File: node36.html

package info (click to toggle)
rutebook 1.0-1
links: PTS
area: non-free
in suites: sarge
size: 9,476 kB
ctags: 1,112
sloc: makefile: 47
file content (463 lines) | stat: -rw-r--r-- 18,904 bytes
parent folder | download | duplicates (2)
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">

<!--Converted with LaTeX2HTML 99.2beta8 (1.46)
original version by:  Nikos Drakos, CBLU, University of Leeds
* revised and updated by:  Marcus Hennecke, Ross Moore, Herb Swan
* with significant contributions from:
  Jens Lippmann, Marek Rouchal, Martin Wilck and others -->
<HTML>
<HEAD>
<TITLE>33. Sending Faxes</TITLE>
<META NAME="description" CONTENT="33. Sending Faxes">
<META NAME="keywords" CONTENT="rute">
<META NAME="resource-type" CONTENT="document">
<META NAME="distribution" CONTENT="global">

<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1">
<META NAME="Generator" CONTENT="LaTeX2HTML v99.2beta8">
<META HTTP-EQUIV="Content-Style-Type" CONTENT="text/css">

<LINK REL="STYLESHEET" HREF="rute.css">

<LINK REL="next" HREF="node37.html">
<LINK REL="previous" HREF="node35.html">
<LINK REL="up" HREF="rute.html">
<LINK REL="next" HREF="node37.html">
</HEAD>

<BODY BGCOLOR=#FFFFFF >
<TABLE width="100%" border="0" cellspacing="0" cellpadding="0">
<TR><TD align=left bgcolor="#000000">
<FONT COLOR=white>
&nbsp;<A HREF="http://www.icon.co.za/~psheer/rute-purchase.html"><FONT COLOR=white>Purchase</FONT></A>&nbsp;
</FONT>
</TD><TD align=center bgcolor="#000000">
<FONT COLOR=white>
Copyright&nbsp;&#169;&nbsp;2002&nbsp;Paul Sheer. <A HREF="copying.html"><FONT COLOR=white>Click here for copying permissions.</FONT></A>
</FONT>
</TD><TD align=right bgcolor="#000000">
<FONT COLOR=white>
&nbsp;<A HREF="http://www.icon.co.za/~psheer/rute-home.html"><FONT COLOR=white>Home</FONT></A>&nbsp;
</FONT>
</TD></TR>
<TR><TD colspan=2 align=left bgcolor="#ECEBF4">
<IMG SRC="va-btn-small-light-60.png">
</TD><TD align=right bgcolor="#ECEBF4">
<IMG SRC="sflogo2-steel-60.png">
</TD></TR>
</TABLE><BR>

<!--Navigation Panel-->
<A NAME="tex2html2456"
  HREF="node37.html">
<IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="next.png"></A> 
<A NAME="tex2html2452"
  HREF="rute.html">
<IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="up.png"></A> 
<A NAME="tex2html2446"
  HREF="node35.html">
<IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="prev.png"></A> 
<A NAME="tex2html2454"
  HREF="node1.html">
<IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents" SRC="contents.png"></A>  
<BR>
<B> Next:</B> <A NAME="tex2html2457"
  HREF="node37.html">34. uucp and uux</A>
<B> Up:</B> <A NAME="tex2html2453"
  HREF="rute.html">rute</A>
<B> Previous:</B> <A NAME="tex2html2447"
  HREF="node35.html">32. init, ? getty,</A>
 &nbsp <B>  <A NAME="tex2html2455"
  HREF="node1.html">Contents</A></B> 
<BR>
<BR>
<!--End of Navigation Panel-->
<!--Table of Child-Links-->
<A NAME="CHILD_LINKS"><STRONG>Subsections</STRONG></A>

<UL>
<LI><A NAME="tex2html2458"
  HREF="#SECTION003610000000000000000">33.1 Fax Through Printing</A>
<LI><A NAME="tex2html2459"
  HREF="#SECTION003620000000000000000">33.2 Setgid Wrapper Binary</A>
</UL>
<!--End of Table of Child-Links-->
<HR>

<H1><A NAME="SECTION003600000000000000000">
33. Sending Faxes</A>
</H1>

<P>
<A NAME="chap:sendingfaxes"></A>
<P>
This chapter discusses the <TT>
<FONT COLOR="#0000ff">sendfax</FONT></TT> program, with reference to the
specific example of setting up an artificial printer that will automatically use a
modem to send its print jobs to remote fax machines.

