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<h3><a href="../contents.html">Table Of Contents</a></h3>
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<li><a class="reference internal" href="#">grp – Unix Group Database</a><ul>
<li><a class="reference internal" href="#querying-all-groups">Querying All Groups</a></li>
<li><a class="reference internal" href="#group-memberships-for-a-user">Group Memberships for a User</a></li>
<li><a class="reference internal" href="#finding-a-group-by-name">Finding a Group By Name</a></li>
<li><a class="reference internal" href="#finding-a-group-by-id">Finding a Group by ID</a></li>
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<div class="section" id="module-grp">
<span id="grp-unix-group-database"></span><h1>grp – Unix Group Database<a class="headerlink" href="#module-grp" title="Permalink to this headline">¶</a></h1>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Purpose:</th><td class="field-body">Read group data from Unix group database.</td>
</tr>
<tr class="field"><th class="field-name">Python Version:</th><td class="field-body">1.4 and later</td>
</tr>
</tbody>
</table>
<p>The grp module can be used to read information about Unix groups from
the group database (usually <tt class="docutils literal"><span class="pre">/etc/group</span></tt>). The read-only interface
returns tuple-like objects with named attributes for the standard
fields of a group record.</p>
<table border="1" class="docutils">
<colgroup>
<col width="12%" />
<col width="21%" />
<col width="67%" />
</colgroup>
<thead valign="bottom">
<tr><th class="head">Index</th>
<th class="head">Attribute</th>
<th class="head">Meaning</th>
</tr>
</thead>
<tbody valign="top">
<tr><td>0</td>
<td>gr_name</td>
<td>Name</td>
</tr>
<tr><td>1</td>
<td>gr_passwd</td>
<td>Password, if any (encrypted)</td>
</tr>
<tr><td>2</td>
<td>gr_gid</td>
<td>Numerical id (integer)</td>
</tr>
<tr><td>3</td>
<td>gr_mem</td>
<td>Names of group members</td>
</tr>
</tbody>
</table>
<p>The name and password values are both strings, the GID is an integer,
and the members are reported as a list of strings.</p>
<div class="section" id="querying-all-groups">
<h2>Querying All Groups<a class="headerlink" href="#querying-all-groups" title="Permalink to this headline">¶</a></h2>
<p>Suppose you need to print a report of all of the “real” groups on a
system, including their members (for our purposes, “real” is defined
as having a name not starting with “<tt class="docutils literal"><span class="pre">_</span></tt>”). To load the entire
password database, you would use <tt class="docutils literal"><span class="pre">getgrall()</span></tt>. The return value is
a list with an undefined order, so you probably want to sort it before
printing the report.</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">grp</span>
<span class="kn">import</span> <span class="nn">operator</span>
<span class="c"># Load all of the user data, sorted by username</span>
<span class="n">all_groups</span> <span class="o">=</span> <span class="n">grp</span><span class="o">.</span><span class="n">getgrall</span><span class="p">()</span>
<span class="n">interesting_groups</span> <span class="o">=</span> <span class="nb">sorted</span><span class="p">((</span><span class="n">g</span>
<span class="k">for</span> <span class="n">g</span> <span class="ow">in</span> <span class="n">all_groups</span>
<span class="k">if</span> <span class="ow">not</span> <span class="n">g</span><span class="o">.</span><span class="n">gr_name</span><span class="o">.</span><span class="n">startswith</span><span class="p">(</span><span class="s">'_'</span><span class="p">)),</span>
<span class="n">key</span><span class="o">=</span><span class="n">operator</span><span class="o">.</span><span class="n">attrgetter</span><span class="p">(</span><span class="s">'gr_name'</span><span class="p">))</span>
<span class="c"># Find the longest length for the name</span>
<span class="n">name_length</span> <span class="o">=</span> <span class="nb">max</span><span class="p">(</span><span class="nb">len</span><span class="p">(</span><span class="n">g</span><span class="o">.</span><span class="n">gr_name</span><span class="p">)</span> <span class="k">for</span> <span class="n">g</span> <span class="ow">in</span> <span class="n">interesting_groups</span><span class="p">)</span> <span class="o">+</span> <span class="mi">1</span>
<span class="c"># Print report headers</span>
<span class="n">fmt</span> <span class="o">=</span> <span class="s">'</span><span class="si">%-*s</span><span class="s"> </span><span class="si">%4s</span><span class="s"> </span><span class="si">%10s</span><span class="s"> </span><span class="si">%s</span><span class="s">'</span>
