advanced_shell_scripting

¹⁾

$RANDOM % $#

²⁾

count + 1

³⁾

./ex13.sh; echo $? >&4) | grep 'foo' 1>&3) 4>&1` </code> This script uses nested subshells captured in backtics. Again we first duplicate stdout to another file descriptor (3). The inner subshell runs the first command, then writes the exit status to fd 4. The outer subshell redirects 4 to stdout so that it is captured by the backtics. Standard output from the first command (inner subshell) is passed into the pipeline as normal, but the final output of the pipeline is redirected to 3 so that it appears on the original stdout and is not captured by the backtics. If any of the commands really care about inheriting open file descriptors that they don't need then a more correct command line closes the descriptors before running the commands. <BLOCKQUOTE>

<font color=DARKRED>

<font color=GRAY>   1:</font> <font color=DARKGREEN><i>#!/bin/sh</i></font>
<font color=GRAY>   2:</font> <font color=DARKGREEN><i># Example 15</i></font>
<font color=GRAY>   3:</font>
<font color=GRAY>   4:</font> <font color=DARKGREEN><i># Uses ex13.sh to generate some output and give us an </i></font>

<font color=GRAY>   5:</font> <font color=DARKGREEN><i># exit status to capture.</i></font>
<font color=GRAY>   6:</font>
<font color=GRAY>   7:</font> <font color=DARKGREEN><i># Get the exit status of ex13 into $ex13stat.  </i></font>
<font color=GRAY>   8:</font> <font color=DARKGREEN><i># stdout of ex13 is processed normally</i></font>

<font color=GRAY>   9:</font>
<font color=GRAY>  10:</font> <font color=DARKGREEN><i># Save a copy of stdout</i></font>
<font color=GRAY>  11:</font> <font color=DARKBLUE>exec </font>3&gt;&amp;1
<font color=GRAY>  12:</font> <font color=DARKGREEN><i># Run a subshell, with 4 duplicated to 1 so we get it in stdout.  </i></font>

<font color=GRAY>  13:</font> <font color=DARKGREEN><i># Capture the output in ``</i></font>
<font color=GRAY>  14:</font> <font color=DARKGREEN><i># ex13stat=`( ...  ) 4&gt;&amp;1`</i></font>
<font color=GRAY>  15:</font> <font color=DARKGREEN><i># Inside the subshell, run another subshell to execute ex13, </i></font>
<font color=GRAY>  16:</font> <font color=DARKGREEN><i># and echo the status code to 4</i></font>

<font color=GRAY>  17:</font> <font color=DARKGREEN><i># (./ex13.sh; <font color=DARKBLUE>echo </font>$? &gt;&amp;4)</i></font>
<font color=GRAY>  18:</font> <font color=DARKGREEN><i># stdout from the inner subshell is processed normally, but the </i></font>
<font color=GRAY>  19:</font> <font color=DARKGREEN><i># subsequent output must be directed to 3 so it goes to the </i></font>

<font color=GRAY>  20:</font> <font color=DARKGREEN><i># original stdout and not be captured by the ``</i></font>
<font color=GRAY>  21:</font> <font color=BLACK>ex13stat=</font>`<font color=PURPLE>((./ex13.sh; <font color=DARKBLUE>echo </font>$? &gt;&amp;4) | grep 'foo' 1&gt;&amp;3) 4&gt;&amp;1</font>`

<font color=GRAY>  22:</font>
<font color=GRAY>  23:</font> <font color=DARKBLUE>echo </font>Last command status=$?
<font color=GRAY>  24:</font> <font color=DARKBLUE>echo </font>ex13stat=<font color=BLACK>$ex13stat</font>
<font color=GRAY>  25:</font>

<font color=GRAY>  26:</font> <font color=DARKGREEN><i># If any of the commands really care about inheriting open file </i></font>
<font color=GRAY>  27:</font> <font color=DARKGREEN><i># descriptors that they don't need then a more correct command line </i></font>
<font color=GRAY>  28:</font> <font color=DARKGREEN><i># closes the descriptors before running the commands</i></font>
<font color=GRAY>  29:</font> <font color=DARKBLUE>exec </font>3&gt;&amp;1