<P>

<H1><A NAME="SECTION003610000000000000000">
33.1 Fax Through Printing</A>
</H1>

<P>
<I>Continuing from Section <A HREF="node24.html#sec:printtononprinter">21.10</A>...</I>

<P>
You should go now and read the <TT>
<FONT COLOR="#0000ff">sendfax</FONT></TT> section of the <TT>
<FONT COLOR="#0000ff">info</FONT></TT> page
for <TT>
<FONT COLOR="#0000ff">mgetty</FONT></TT>. The <TT>
<FONT COLOR="#0000ff">sendfax</FONT></TT> command is just one program that
sends faxes through the modem. Like <TT>
<FONT COLOR="#0000ff">mgetty</FONT></TT>, it reads a config file
in <TT>
<FONT COLOR="#0000ff">/etc/mgetty+sendfax/</FONT></TT>. This
config file is just <TT>
<FONT COLOR="#0000ff">sendfax.config</FONT></TT>
and can contain as little as

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>verbose&nbsp;y</code><br>
<code>debug&nbsp;5</code><br>
<code>fax-devices&nbsp;ttyS0</code><br>
<code>fax-id&nbsp;27&nbsp;21&nbsp;7654321</code><br>
<code>max-tries&nbsp;3</code><br>
<code>max-tries-continue&nbsp;y</code><br>
</FONT></TD></TR></TABLE><P>

<P>
Below, <TT>
<FONT COLOR="#0000ff">fax_filter.sh</FONT></TT>
is a script that sends the print job
through the fax machine after requesting the telephone number through
<TT>
<FONT COLOR="#0000ff">gdialog</FONT></TT>. <FONT COLOR="#ffa500">[<TT>
<FONT COLOR="#0000ff">gdialog</FONT></TT> is part of the <TT>
<FONT COLOR="#0000ff">gnome-utils</FONT></TT>
package.]</FONT> An appropriate <TT>
<FONT COLOR="#0000ff">/etc/printcap</FONT></TT> entry is:

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>fax:\</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;:sd=/var/spool/lpd/fax:\</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;:mx#0:\</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;:sh:\</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;:lp=/dev/null:\</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;:if=/var/spool/lpd/fax/fax_filter.sh:</code><br>
</FONT></TD></TR></TABLE><P>

<P>
The file <TT>
<FONT COLOR="#0000ff">fax_filter.sh</FONT></TT> itself could contain a script like
this <FONT COLOR="#ffa500">[Remember to rotate the
<TT>
<FONT COLOR="#0000ff">/var/log/fax</FONT></TT> log file, see page
<A HREF="node24.html#sec:logrotation"><IMG  ALIGN="BOTTOM" BORDER="1" ALT="[*]" SRC="crossref.png"></A>.]</FONT> for a modem on
<TT>
<FONT COLOR="#0000ff">/dev/ttyS0</FONT></TT>:

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>10</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>15</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>20</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>25</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>30</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>35</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>40</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>45</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>50</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>55</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>#!/bin/sh</code><br>
<code>&nbsp;</code><br>
<code>exec&nbsp;1&#062;&#062;/var/log/fax</code><br>
<code>exec&nbsp;2&#062;&#062;/var/log/fax</code><br>
<code>&nbsp;</code><br>
<code>echo</code><br>
<code>echo</code><br>
<code>echo&nbsp;$@</code><br>
<code>&nbsp;</code><br>
<code>echo&nbsp;"Starting&nbsp;fax&nbsp;`date`:&nbsp;I&nbsp;am&nbsp;`id`"</code><br>
<code>&nbsp;</code><br>
<code>export&nbsp;DISPLAY=localhost:0.0</code><br>
<code>export&nbsp;HOME=/home/lp</code><br>
<code>&nbsp;</code><br>
<code>function&nbsp;error()</code><br>
<code>{</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;gdialog&nbsp;--title&nbsp;"Send&nbsp;Fax"&nbsp;--msgbox&nbsp;"$1"&nbsp;10&nbsp;75&nbsp;||&nbsp;\</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;'Huh?&nbsp;no&nbsp;gdialog&nbsp;on&nbsp;this&nbsp;machine'</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;cd&nbsp;/</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;rm&nbsp;-Rf&nbsp;/tmp/$$fax&nbsp;||&nbsp;\</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;gdialog&nbsp;\</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;--title&nbsp;"Send&nbsp;Fax"&nbsp;\</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;--msgbox&nbsp;"rm&nbsp;-Rf&nbsp;/tmp/$$fax&nbsp;failed"&nbsp;\</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;10&nbsp;75</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;exit&nbsp;1</code><br>
<code>}</code><br>
<code>&nbsp;</code><br>
<code>mkdir&nbsp;/tmp/$$fax&nbsp;||&nbsp;error&nbsp;"mkdir&nbsp;/tmp/$$fax&nbsp;failed"</code><br>
<code>cd&nbsp;/tmp/$$fax&nbsp;||&nbsp;error&nbsp;"cd&nbsp;/tmp/$$fax&nbsp;failed"</code><br>
<code>&nbsp;</code><br>
<code>cat&nbsp;&#062;&nbsp;fax.ps</code><br>
<code>&nbsp;</code><br>
<code>if&nbsp;/usr/bin/gdialog&nbsp;\</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;--title&nbsp;"Send&nbsp;Fax"&nbsp;\</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;--inputbox&nbsp;"Enter&nbsp;the&nbsp;phone&nbsp;number&nbsp;to&nbsp;fax:"&nbsp;\</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;10&nbsp;75&nbsp;""&nbsp;2&#062;TEL&nbsp;&#059;&nbsp;then</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;:</code><br>
<code>else</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;"gdialog&nbsp;failed&nbsp;`&#060;&nbsp;TEL`"</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;rm&nbsp;-Rf&nbsp;/tmp/$$fax</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;exit&nbsp;0</code><br>
<code>fi</code><br>
<code>&nbsp;</code><br>
<code>TEL=`&#060;&nbsp;TEL`</code><br>
<code>test&nbsp;-z&nbsp;"$TEL"&nbsp;&#038;&#038;&nbsp;error&nbsp;'no&nbsp;telephone&nbsp;number&nbsp;given'</code><br>
<code>&nbsp;</code><br>
<code>cat&nbsp;fax.ps&nbsp;|&nbsp;gs&nbsp;-r204x98&nbsp;-sOutputFile=-&nbsp;-sDEVICE=faxg3&nbsp;-dBATCH&nbsp;-q&nbsp;-&nbsp;\</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;1&#062;fax.ps.g3&nbsp;||&nbsp;error&nbsp;'gs&nbsp;failed'</code><br>
<code>&nbsp;</code><br>
<code>ls&nbsp;-al&nbsp;/var/lock/</code><br>
<code>/usr/sbin/sendfax&nbsp;-x&nbsp;5&nbsp;-n&nbsp;-l&nbsp;ttyS0&nbsp;$TEL&nbsp;fax.ps.g3&nbsp;||&nbsp;\</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;error&nbsp;"sendfax&nbsp;failed"</code><br>
<code>&nbsp;</code><br>
<code>rm&nbsp;-Rf&nbsp;/tmp/$$fax</code><br>
<code>&nbsp;</code><br>
<code>exit&nbsp;0</code><br>
</FONT></TD></TR></TABLE><P>

<P>

<H1><A NAME="SECTION003620000000000000000">
33.2 Setgid Wrapper Binary</A>
</H1>

<P>
<A NAME="sec:faxsetuidbin"></A>
<P>
The above script is not enough however. Above, <TT>
<FONT COLOR="#0000ff">sendfax</FONT></TT> requires access to the
<TT>
<FONT COLOR="#0000ff">/dev/ttyS0</FONT></TT> device as well as the
<TT>
<FONT COLOR="#0000ff">/var/lock/</FONT></TT> directory (to
create a modem lock file--see Section <A HREF="node37.html#sec:ttylockfile">34.4</A>). It cannot do
that as the <TT>
<FONT COLOR="#0000ff">lp</FONT></TT> user (under which the above filter runs).
On RedHat, the command <TT>
<FONT COLOR="#0000ff">ls -ald /var/lock /dev/ttyS0</FONT></TT> reveals that only
<TT>
<FONT COLOR="#0000ff">uucp</FONT></TT> is allowed to access modems.
We can get around this restriction
by creating a setgid
(see Chapter <A HREF="node17.html#chap:permmodtimes">14</A>) binary that runs as the
<TT>
<FONT COLOR="#0000ff">uucp</FONT></TT> user. Do this by compiling the <B>C</B> program,