<span class="k">print</span> <span class="n">fmt</span> <span class="o">%</span> <span class="p">(</span><span class="n">name_length</span><span class="p">,</span> <span class="s">'Name'</span><span class="p">,</span>
<span class="s">'GID'</span><span class="p">,</span>
<span class="s">'Password'</span><span class="p">,</span>
<span class="s">'Members'</span><span class="p">)</span>
<span class="k">print</span> <span class="s">'-'</span> <span class="o">*</span> <span class="n">name_length</span><span class="p">,</span> <span class="s">'----'</span><span class="p">,</span> <span class="s">'-'</span> <span class="o">*</span> <span class="mi">10</span><span class="p">,</span> <span class="s">'-'</span> <span class="o">*</span> <span class="mi">30</span>
<span class="c"># Print the data</span>
<span class="k">for</span> <span class="n">g</span> <span class="ow">in</span> <span class="n">interesting_groups</span><span class="p">:</span>
<span class="k">print</span> <span class="n">fmt</span> <span class="o">%</span> <span class="p">(</span><span class="n">name_length</span><span class="p">,</span> <span class="n">g</span><span class="o">.</span><span class="n">gr_name</span><span class="p">,</span>
<span class="n">g</span><span class="o">.</span><span class="n">gr_gid</span><span class="p">,</span>
<span class="n">g</span><span class="o">.</span><span class="n">gr_passwd</span><span class="p">,</span>
<span class="s">', '</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">g</span><span class="o">.</span><span class="n">gr_mem</span><span class="p">))</span>
</pre></div>
</div>
<div class="highlight-python"><pre>$ python grp_getgrall.py
Name GID Password Members
---------------------------------------- ---- ---------- ------------------------------
accessibility 90 *
admin 80 * root, dhellmann
authedusers 50 *
bin 7 *
certusers 29 * root, _jabber, _postfix, _cyrus, _calendar, _dovecot
com.apple.access_screensharing-disabled 101 dhellmann
com.apple.access_ssh 102 dhellmann
consoleusers 53 *
daemon 1 * root
dhellmann 501
dialer 68 *
everyone 12 *
group 16 *
interactusers 51 *
kmem 2 * root
localaccounts 61 *
mail 6 * _teamsserver
netaccounts 62 *
netusers 52 *
network 69 *
nobody 4294967294 *
nogroup 4294967295 *
operator 5 * root
owner 10 *
postgres 401
procmod 9 * root
procview 8 * root
racemi 500 dhellmann
smmsp 25 *
staff 20 * root
sys 3 * root
tty 4 * root
utmp 45 *
wheel 0 * root</pre>
</div>
</div>
<div class="section" id="group-memberships-for-a-user">
<h2>Group Memberships for a User<a class="headerlink" href="#group-memberships-for-a-user" title="Permalink to this headline">¶</a></h2>
<p>Another common task might be to print a list of all the groups for a
given user:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">grp</span>
<span class="n">username</span> <span class="o">=</span> <span class="s">'dhellmann'</span>
<span class="n">groups</span> <span class="o">=</span> <span class="p">[</span><span class="n">g</span><span class="o">.</span><span class="n">gr_name</span> <span class="k">for</span> <span class="n">g</span> <span class="ow">in</span> <span class="n">grp</span><span class="o">.</span><span class="n">getgrall</span><span class="p">()</span> <span class="k">if</span> <span class="n">username</span> <span class="ow">in</span> <span class="n">g</span><span class="o">.</span><span class="n">gr_mem</span><span class="p">]</span>
<span class="k">print</span> <span class="n">username</span><span class="p">,</span> <span class="s">'belongs to:'</span><span class="p">,</span> <span class="s">', '</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">groups</span><span class="p">)</span>
</pre></div>
</div>
<div class="highlight-python"><pre>$ python grp_groups_for_user.py
dhellmann belongs to: _lpadmin, admin, com.apple.access_screensharing-disabled, com.apple.access_ssh, racemi</pre>
</div>
</div>
<div class="section" id="finding-a-group-by-name">
<h2>Finding a Group By Name<a class="headerlink" href="#finding-a-group-by-name" title="Permalink to this headline">¶</a></h2>
<p>As with <a class="reference internal" href="../pwd/index.html#module-pwd" title="pwd: Unix Password Database"><tt class="xref py py-mod docutils literal"><span class="pre">pwd</span></tt></a>, it is also possible to query for information about
a specific group, either by name or numeric id.</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">grp</span>
<span class="n">name</span> <span class="o">=</span> <span class="s">'admin'</span>
<span class="n">info</span> <span class="o">=</span> <span class="n">grp</span><span class="o">.</span><span class="n">getgrnam</span><span class="p">(</span><span class="n">name</span><span class="p">)</span>