<font color=GRAY>  30:</font> <font color=BLACK>ex13stat=</font>`((./ex13.sh 3&gt;&amp;- 4&gt;&amp;- ; <font color=DARKBLUE>echo </font>$? &gt;&amp;4) | \\
<font color=GRAY>  31:</font>    grep 'foo'  1&gt;&amp;3 3&gt;&amp;- 4&gt;&amp;- ) 4&gt;&amp;1`

<font color=GRAY>  32:</font> <font color=DARKBLUE>echo </font>Last command status=$?
<font color=GRAY>  33:</font> <font color=DARKBLUE>echo </font>ex13stat=<font color=BLACK>$ex13stat</font>
</font>

</BLOCKQUOTE> Combine the above two techniques: Example: ex16 <A HREF=ex16.html TARGET=example>display</A>, <A HREF=ex16.txt TARGET=example>text</A>

exec 3&gt;&amp;1

ex13stat=`((./ex13.sh 2&gt;&amp;1 1&gt;&amp;3 3&gt;&amp;- 4&gt;&amp;- ; echo $? &gt;&amp;4) | \\

  sed s/err/ERR/ 1&gt;&amp;2 3&gt;&amp;- 4&gt;&amp;- ) 4&gt;&amp;1`

<font color=DARKRED>
<font color=GRAY>   1:</font> <font color=DARKGREEN><i>#!/bin/sh</i></font>
<font color=GRAY>   2:</font> <font color=DARKGREEN><i># Example 16</i></font>

<font color=GRAY>   3:</font>
<font color=GRAY>   4:</font> <font color=DARKGREEN><i># Uses ex13.sh to generate some output and give us an </i></font>
<font color=GRAY>   5:</font> <font color=DARKGREEN><i># exit status to capture.</i></font>
<font color=GRAY>   6:</font>
<font color=GRAY>   7:</font> <font color=DARKGREEN><i># Get the exit status of ex13 into ex13stat. </i></font>

<font color=GRAY>   8:</font> <font color=DARKGREEN><i># stderr of ex13 is processed by the pipe, stdout</i></font>
<font color=GRAY>   9:</font> <font color=DARKGREEN><i># is left alone.</i></font>
<font color=GRAY>  10:</font>
<font color=GRAY>  11:</font> <font color=DARKGREEN><i># Save a copy of stdout</i></font>

<font color=GRAY>  12:</font> <font color=DARKBLUE>exec </font>3&gt;&amp;1
<font color=GRAY>  13:</font>
<font color=GRAY>  14:</font> <font color=DARKGREEN><i># Run a subshell, with 4 copied to 1 so we get it in stdout.  </i></font>
<font color=GRAY>  15:</font> <font color=DARKGREEN><i># Capture the output in backtics`</i></font>

<font color=GRAY>  16:</font> <font color=DARKGREEN><i># ex13stat=`(    ) 4&gt;&amp;1`</i></font>
<font color=GRAY>  17:</font>
<font color=GRAY>  18:</font> <font color=DARKGREEN><i># In the subshell, run another subshell to execute ex13, and </i></font>
<font color=GRAY>  19:</font> <font color=DARKGREEN><i># echo the status code to 4</i></font>

<font color=GRAY>  20:</font> <font color=DARKGREEN><i># (./ex13.sh; <font color=DARKBLUE>echo </font>$? &gt;&amp;4)</i></font>
<font color=GRAY>  21:</font>
<font color=GRAY>  22:</font> <font color=DARKGREEN><i># stdout from the inner subshell is directed to the original stdout (3)</i></font>
<font color=GRAY>  23:</font> <font color=DARKGREEN><i># stderr is passed into the pipe for further processing.</i></font>

<font color=GRAY>  24:</font> <font color=DARKGREEN><i># stdout from the pipe is redirected back to stderr</i></font>
<font color=GRAY>  25:</font>
<font color=GRAY>  26:</font> <font color=DARKGREEN><i># Close the extra descriptors before running the commands</i></font>
<font color=GRAY>  27:</font> <font color=DARKBLUE>exec </font>3&gt;&amp;1

