
print(path.isFile()); # prints 0 (false)
path.append("Nasal/io.nas");
print(path.isFile()); # prints 1 (true)

isDir()

os.path.isDir();

Returns 1 (true) if the path points to a directory and 0 (false) if it points to a file. Note that the path must also exist.

Example

var path = os.path.new(getprop("sim/fg-root"));
print(path.isDir()); # prints 1 (true)
path.append("Nasal/io.nas");
print(path.isDir()); # prints 0 (false)

isRelative()

os.path.isRelative();

Returns 1 (true) if the path is relative and 0 (false) if it is not.

Example

var path = os.path.new(getprop("sim/fg-root"));
path.set("./Nasal");
print(path.isRelative()); # prints 1 (true)

isAbsolute()

os.path.isAbsolute();

Returns 1 (true) if the path is an absolute path and 0 (false) if it is not.

Example

var path = os.path.new(getprop("sim/fg-root"));
print(path.isAbsolute()); # prints 1 (true)

isNull()

os.path.isNull();

Returns 1 (true) if the path is null and 0 (false) if it is not.

Example

var path = os.path.new();
print(path.isNull());

create_dir()

os.path.create_dir();

Creates the parent of the path as a directory. This will only work if the path is absolute and considered as writable by fgValidatePath() (typically okay under $FG_HOME/Export).

Example

var path = os.path.new(getprop("/sim/fg-home") ~ "/Export/test/demo.txt");
path.create_dir(); # Creates $FG_HOME/Export/test/

remove()

os.path.remove();

Removes the last element of the path from the file directory. This will only work if the path is absolute and deletion of the file is permitted by the file permissions (typically okay under $FG_HOME/Export). Note that on Windows, deletion of read-only files are never permitted.

Examples

var path = os.path.new(getprop("/sim/fg-home") ~ "/Export/demo.txt");
var file = io.open(path.realpath, "w");
io.write(file, 'Hello, World' ~ "\n");
io.close(file);
print(path.exists()); # prints "1"

path.remove();
print(path.exists()); # prints "0"

var path = os.path.new(getprop("/sim/fg-home") ~ "/Export/test");
path.create_dir();
path.remove(); # folder "/test" is removed

rename()

os.path.rename(new_name);

Renames the last element of the path from the file directory. This will only work if the path is absolute, the old path is both readable and writable, the new path is writable.

Example

var path = os.path.new(getprop("/sim/fg-home") ~ "/Export/demo.txt");
var file = io.open(path.realpath, "w");
io.write(file, 'Hello, World' ~ "\n");
io.close(file);
path.rename(getprop("/sim/fg-home") ~ "/Export/demo1.txt");
print(path.realpath); # prints $FG_HOME/Export/demo1.txt

realpath

os.path.realpath;

A string variable that gives the full file path. This should only be used when the path is an absolute path. If the path is relative, it will simply be appended to the FlightGear folder (the level up from $FG_ROOT).

Example

var path = os.path.new(getprop("/sim/fg-home"));
print(path.realpath); # prints the absolute path of $FG_HOME

file

os.path.file;

A string variable that gives the last part of the filepath.

Example

var path = os.path.new(getprop("/sim/fg-home"));
print(path.file); # prints "flightgear.org"

dir

os.path.dir;

A string variable that gives all of the filepath except the last element (see os.path.file above).

Example

var path = os.path.new("Program Files/temp/text.txt");
print(path.dir); # prints "Program Files/temp"

base

os.path.base;

A string variable that gives all of the filepath except the extension of the file. If the filepath points to a folder, it has the same value as realpath.

Example

var path = os.path.new("Program Files/temp/text.txt");
print(path.base); # prints "Program Files/temp/text"

file_base

os.path.file_base;

A string variable that gives the file name without the extension. If the filepath points to a folder, it will simply be the folder name.

Example

var path = os.path.new("Program Files/temp/text.txt");
print(path.file_base); # prints "text"

extension

os.path.extension;

A string variable that gives the file's extension. If the filepath points to a folder, it will be an empty string.

Example

var path = os.path.new("Program Files/temp/text.txt");
print(path.extension); # prints "txt"

lower_extension

os.path.lower_extension;

A string variable that gives the file's extension, but converted to lowercase. If the filepath points to a folder, it will be an empty string.

Example

var path = os.path.new("Program Files/temp/text.TXT");
print(path.lower_extension); # prints "txt"

complete_lower_extension

os.path.complete_lower_extension;

This is to be used when a file has a double extension (e.g., .tar.gz). It also converts it to lowercase. If the filepath points to a folder, it will be an empty string.

Example

var path = os.path.new("Program Files/temp/text.TAR.GZ");
print(path.complete_lower_extension); # prints "tar.gz"

str

os.path.str;

A string giving the path that the instance points too. This is to be used when a file has a double extension (e.g., .tar.gz). It also converts it to lowercase. If the filepath points to a folder, it will be an empty string.

Examples

var path = os.path.new("../temp/text.txt");
print(path.str); # prints "../temp/text.txt"

var path = os.path.new(getprop("sim/fg-home"));
print(path.str); # prints the full path to $FG_HOME

mtime

os.path.mtime;

An integer giving the Unix time when the file or folder was last modified.

Example

var path = os.path.new(getprop("sim/fg-home"));
print(path.mtime); # prints a Unix time

Functions

desktop()

os.path.desktop();

Creates and returns an os.path pointing to the desktop location.

Note  As of April 2018, this function does not work properly and returns the /bin folder.

Example

var path = os.path.desktop();
print(path.realpath);

standardLocation()

os.path.standardLocation(location);

Creates and returns an os.path pointing to the standard location.

Note  As of April 2018, only supplying "HOME" to this function actually works. All the others do not work properly and return the /bin folder.

location

String specifying the standard location to use. May be one of HOME, DESKTOP, DOWNLOADS, DOCUMENTS, or PICTURES.

Example

var path = os.path.standardLocation("HOME");
print(path.realpath);