NAME

systemd-is-running - Check if systemd is running

VERSION

This document describes version 0.001 of systemd-is-running (from Perl distribution App-SystemdUtils), released on 2019-05-22.

SYNOPSIS

Usage:

% systemd-is-running [options]

DESCRIPTION

Will return payload of 1 if systemd is running, 0 if not running, undef if cannot determine for sure. The result metadata func.note will give more details. The following heuristics are currently used:

1. Check if /sbin/init exists, if it does not the return 0.

2. Check if /sbin/init is a symlink to something with /systemd/ in its name. If yes, then we return 1. We use Cwd's realpath() instead of readlink() here, to handle multiple redirection.

3. Check if /lib/systemd/systemd exists. Return 0 otherwise.

4. Check if /sbin/init is a hardlink to /lib/systemd/systemd by comparing its inode. Return 1 if it is.

5. Return undef otherwise, since we detect that /lib/systemd/systemd exists (systemd is installed) but we cannot be sure if it is running or not.

When used as a CLI, this routine will exit 0 if systemd is running, 1 if systemd is not running, or 99 if cannot determine for sure. To see the more detailed note, you can run the CLI with --json to return the whole enveloped response.

OPTIONS

* marks required options.

Output options

--format=s

Choose output format, e.g. json, text.

Default value:

undef

--json

Set output format to json.

--naked-res

When outputing as JSON, strip result envelope.

Default value:

0

By default, when outputing as JSON, the full enveloped result is returned, e.g.:

[200,"OK",[1,2,3],{"func.extra"=>4}]

The reason is so you can get the status (1st element), status message (2nd element) as well as result metadata/extra result (4th element) instead of just the result (3rd element). However, sometimes you want just the result, e.g. when you want to pipe the result for more post-processing. In this case you can use `--naked-res` so you just get:

[1,2,3]

Other options

--help, -h, -?

Display help message and exit.

--version, -v

Display program's version and exit.

COMPLETION

This script has shell tab completion capability with support for several shells.

bash

To activate bash completion for this script, put:

complete -C systemd-is-running systemd-is-running

in your bash startup (e.g. ~/.bashrc). Your next shell session will then recognize tab completion for the command. Or, you can also directly execute the line above in your shell to activate immediately.

It is recommended, however, that you install modules using cpanm-shcompgen which can activate shell completion for scripts immediately.

tcsh

To activate tcsh completion for this script, put:

complete systemd-is-running 'p/*/`systemd-is-running`/'

in your tcsh startup (e.g. ~/.tcshrc). Your next shell session will then recognize tab completion for the command. Or, you can also directly execute the line above in your shell to activate immediately.

It is also recommended to install shcompgen (see above).

other shells

For fish and zsh, install shcompgen as described above.

HOMEPAGE

Please visit the project's homepage at https://metacpan.org/release/App-SystemdUtils.

SOURCE

Source repository is at https://github.com/perlancar/perl-App-SystemdUtils.

BUGS

Please report any bugs or feature requests on the bugtracker website https://rt.cpan.org/Public/Dist/Display.html?Name=App-SystemdUtils

When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature.

AUTHOR

perlancar <perlancar@cpan.org>

COPYRIGHT AND LICENSE

This software is copyright (c) 2019 by perlancar@cpan.org.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

cpanm App::SystemdUtils

perl -MCPAN -e shell
install App::SystemdUtils