<font color=GRAY>  28:</font> <font color=BLACK>ex13stat=</font>`((./ex13.sh 2&gt;&amp;1 1&gt;&amp;3 3&gt;&amp;- 4&gt;&amp;- ; <font color=DARKBLUE>echo </font>$? &gt;&amp;4) | \\
<font color=GRAY>  29:</font>   sed s/err/ERR/ 1&gt;&amp;2 3&gt;&amp;- 4&gt;&amp;- ) 4&gt;&amp;1`

<font color=GRAY>  30:</font>
<font color=GRAY>  31:</font> <font color=DARKBLUE>echo </font>Last command status=$?
<font color=GRAY>  32:</font> <font color=DARKBLUE>echo </font>ex13stat=<font color=BLACK>$ex13stat</font>
<font color=GRAY>  33:</font>

</font>

</BLOCKQUOTE> A practical application of this would be running a utility such as <a href=“http://www.FreeBSD.org/cgi/man.cgi?query=dd&apropos=0&sektion=1&manpath=Red+Hat+Linux%2Fi386+9&format=html” target=manpage>

dd

</a> where the exit status is important to capture, but the error output is overly chatty and may need to be filtered before delivering to other parts of a script. </UL> (26) ======Coprocesses and Background jobs</H1> Scripts can start any number of background jobs (any external command), which run in parallel with the parent script, and asynchronously. Processes which require no further interaction or synchronization (fire and forget) are easy. Interaction with background jobs is tricky. You can use signals, pipes, named pipes, or disk files for communication. <DL> <DT>

<I>command</I> &amp;

<DD>Start command as a background process. Control returns immediately to the shell. <DT>

bgpid=$!

<DD>The special variable

$!

contains the process ID of the last background job that was started. You can save that and examine the process later (

ps -p $bgpid

) or send it a signal (

kill -HUP $bgpid

). </DL> ====ksh coprocesses==== Coprocesses are a way of starting a separate process which runs asychronously, but has stdin/stdout connected to the parent script via pipes. <DL> <DT>

<I>command</I> |&amp;

<DD>Start a coprocess with a 2-way pipe to it <DT><a href=“http://www.FreeBSD.org/cgi/man.cgi?query=read&apropos=0&sektion=1&manpath=Red+Hat+Linux%2Fi386+9&format=html” target=manpage>

read

</a>

-p <I>var</I>

<DD>Read from the pipe to the coprocess, instead of standard input <DT><a href=“http://www.FreeBSD.org/cgi/man.cgi?query=print&apropos=0&sektion=1&manpath=Red+Hat+Linux%2Fi386+9&format=html” target=manpage>

print

</a>

-p <I>args</I>

<DD>Write to the pipe connected to the coprocess, instead of standard output </DL> Multiple coprocesses can be handled by moving the special file descriptors connected to the pipes onto standard input and output, and or to explicitly specified file descriptors. <DL> <DT><a href=“http://www.FreeBSD.org/cgi/man.cgi?query=exec&apropos=0&sektion=1&manpath=Red+Hat+Linux%2Fi386+9&format=html” target=manpage>

exec

</a>

&lt;&amp;p

<DD>The input from the coprocess is moved to standard input <DT><a href=“http://www.FreeBSD.org/cgi/man.cgi?query=exec&apropos=0&sektion=1&manpath=Red+Hat+Linux%2Fi386+9&format=html” target=manpage>

exec

</a>

&gt;&amp;p

<DD>The output from the coprocess is moved to standard output </DL> Example: ex9 <A HREF=ex9.html TARGET=example>display</A>, <A HREF=ex9.txt TARGET=example>text</A> A script wants to save a copy of all output in a file, but also wants a copy to the screen. This is equivalent to always running the script as

<I>script</I> | tee <I>outfile</I>

<font color=DARKRED>
<font color=GRAY>   1:</font> <font color=DARKGREEN><i>#!/bin/ksh</i></font>
<font color=GRAY>   2:</font>
<font color=GRAY>   3:</font> <font color=DARKGREEN><i># If we have not redirected standard output, save a copy of</i></font>
<font color=GRAY>   4:</font> <font color=DARKGREEN><i># the output of this script into a file, but still send a</i></font>