<span class="k">print</span> <span class="s">'Name :'</span><span class="p">,</span> <span class="n">info</span><span class="o">.</span><span class="n">gr_name</span>
<span class="k">print</span> <span class="s">'GID :'</span><span class="p">,</span> <span class="n">info</span><span class="o">.</span><span class="n">gr_gid</span>
<span class="k">print</span> <span class="s">'Password:'</span><span class="p">,</span> <span class="n">info</span><span class="o">.</span><span class="n">gr_passwd</span>
<span class="k">print</span> <span class="s">'Members :'</span><span class="p">,</span> <span class="s">', '</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">info</span><span class="o">.</span><span class="n">gr_mem</span><span class="p">)</span>
</pre></div>
</div>
<div class="highlight-python"><pre>$ python grp_getgrnam.py
Name : admin
GID : 80
Password: *
Members : root, dhellmann</pre>
</div>
</div>
<div class="section" id="finding-a-group-by-id">
<h2>Finding a Group by ID<a class="headerlink" href="#finding-a-group-by-id" title="Permalink to this headline">¶</a></h2>
<p>To identify the group running the current process, combine
<tt class="docutils literal"><span class="pre">getgrgid()</span></tt> with <tt class="docutils literal"><span class="pre">os.getgid()</span></tt>.</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">grp</span>
<span class="kn">import</span> <span class="nn">os</span>
<span class="n">gid</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">getgid</span><span class="p">()</span>
<span class="n">group_info</span> <span class="o">=</span> <span class="n">grp</span><span class="o">.</span><span class="n">getgrgid</span><span class="p">(</span><span class="n">gid</span><span class="p">)</span>
<span class="k">print</span> <span class="s">'Currently running with GID=</span><span class="si">%s</span><span class="s"> name=</span><span class="si">%s</span><span class="s">'</span> <span class="o">%</span> <span class="p">(</span><span class="n">gid</span><span class="p">,</span> <span class="n">group_info</span><span class="o">.</span><span class="n">gr_name</span><span class="p">)</span>
</pre></div>
</div>
<div class="highlight-python"><pre>$ python grp_getgrgid_process.py
Currently running with GID=501 name=dhellmann</pre>
</div>
<p>And to get the group name based on the permissions on a file, look up
the group returned by <tt class="docutils literal"><span class="pre">os.stat()</span></tt>.</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">grp</span>
<span class="kn">import</span> <span class="nn">os</span>
<span class="kn">import</span> <span class="nn">sys</span>
<span class="n">filename</span> <span class="o">=</span> <span class="s">'grp_getgrgid_fileowner.py'</span>
<span class="n">stat_info</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">stat</span><span class="p">(</span><span class="n">filename</span><span class="p">)</span>
<span class="n">owner</span> <span class="o">=</span> <span class="n">grp</span><span class="o">.</span><span class="n">getgrgid</span><span class="p">(</span><span class="n">stat_info</span><span class="o">.</span><span class="n">st_gid</span><span class="p">)</span><span class="o">.</span><span class="n">gr_name</span>
<span class="k">print</span> <span class="s">'</span><span class="si">%s</span><span class="s"> is owned by </span><span class="si">%s</span><span class="s"> (</span><span class="si">%s</span><span class="s">)'</span> <span class="o">%</span> <span class="p">(</span><span class="n">filename</span><span class="p">,</span> <span class="n">owner</span><span class="p">,</span> <span class="n">stat_info</span><span class="o">.</span><span class="n">st_gid</span><span class="p">)</span>
</pre></div>
</div>
<div class="highlight-python"><pre>$ python grp_getgrgid_fileowner.py
grp_getgrgid_fileowner.py is owned by dhellmann (501)</pre>
</div>
<div class="admonition-see-also admonition seealso">
<p class="first admonition-title">See also</p>
<dl class="last docutils">
<dt><a class="reference external" href="http://docs.python.org/library/grp.html">grp</a></dt>
<dd>The standard library documentation for this module.</dd>
<dt><a class="reference internal" href="../pwd/index.html#module-pwd" title="pwd: Unix Password Database"><tt class="xref py py-mod docutils literal"><span class="pre">pwd</span></tt></a></dt>
<dd>Read user data from the password database.</dd>
<dt><tt class="xref py py-mod docutils literal"><span class="pre">spwd</span></tt></dt>
<dd>Read user data from the shadow password database.</dd>
</dl>
</div>
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