NAME

       nbdkit-probing - how to probe for nbdkit configuration and plugins

SYNOPSIS

        nbdkit --dump-config

        nbdkit PLUGIN --dump-plugin

        nbdkit --version

        nbdkit PLUGIN --version

        nbdkit --filter=FILTER null --version

DESCRIPTION

       You can query information about nbdkit and available plugins and filters using the nbdkit
       binary.  This can include whether nbdkit is installed, and whether plugins or filters and
       installed.

   Query if nbdkit is installed
       Use this command to see if the nbdkit program is installed:

        nbdkit --version

       This will fail with an error and non-zero exit code if nbdkit is not installed or not
       working.

   Query basic configuration
        nbdkit --dump-config

       lists information about how nbdkit was configured.  The most important fields in the
       output are the name of the directory where nbdkit looks for plugins and the version of
       nbdkit, eg:

        plugindir=/usr/lib64/nbdkit/plugins
        version=1.20.1
        version_major=1
        version_minor=20

   Test nbdkit ≥ version
       To test if nbdkit ≥ a particular version is installed, use the --dump-config option and
       look for the "version_major" and "version_minor" fields:

        $ nbdkit --dump-config | grep ^version_minor
        version_minor=20
        $ major=$( nbdkit --dump-config | grep ^version_major | cut -d= -f2 )
        $ minor=$( nbdkit --dump-config | grep ^version_minor | cut -d= -f2 )
        $ if [ $major -eq 1 ] && [ $minor -lt 12 ]
          then echo 'nbdkit >= 1.12 is required'; exit 1; fi

       These fields were first added in nbdkit 1.16.5 and were not present in earlier versions.

       You can also probe the minimum version using pkg-config(1).  See "PKG-CONFIG/PKGCONF" in
       nbdkit-plugin(3).

   Query information about a particular plugin
        nbdkit pluginname --dump-plugin

       (where pluginname is the name or full path of a plugin) will dump information about that
       plugin, eg:

        $ nbdkit file --dump-plugin
        path=/usr/lib64/nbdkit/plugins/nbdkit-file-plugin.so
        name=file
        version=1.20.1
        api_version=1
        struct_size=176
        thread_model=serialize_requests
        [etc]

       Plugins which ship with nbdkit usually have the same version as the corresponding nbdkit
       binary.  The nbdkit binary will always be able to utilize plugins compiled against an
       older version of the header; however, newer plugins may not be fully supported by an older
       nbdkit binary (for example, a plugin compiled with "NBDKIT_API_VERSION" of 2 fails to load
       with an older nbdkit that only knows "NBDKIT_API_VERSION" 1).

   Detect if a plugin is installed
       To find out if a plugin is installed (and working) in the plugin directory, use:

        $ nbdkit foo --version
        nbdkit: error: cannot open plugin 'foo': /usr/lib64/nbdkit/plugins/nbdkit-foo-plugin.so: cannot open shared object file: No such file or directory
        Use 'nbdkit --help' or read the nbdkit(1) manual page for documentation.

       This will fail with an error and non-zero exit code if the "foo" plugin cannot be loaded.

       Note it is better to test for the existence of plugins this way rather than just seeing if
       the .so file exists, because nbdkit will load the plugin and check that all its
       dependencies can be satisfied, and also that plugin registration works.

   List all plugins in the plugin directory
       You could simply get the plugin directory (from --dump-config) and list all files in this
       directory called nbdkit-*-plugin.so.

       However a better test is to run --dump-plugin (see above) on each one to check that it is
       working and all of its dependencies are installed.  A complete shell script which does
       this is:

        #!/bin/sh -
        plugindir=`nbdkit --dump-config | grep ^plugindir= | sed 's/[^=]*=//'`
        for f in $plugindir/nbdkit-*-plugin.so; do
            if nbdkit "$f" --version >/dev/null 2>&1; then
                b=`echo "$f" | sed 's,.*/nbdkit-\(.*\)-plugin.so$,\1,'`
                echo "$b ($f)"
            fi
        done

   Detect if a filter is installed
       To find out if a filter is installed (and working) use --version with the "null" plugin
       and the name of the filter to test:

        nbdkit --version --filter=foo null

       This will fail with an error and non-zero exit code if the "foo" filter cannot be loaded.

SEE ALSO

       nbdkit(1).

AUTHORS

       Eric Blake

       Richard W.M. Jones

       Pino Toscano

COPYRIGHT

       Copyright (C) 2013-2020 Red Hat Inc.

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