<font color=GRAY>   5:</font> <font color=DARKGREEN><i># copy to the screen.</i></font>
<font color=GRAY>   6:</font>
<font color=GRAY>   7:</font> <font color=DARKBLUE>if </font>[[ -t 1 ]] ; <font color=DARKBLUE>then</font>
<font color=GRAY>   8:</font>   <font color=DARKGREEN><i># Only do this if fd 1 (stdout) is still connected</i></font>

<font color=GRAY>   9:</font>   <font color=DARKGREEN><i># to a terminal</i></font>
<font color=GRAY>  10:</font>
<font color=GRAY>  11:</font>   <font color=DARKGREEN><i># We want the standard output of the "tee" process</i></font>
<font color=GRAY>  12:</font>   <font color=DARKGREEN><i># to go explicitly to the screen (/dev/tty)</i></font>

<font color=GRAY>  13:</font>   <font color=DARKGREEN><i># and the second copy goes into a logfile named $0.out</i></font>
<font color=GRAY>  14:</font>
<font color=GRAY>  15:</font>   tee <font color=BLACK>$0</font>.out &gt;/dev/tty |&amp;
<font color=GRAY>  16:</font>

<font color=GRAY>  17:</font>   <font color=DARKGREEN><i># Our stdout all goes into this coprocess</i></font>
<font color=GRAY>  18:</font>   <font color=DARKBLUE>exec </font>1&gt;&amp;p
<font color=GRAY>  19:</font> <font color=DARKBLUE>fi</font>
<font color=GRAY>  20:</font>

<font color=GRAY>  21:</font> <font color=DARKGREEN><i># Now generate some output</i></font>
<font color=GRAY>  22:</font> <font color=DARKBLUE>print </font>"User activity snapshot on $(<font color=PURPLE>hostname) at $(date</font>)"
<font color=GRAY>  23:</font> <font color=DARKBLUE>print</font>

<font color=GRAY>  24:</font> who
</font>

</BLOCKQUOTE> Example: ex10 <A HREF=ex10.html TARGET=example>display</A>, <A HREF=ex10.txt TARGET=example>text</A> Start a coprocess to look up usernames in some database. It is faster to run a single process than to run a separate lookup for each user. <BLOCKQUOTE>

<font color=DARKRED>
<font color=GRAY>   1:</font> <font color=DARKGREEN><i>#!/bin/ksh</i></font>
<font color=GRAY>   2:</font> <font color=DARKGREEN><i># This example uses a locally written tool for Dartmouth Name Directory lookups</i></font>
<font color=GRAY>   3:</font>
<font color=GRAY>   4:</font> <font color=DARKGREEN><i># Start the dndlookup program as a coprocess</i></font>

<font color=GRAY>   5:</font> <font color=DARKGREEN><i># Tell it to output only the canonical full name, and to not print multiple matches</i></font>
<font color=GRAY>   6:</font> dndlookup -fname -u |&amp;
<font color=GRAY>   7:</font>
<font color=GRAY>   8:</font> <font color=DARKGREEN><i># move the input/output streams so we </i></font>

<font color=GRAY>   9:</font> <font color=DARKGREEN><i># can use other coprocesses too</i></font>
<font color=GRAY>  10:</font> <font color=DARKBLUE>exec </font>4&gt;&amp;p
<font color=GRAY>  11:</font> <font color=DARKBLUE>exec </font>5&lt;&amp;p

<font color=GRAY>  12:</font>
<font color=GRAY>  13:</font> <font color=DARKBLUE>echo </font>"Name file contents:"
<font color=GRAY>  14:</font> cat namefile
<font color=GRAY>  15:</font> <font color=DARKBLUE>echo</font>

