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### 38.1 Installing and Removing Packages

Assuming a package is available in the file `image-1.0.0.tar.gz` it can be installed from the Octave prompt with the command

    pkg install image-1.0.0.tar.gz

If the package is installed successfully nothing will be printed on the prompt, but if an error occurred during installation it will be reported. It is possible to install several packages at once by writing several package files after the `pkg install` command. If a different version of the package is already installed it will be removed prior to installing the new package. This makes it easy to upgrade and downgrade the version of a package, but makes it impossible to have several versions of the same package installed at once.

To see which packages are installed type

    pkg list
    -| Package Name  | Version | Installation directory
    -| --------------+---------+-----------------------
    -|        image *|   1.0.0 | /home/jwe/octave/image-1.0.0

In this case only version 1.0.0 of the `image` package is installed. The `'*'` character next to the package name shows that the image package is loaded and ready for use.

It is possible to remove a package from the system using the `pkg uninstall` command like this

    pkg uninstall image

If the package is removed successfully nothing will be printed in the prompt, but if an error occurred it will be reported. It should be noted that the package file used for installation is not needed for removal, and that only the package name as reported by `pkg list` should be used when removing a package. It is possible to remove several packages at once by writing several package names after the `pkg uninstall` command.

To minimize the amount of code duplication between packages it is possible that one package depends on another one. If a package depends on another, it will check if that package is installed during installation. If it is not, an error will be reported and the package will not be installed. This behavior can be disabled by passing the `-nodeps` flag to the `pkg install` command

    pkg install -nodeps my_package_with_dependencies.tar.gz

Since the installed package expects its dependencies to be installed it may not function correctly. Because of this it is not recommended to disable dependency checking.

Command: pkg command pkg_name
Command: pkg command option pkg_name

  Manage packages (groups of add-on functions) for Octave. Different actions are available depending on the value of command.

  Available commands:

  ‘`install`’

    Install named packages. For example,

        pkg install image-1.0.0.tar.gz

    installs the package found in the file `image-1.0.0.tar.gz`.

    The option variable can contain options that affect the manner in which a package is installed. These options can be one or more of

    `-nodeps`

      The package manager will disable dependency checking. With this option it is possible to install a package even when it depends on another package which is not installed on the system. Use this option with care.

    `-noauto`

      The package manager will not automatically load the installed package when starting Octave. This overrides any setting within the package.

    `-auto`

      The package manager will automatically load the installed package when starting Octave. This overrides any setting within the package.

    `-local`

      A local installation (package available only to current user) is forced, even if the user has system privileges.

    `-global`

      A global installation (package available to all users) is forced, even if the user doesn’t normally have system privileges.

    `-forge`

      Install a package directly from the Octave-Forge repository. This requires an internet connection and the cURL library.

    `-verbose`

      The package manager will print the output of all commands as they are performed.

  ‘`update`’

    Check installed Octave-Forge packages against repository and update any outdated items. This requires an internet connection and the cURL library. Usage:

        pkg update

  ‘`uninstall`’

    Uninstall named packages. For example,

        pkg uninstall image

    removes the `image` package from the system. If another installed package depends on the `image` package an error will be issued. The package can be uninstalled anyway by using the `-nodeps` option.

  ‘`load`’

    Add named packages to the path. After loading a package it is possible to use the functions provided by the package. For example,

        pkg load image

    adds the `image` package to the path. It is possible to load all installed packages at once with the keyword ‘`all`’. Usage:

        pkg load all

  ‘`unload`’

    Remove named packages from the path. After unloading a package it is no longer possible to use the functions provided by the package. It is possible to unload all installed packages at once with the keyword ‘`all`’. Usage:

        pkg unload all

  ‘`list`’

    Show the list of currently installed packages. For example,

        installed_packages = pkg ("list")

    returns a cell array containing a structure for each installed package.

    If two output arguments are requested `pkg` splits the list of installed packages into those which were installed by the current user, and those which were installed by the system administrator.

        [user_packages, system_packages] = pkg ("list")

    The option `"-forge"` lists packages available at the Octave-Forge repository. This requires an internet connection and the cURL library. For example:

        oct_forge_pkgs = pkg ("list", "-forge")

  ‘`describe`’

    Show a short description of the named installed packages, with the option `"-verbose"` also list functions provided by the package. For example,

        pkg describe -verbose all

    will describe all installed packages and the functions they provide. If one output is requested a cell of structure containing the description and list of functions of each package is returned as output rather than printed on screen:

        desc = pkg ("describe", "secs1d", "image")

    If any of the requested packages is not installed, pkg returns an error, unless a second output is requested:

        [desc, flag] = pkg ("describe", "secs1d", "image")

    flag will take one of the values `"Not installed"`, `"Loaded"`, or `"Not loaded"` for each of the named packages.

  ‘`prefix`’

    Set the installation prefix directory. For example,

        pkg prefix ~/my_octave_packages

    sets the installation prefix to `~/my_octave_packages`. Packages will be installed in this directory.

    It is possible to get the current installation prefix by requesting an output argument. For example:

        pfx = pkg ("prefix")

    The location in which to install the architecture dependent files can be independently specified with an addition argument. For example:

        pkg prefix ~/my_octave_packages ~/my_arch_dep_pkgs

  ‘`local_list`’

    Set the file in which to look for information on locally installed packages. Locally installed packages are those that are available only to the current user. For example:

        pkg local_list ~/.octave_packages

    It is possible to get the current value of local_list with the following

        pkg local_list

  ‘`global_list`’

    Set the file in which to look for information on globally installed packages. Globally installed packages are those that are available to all users. For example:

        pkg global_list /usr/share/octave/octave_packages

    It is possible to get the current value of global_list with the following

        pkg global_list

  ‘`build`’

    Build a binary form of a package or packages. The binary file produced will itself be an Octave package that can be installed normally with `pkg`. The form of the command to build a binary package is

        pkg build builddir image-1.0.0.tar.gz …

    where `builddir` is the name of a directory where the temporary installation will be produced and the binary packages will be found. The options `-verbose` and `-nodeps` are respected, while all other options are ignored.

  ‘`rebuild`’

    Rebuild the package database from the installed directories. This can be used in cases where the package database has been corrupted. It can also take the `-auto` and `-noauto` options to allow the autoloading state of a package to be changed. For example,

        pkg rebuild -noauto image

    will remove the autoloading status of the image package.

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