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red size="-1">
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-2"><code>5</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-2"><code>10</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-2"><code>15</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-2"><code>20</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-2"><code>25</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-2"><code>30</code></font><code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue size="-1">
<code>#include&nbsp;&#060;stdlib.h&#062;</code><br>
<code>#include&nbsp;&#060;string.h&#062;</code><br>
<code>#include&nbsp;&#060;stdio.h&#062;</code><br>
<code>#include&nbsp;&#060;unistd.h&#062;</code><br>
<code>&nbsp;</code><br>
<code>int&nbsp;main&nbsp;(int&nbsp;argc,&nbsp;char&nbsp;**argv)</code><br>
<code>{</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;char&nbsp;**a&#059;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;int&nbsp;i&#059;</code><br>
<code>&nbsp;</code><br>
<code>/*&nbsp;set&nbsp;the&nbsp;real&nbsp;group&nbsp;ID&nbsp;to&nbsp;that&nbsp;of&nbsp;the&nbsp;effective&nbsp;group&nbsp;ID&nbsp;*/</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;if&nbsp;(setgid&nbsp;(getegid&nbsp;()))&nbsp;{</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;perror&nbsp;("sendfax_wrapper:&nbsp;setgid&nbsp;failed")&#059;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;exit&nbsp;(1)&#059;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;}</code><br>
<code>&nbsp;</code><br>
<code>/*&nbsp;copy&nbsp;all&nbsp;arguments&nbsp;*/</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;a&nbsp;=&nbsp;(char&nbsp;**)&nbsp;malloc&nbsp;((argc&nbsp;+&nbsp;1)&nbsp;*&nbsp;sizeof&nbsp;(char&nbsp;*))&#059;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;for&nbsp;(i&nbsp;=&nbsp;1&#059;&nbsp;i&nbsp;&#060;&nbsp;argc&#059;&nbsp;i++)</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;a[i]&nbsp;=&nbsp;(char&nbsp;*)&nbsp;strdup&nbsp;(argv[i])&#059;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;a[argc]&nbsp;=&nbsp;NULL&#059;</code><br>
<code>&nbsp;</code><br>
<code>/*&nbsp;execute&nbsp;sendfax&nbsp;*/</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;a[0]&nbsp;=&nbsp;"/usr/sbin/sendfax"&#059;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;execvp&nbsp;(a[0],&nbsp;a)&#059;</code><br>
<code>&nbsp;</code><br>
<code>/*&nbsp;exit&nbsp;on&nbsp;failure&nbsp;*/</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;perror&nbsp;("sendfax_wrapper:&nbsp;failed&nbsp;to&nbsp;exececute&nbsp;/usr/sbin/sendfax")&#059;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;exit&nbsp;(1)&#059;</code><br>
<code>}</code><br>
</FONT></TD></TR></TABLE><P>
using the commands,

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>gcc&nbsp;sendfax_wrapper.c&nbsp;-o&nbsp;/usr/sbin/sendfax_wrapper&nbsp;-Wall</code><br>
<code>chown&nbsp;lp:uucp&nbsp;/usr/sbin/sendfax_wrapper</code><br>
<code>chmod&nbsp;g+s,o-rwx&nbsp;/usr/sbin/sendfax_wrapper</code><br>
</FONT></TD></TR></TABLE><P>
Then, replace
<TT>
<FONT COLOR="#0000ff">sendfax</FONT></TT> with <TT>
<FONT COLOR="#0000ff">sendfax_wrapper</FONT></TT> in the filter script. You can
see that <TT>
<FONT COLOR="#0000ff">sendfax_wrapper</FONT></TT> just executes <TT>
<FONT COLOR="#0000ff">sendfax</FONT></TT> after changing
the group ID to the <I>effective group ID</I> (GID) as obtained from the <TT>
<FONT COLOR="#0000ff">getegid</FONT></TT>
function on line 12. The effective group ID is <TT>
<FONT COLOR="#0000ff">uucp</FONT></TT> because of the
setgid group bit (i.e., <TT>
<FONT COLOR="#0000ff">g+s</FONT></TT>) in the
<TT>
<FONT COLOR="#0000ff">chmod</FONT></TT> command, and hence
<TT>
<FONT COLOR="#0000ff">sendfax</FONT></TT> runs under the <TT>
<FONT COLOR="#0000ff">uucp</FONT></TT> group with full access to the modem
device.

<P>
On your own system it may be cleaner to try implement this without a
wrapper. Debian, for example, has a <TT>
<FONT COLOR="#0000ff">dialout</FONT></TT> group for the
purposes of accessing modems. Also be aware that some distributions may
not use the <TT>
<FONT COLOR="#0000ff">uucp</FONT></TT> user in the way RedHat does and you may have to
create an alternative user especially for this task.

<P>

<P>
<HR>
<!--Navigation Panel-->
<A NAME="tex2html2456"
  HREF="node37.html">
<IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="next.png"></A> 
<A NAME="tex2html2452"
  HREF="rute.html">
<IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="up.png"></A> 
<A NAME="tex2html2446"
  HREF="node35.html">
<IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="prev.png"></A> 
<A NAME="tex2html2454"
  HREF="node1.html">
<IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents" SRC="contents.png"></A>  
<BR>
<B> Next:</B> <A NAME="tex2html2457"
  HREF="node37.html">34. uucp and uux</A>
<B> Up:</B> <A NAME="tex2html2453"
  HREF="rute.html">rute</A>
<B> Previous:</B> <A NAME="tex2html2447"
  HREF="node35.html">32. init, ? getty,</A>
 &nbsp <B>  <A NAME="tex2html2455"
  HREF="node1.html">Contents</A></B> 
<!--End of Navigation Panel-->

</BODY>
</HTML>