<font color=GRAY>  16:</font>
<font color=GRAY>  17:</font> <font color=DARKGREEN><i># read the names from a file "namefile"</i></font>
<font color=GRAY>  18:</font> <font color=DARKBLUE>while </font>read uname; <font color=DARKBLUE>do</font>
<font color=GRAY>  19:</font>   <font color=DARKBLUE>print </font>-u4 <font color=BLACK>$uname</font>

<font color=GRAY>  20:</font>   <font color=DARKBLUE>read </font> -u5 dndname
<font color=GRAY>  21:</font>   <font color=DARKBLUE>case </font><font color=BLACK>$dndname</font> in
<font color=GRAY>  22:</font>   *many\\ matches*)

<font color=GRAY>  23:</font>     <font color=DARKGREEN><i># handle case where the name wasn't unique</i></font>
<font color=GRAY>  24:</font>     <font color=DARKBLUE>print </font>"Multiple matches to \\"<font color=BLACK>$uname</font>\\" in DND"
<font color=GRAY>  25:</font>     ;;
<font color=GRAY>  26:</font>   *no\\ match*)

<font color=GRAY>  27:</font>     <font color=DARKGREEN><i># handle case where the name wasn't found</i></font>
<font color=GRAY>  28:</font>     <font color=DARKBLUE>print </font>"No matches to \\"<font color=BLACK>$uname</font>\\" in DND"
<font color=GRAY>  29:</font>     ;;
<font color=GRAY>  30:</font>   *)

<font color=GRAY>  31:</font>     <font color=DARKGREEN><i># we seem to have a hit - process the</i></font>
<font color=GRAY>  32:</font>     <font color=DARKGREEN><i># canonical named retrieved from dndlookup</i></font>
<font color=GRAY>  33:</font>     <font color=DARKBLUE>print </font>"Unique DND match: full name for \\"<font color=BLACK>$uname</font>\\" is \\"<font color=BLACK>$dndname</font>\\""

<font color=GRAY>  34:</font>     ;;
<font color=GRAY>  35:</font>   <font color=DARKBLUE>esac</font>
<font color=GRAY>  36:</font>   sleep 2
<font color=GRAY>  37:</font> <font color=DARKBLUE>done </font>&lt; namefile

<font color=GRAY>  38:</font>
<font color=GRAY>  39:</font> <font color=DARKGREEN><i># We've read all the names, but the coprocess</i></font>
<font color=GRAY>  40:</font> <font color=DARKGREEN><i># is still running.  Close the pipe to tell it</i></font>
<font color=GRAY>  41:</font> <font color=DARKGREEN><i># we have finished.</i></font>

<font color=GRAY>  42:</font> <font color=DARKBLUE>exec </font>4&gt;&amp;-
</font>

</BLOCKQUOTE> (27) ======Variable arrays</H1> Both ksh and bash implement arrays of variables, but in somewhat different ways. ksh distinguishes between numerically indexed (small) arrays, and string indexed (associative) arrays. bash uses integers for all array indexing, but the integers need not be consecutive and unassigned array elements do not exist. Arrays must be declared before use, e,g.

typeset -A myarray

(ksh associative array), or

typeset -a myarray

(bash). Array elements are set with the syntax:

myarray[[index]]=value

and referenced with the syntax

${myarray[[index]]}

This example shows use of an array indexed by IP addresses, as strings in ksh or as non-consecutive numbers in bash. It also demonstrates use of getopt for options processing Example: getauthlogs <A HREF=getauthlogs.html TARGET=example>display</A>, <A HREF=getauthlogs.txt TARGET=example>text</A> <BLOCKQUOTE>

<font color=DARKRED>
<font color=GRAY>   1:</font> <font color=DARKGREEN><i>#!/bin/bash</i></font>

<font color=GRAY>   2:</font> <font color=DARKGREEN><i># $Header: $</i></font>
<font color=GRAY>   3:</font> <font color=DARKGREEN><i># First attempt at a consolidated auth log collection from kaserver</i></font>
<font color=GRAY>   4:</font> <font color=DARKGREEN><i># Timestamps in the raw files are NOT designed for easy sorting.</i></font>
<font color=GRAY>   5:</font> <font color=DARKGREEN><i>#</i></font>

