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.\"
.IX Title "nbdkit-probing 1"
.TH nbdkit-probing 1 2024-04-21 nbdkit-1.38.1 NBDKIT
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH NAME
nbdkit\-probing \- how to probe for nbdkit configuration and plugins
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\& nbdkit \-\-dump\-config
.Ve
.PP
.Vb 1
\& nbdkit PLUGIN \-\-dump\-plugin
.Ve
.PP
.Vb 1
\& nbdkit \-\-version
.Ve
.PP
.Vb 1
\& nbdkit PLUGIN \-\-version
.Ve
.PP
.Vb 1
\& nbdkit \-\-filter=FILTER null \-\-version
.Ve
.PP
.Vb 1
\& nbdkit \-\-filter=FILTER null \-\-dump\-plugin
.Ve
.SH DESCRIPTION
.IX Header "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 are installed.
.SS "Query if nbdkit is installed"
.IX Subsection "Query if nbdkit is installed"
Use this command to see if the nbdkit program is installed:
.PP
.Vb 1
\& nbdkit \-\-version
.Ve
.PP
This will fail with an error and non-zero exit code if nbdkit is not
installed or not working.
.SS "Query basic configuration"
.IX Subsection "Query basic configuration"
.Vb 1
\& nbdkit \-\-dump\-config
.Ve
.PP
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:
.PP
.Vb 4
\& plugindir=/usr/lib64/nbdkit/plugins
\& version=1.20.1
\& version_major=1
\& version_minor=20
.Ve
.SS "Test nbdkit ≥ version"
.IX Subsection "Test nbdkit ≥ version"
To test if nbdkit ≥ a particular version is installed, use the
\&\fI\-\-dump\-config\fR option and look for the \f(CW\*(C`version_major\*(C'\fR and
\&\f(CW\*(C`version_minor\*(C'\fR fields:
.PP
.Vb 6
\& $ 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 \*(Aqnbdkit >= 1.12 is required\*(Aq; exit 1; fi
.Ve
.PP
These fields were first added in nbdkit 1.16.5 and were not present in
earlier versions.
.PP
You can also probe the minimum version using \fBpkg\-config\fR\|(1).  See
"PKG\-CONFIG/PKGCONF" in \fBnbdkit\-plugin\fR\|(3).
.SS "Query information about a particular plugin"
.IX Subsection "Query information about a particular plugin"
.Vb 1
\& nbdkit pluginname \-\-dump\-plugin
.Ve
.PP
(where \fIpluginname\fR is the name or full path of a plugin) will dump
information about that plugin, eg:
.PP
.Vb 8
\& $ 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]
.Ve
.PP
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 \f(CW\*(C`NBDKIT_API_VERSION\*(C'\fR of 2
fails to load with an older nbdkit that only knows
\&\f(CW\*(C`NBDKIT_API_VERSION\*(C'\fR 1).
.SS "Query information about a particular filter"
.IX Subsection "Query information about a particular filter"
You can use the \fI\-\-dump\-plugin\fR option to dump information about a
filter, by using the null plugin with the \fI\-\-filter\fR parameter:
.PP
.Vb 6
\& $ nbdkit null \-\-filter=qcow2dec \-\-dump\-plugin
\& [...]
\& qcow2dec_path=/usr/lib64/nbdkit/filters/nbdkit\-qcow2dec\-filter.so
\& qcow2dec_name=qcow2dec
\& qcow2dec_deflate=yes
\& qcow2dec_zstd=yes
.Ve
.SS "Detect if a plugin is installed"
.IX Subsection "Detect if a plugin is installed"
To find out if a plugin is installed (and working) in the plugin
directory, use:
.PP
.Vb 3
\& $ nbdkit foo \-\-version
\& nbdkit: error: cannot open plugin \*(Aqfoo\*(Aq: /usr/lib64/nbdkit/plugins/nbdkit\-foo\-plugin.so: cannot open shared object file: No such file or directory
\& Use \*(Aqnbdkit \-\-help\*(Aq or read the nbdkit(1) manual page for documentation.
.Ve
.PP
This will fail with an error and non-zero exit code if the \f(CW\*(C`foo\*(C'\fR
plugin cannot be loaded.
.PP
Note it is better to test for the existence of plugins this way rather
than just seeing if the \fI.so\fR file exists, because nbdkit will load
the plugin and check that all its dependencies can be satisfied, and
also that plugin registration works.
.SS "List all plugins in the plugin directory"
.IX Subsection "List all plugins in the plugin directory"
You could simply get the plugin directory (from \fI\-\-dump\-config\fR) and
list all files in this directory called \fInbdkit\-*\-plugin.so\fR.
.PP
However a better test is to run \fI\-\-dump\-plugin\fR (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:
.PP
.Vb 8
\& #!/bin/sh \-
\& plugindir=\`nbdkit \-\-dump\-config | grep ^plugindir= | sed \*(Aqs/[^=]*=//\*(Aq\`
\& for f in $plugindir/nbdkit\-*\-plugin.so; do
\&     if nbdkit "$f" \-\-version >/dev/null 2>&1; then
\&         b=\`echo "$f" | sed \*(Aqs,.*/nbdkit\-\e(.*\e)\-plugin.so$,\e1,\*(Aq\`
\&         echo "$b ($f)"
\&     fi
\& done
.Ve
.SS "Detect if a filter is installed"
.IX Subsection "Detect if a filter is installed"
To find out if a filter is installed (and working) use \fI\-\-version\fR
with the \f(CW\*(C`null\*(C'\fR plugin and the name of the filter to test:
.PP
.Vb 1
\& nbdkit \-\-version \-\-filter=foo null
.Ve
.PP
This will fail with an error and non-zero exit code if the \f(CW\*(C`foo\*(C'\fR
filter cannot be loaded.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBnbdkit\fR\|(1).
.SH AUTHORS
.IX Header "AUTHORS"
Eric Blake
.PP
Richard W.M. Jones
.PP
Pino Toscano
.SH COPYRIGHT
.IX Header "COPYRIGHT"
Copyright Red Hat
.SH LICENSE
.IX Header "LICENSE"
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
.IP \(bu 4
Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
.IP \(bu 4
Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
.IP \(bu 4
Neither the name of Red Hat nor the names of its contributors may be
used to endorse or promote products derived from this software without
specific prior written permission.
.PP
THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.