<font color=GRAY>   6:</font> <font color=DARKGREEN><i># Options:</i></font>
<font color=GRAY>   7:</font> <font color=DARKGREEN><i>#  -i  -- translate hex IP addresses to dotted-decimal (relatively quick)</i></font>
<font color=GRAY>   8:</font> <font color=DARKGREEN><i>#  -h  -- translate hex IP addresses to DNS names (somewhat slower - DNS lookups)</i></font>
<font color=GRAY>   9:</font> <font color=DARKGREEN><i>#  -u user -- filter for the named user before translating addresses</i></font>

<font color=GRAY>  10:</font>
<font color=GRAY>  11:</font> hextodec()
<font color=GRAY>  12:</font> {
<font color=GRAY>  13:</font>    <font color=DARKGREEN><i># convert the IP address in reverse-hex to dotted-decimal</i></font>
<font color=GRAY>  14:</font>    <font color=DARKBLUE>echo </font><font color=DARKBLUE>$((0x<font color=BLACK>${1:6:2})).$((0x${1:4:2})).$((0x${1:2:2})).$((0x${1:0:2}</font>))</font>

<font color=GRAY>  15:</font> }
<font color=GRAY>  16:</font>
<font color=GRAY>  17:</font> hostlookup()
<font color=GRAY>  18:</font> {
<font color=GRAY>  19:</font>    <font color=DARKGREEN><i># Convert a decimal IP to hostname - calls 'host' each time</i></font>

<font color=GRAY>  20:</font>    <font color=BLACK>hostname=</font>$(<font color=PURPLE>host <font color=BLACK>$1</font></font>)
<font color=GRAY>  21:</font>    <font color=DARKBLUE>case </font><font color=BLACK>$hostname</font> in
<font color=GRAY>  22:</font>    *\\ not\\ found*)

<font color=GRAY>  23:</font>       <font color=DARKGREEN><i># Just echo the address we tried to look up</i></font>
<font color=GRAY>  24:</font>       <font color=DARKBLUE>echo </font>"<font color=BLACK>$1</font>"
<font color=GRAY>  25:</font>       ;;
<font color=GRAY>  26:</font>    *)

<font color=GRAY>  27:</font>       <font color=DARKGREEN><i># The result is word 5.  Lower-case it for consistency</i></font>
<font color=GRAY>  28:</font>       set <font color=BLACK>$hostname</font>
<font color=GRAY>  29:</font>       <font color=DARKBLUE>echo </font>"<font color=BLACK>$5</font>" | tr 'A-Z' 'a-z'

<font color=GRAY>  30:</font>       ;;
<font color=GRAY>  31:</font>    <font color=DARKBLUE>esac</font>
<font color=GRAY>  32:</font> }
<font color=GRAY>  33:</font>
<font color=GRAY>  34:</font> <font color=DARKGREEN><i># Options</i></font>

<font color=GRAY>  35:</font> <font color=BLACK>iptranslate=</font>0
<font color=GRAY>  36:</font> <font color=BLACK>gethostnames=</font>0
<font color=GRAY>  37:</font> <font color=BLACK>filter=</font>cat
<font color=GRAY>  38:</font> <font color=DARKBLUE>while </font>getopts ihu: o ; <font color=DARKBLUE>do</font>

<font color=GRAY>  39:</font>    <font color=DARKBLUE>case </font><font color=BLACK>$o</font> in
<font color=GRAY>  40:</font>    i) iptranslate=1 ;;
<font color=GRAY>  41:</font>    h) gethostnames=1; iptranslate=1 ;;
<font color=GRAY>  42:</font>    u) filter="grep <font color=BLACK>$OPTARG</font>" ;;

<font color=GRAY>  43:</font>    <font color=DARKBLUE>esac</font>
<font color=GRAY>  44:</font> <font color=DARKBLUE>done</font>
<font color=GRAY>  45:</font> <font color=DARKBLUE>shift </font><font color=DARKBLUE>$((<font color=BLACK>$OPTIND</font>-1))</font>

<font color=GRAY>  46:</font>
<font color=GRAY>  47:</font> <font color=DARKGREEN><i># We could get the DB server names from 'fs checkservers', but it isn't obvious what is from our cell.  We</i></font>
<font color=GRAY>  48:</font> <font color=DARKGREEN><i># could also grep CellServDB.  I cop out and hard code one known DB server and get the others from it.</i></font>
<font color=GRAY>  49:</font> <font color=BLACK>masterserver=</font>halley.dartmouth.edu

<font color=GRAY>  50:</font> <font color=BLACK>serverlist=</font>$(<font color=PURPLE>bos listhosts -server <font color=BLACK>$masterserver</font>| grep 'Host .* is ' | awk '{print <font color=BLACK>$4</font>}'</font>)
<font color=GRAY>  51:</font>
<font color=GRAY>  52:</font> <font color=DARKGREEN><i># If we want to filter usernames, it is more efficient to do it inline, before sorting, translation and hostname lookups</i></font>

<font color=GRAY>  53:</font>
<font color=GRAY>  54:</font> <font color=DARKGREEN><i># Array to hold IP address/name conversions (associative array, ksh only)</i></font>
<font color=GRAY>  55:</font> <font color=DARKGREEN><i># ksh - use -A for associative array.  bash - use -a and numeric array</i></font>
<font color=GRAY>  56:</font> <font color=DARKBLUE>typeset </font>-a hostnames

<font color=GRAY>  57:</font>
<font color=GRAY>  58:</font> (
<font color=GRAY>  59:</font> <font color=DARKBLUE>for </font>dbserver in <font color=BLACK>$serverlist</font>; <font color=DARKBLUE>do</font>
<font color=GRAY>  60:</font>    bos getlog -server <font color=BLACK>$dbserver</font> -file /usr/afs/logs/AuthLog

<font color=GRAY>  61:</font> <font color=DARKBLUE>done</font>
<font color=GRAY>  62:</font> ) | grep -v 'Fetching log file' | <font color=BLACK>$filter</font> | sed -e 's/^... //' -e 's/  \\([[1-9]]\\) / 0\\1 /' | sort --month-sort | \\
<font color=GRAY>  63:</font>     sed '-e s/ \\([[0-9a-f]][[0-9a-f]][[0-9a-f]][[0-9a-f]][[0-9a-f]][[0-9a-f]][[0-9a-f]]\\)$/ 0\\1/' |
<font color=GRAY>  64:</font>     <font color=DARKBLUE>while </font>read line; <font color=DARKBLUE>do</font>

<font color=GRAY>  65:</font>    <font color=DARKBLUE>if </font>[[ <font color=BLACK>$iptranslate</font> == 1 ]] ; <font color=DARKBLUE>then</font>
<font color=GRAY>  66:</font>       <font color=DARKGREEN><i># Ugly!</i></font>
<font color=GRAY>  67:</font>       <font color=DARKGREEN><i># Sometimes we get a 7-digit hex code in the log - the kaserver apparently drops leading zeros.</i></font>

<font color=GRAY>  68:</font>       <font color=DARKGREEN><i># The second 'sed' in the pipe catches these are fixes them.</i></font>
<font color=GRAY>  69:</font>       <font color=DARKBLUE>case </font><font color=BLACK>$line</font> in
<font color=GRAY>  70:</font>       *\\ from\\ [[0-9a-f]][[0-9a-f]][[0-9a-f]][[0-9a-f]][[0-9a-f]][[0-9a-f]][[0-9a-f]][[0-9a-f]])
<font color=GRAY>  71:</font>          <font color=DARKGREEN><i># translate the reverse-hex address</i></font>

<font color=GRAY>  72:</font>          <font color=BLACK>iphex=</font><font color=BLACK>${line##* from }</font>
<font color=GRAY>  73:</font>          <font color=DARKGREEN><i># bash version - index by numeric value only, but can be sparse array -- use the raw IP </i></font>
<font color=GRAY>  74:</font>          <font color=BLACK>ipdec=</font><font color=DARKBLUE>$((0x<font color=BLACK>$iphex</font>))</font>

<font color=GRAY>  75:</font>          <font color=BLACK>frontpart=</font><font color=BLACK>${line% from *}</font>
<font color=GRAY>  76:</font>          <font color=DARKBLUE>if </font>[[ <font color=BLACK>$gethostnames</font> == 1 ]]; <font color=DARKBLUE>then</font>
<font color=GRAY>  77:</font>             <font color=DARKGREEN><i># ksh - index on hex value as a string (iphex)</i></font>

<font color=GRAY>  78:</font>             <font color=DARKGREEN><i># bash - index on numeric value (ipdec)</i></font>
<font color=GRAY>  79:</font>             <font color=BLACK>index=</font><font color=BLACK>$ipdec</font>
<font color=GRAY>  80:</font>             <font color=DARKBLUE>if </font>[[ -z "<font color=BLACK>${hostnames[[<font color=BLACK>$index</font>]]}</font>" ]]; <font color=DARKBLUE>then</font>

<font color=GRAY>  81:</font>                hostnames[[<font color=BLACK>$index</font>]]="$(<font color=PURPLE>hostlookup $(hextodec <font color=BLACK>$iphex</font>)</font>)"
<font color=GRAY>  82:</font>             <font color=DARKBLUE>fi</font>
<font color=GRAY>  83:</font>             <font color=DARKBLUE>echo </font>"<font color=BLACK>$frontpart</font> from <font color=BLACK>${hostnames[[<font color=BLACK>$index</font>]]}</font>"

<font color=GRAY>  84:</font>          <font color=DARKBLUE>else</font>
<font color=GRAY>  85:</font>             <font color=DARKBLUE>echo </font>"<font color=BLACK>$frontpart</font> from $(<font color=PURPLE>hextodec <font color=BLACK>$iphex</font></font>)"
<font color=GRAY>  86:</font>          <font color=DARKBLUE>fi</font>

<font color=GRAY>  87:</font>          ;;
<font color=GRAY>  88:</font>       *)
<font color=GRAY>  89:</font>          <font color=DARKBLUE>echo </font>"<font color=BLACK>$line</font>"
<font color=GRAY>  90:</font>          ;;

<font color=GRAY>  91:</font>       <font color=DARKBLUE>esac</font>
<font color=GRAY>  92:</font>    <font color=DARKBLUE>else</font>
<font color=GRAY>  93:</font>       <font color=DARKGREEN><i># No ip translation, just echo the whole line</i></font>
<font color=GRAY>  94:</font>       <font color=DARKBLUE>echo </font>"<font color=BLACK>$line</font>"

<font color=GRAY>  95:</font>    <font color=DARKBLUE>fi </font>
<font color=GRAY>  96:</font> <font color=DARKBLUE>done</font>
<font color=GRAY>  97:</font>
</font>

</BLOCKQUOTE> (28) ======Delivering and Trapping Signals</H1> Unix signals (software interrupts) can be sent as asynchronous events to shell scripts, just as they can to any other program. The default behaviour is to ignore some signals and immediately exit on others. Scripts may detect signals and divert control to a handler function or external program. This is often used to perform clean-up actions before exiting, or restart certain procedures. Execution resumes where it left off, if the signal handler returns. Signal traps must be set separately inside of shell functions. Signals can be sent to a process with <a href=“http://www.FreeBSD.org/cgi/man.cgi?query=kill&apropos=0&sektion=1&manpath=Red+Hat+Linux%2Fi386+9&format=html” target=manpage>

kill

</a>. <DL> <DT><a href=“http://www.FreeBSD.org/cgi/man.cgi?query=trap&apropos=0&sektion=1&manpath=Red+Hat+Linux%2Fi386+9&format=html” target=manpage>

trap

</a>

<I>handler</I> <I>sig</I> ...

<DD>handler is a command to be read (evaluated first) and executed on receipt of the specified sigs. Signals can be specified by name or number (see kill(1

Table of Contents

When not to use shell scripts

Listing, copying and moving files and directories

Displaying text, files or parts of files

Compression and archiving

Sorting and searching for patterns

System information (users, processes, time)

Conditional tests

Merging files

Books

Online Resources

Unix-like shells and utilities for Microsoft Windows