mirror of https://github.com/tLDP/LDP
updated
This commit is contained in:
gferg
parent
1c1d88e52c
commit
32b5c22ea3
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@ -6,6 +6,77 @@
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http://personal.riverusers.com/~thegrendel/Change.log
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------------------------------------------------------------------------
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Version 3.9
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Spiceberry release, 05/15/06
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1) In the "Starting Off With a Sha-Bang" chapter:
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Added footnote that when launching a script from Bash,
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the #! isn't strictly necessary.
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(Thank you, Diane Holt, for bringing this to my attention.)
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2) In "I/O Redirection" chapter:
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At introduction to chapter,
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Added explanatory examples in introductory in-line code block.
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At "Using Exec" section,
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Added brief explanation of different effects of "exec N > filename" and "N > filename."
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(Thank you, Ahmed Darwish, for both of the above.)
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3) In "Special Characters" chapter:
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At "$" entry, added an additional usage example.
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At "$$" entry, added footnote explaining of what a PID is.
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At redirection operators entry, added "<>" description.
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At "-" entry, fixup on "bunzip2" example.
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(Thanks, Roman.)
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4) In "Miscellaneous Commands" section of "External Commands" chapter:
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At "yes" entry,
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added parsing of variables.
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5) In "File and Archiving Commands" section of "External Commands" Chapter:
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At "gzip" entry, added note about "-c" option.
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6) In "Manipulating Strings" section of "Variables Revisited" chapter:
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At "${string%%substring}" entry,
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added "ra2ogg.sh" example script.
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7) In "Bash, version 3" section of "Bash, versions 2 and 3" chapter
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Added "Bash, version 3.1" subsection.
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Entry for "+=" operator.
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8) In "Subshells" chapter:
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Modified final note about command list within curly brackets,
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per suggestion of Andreas Kühne.
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9) In "Gotchas" chapter:
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Converted separate entries to bulleted-item list.
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Added entry for error in leaving out termination semicolon in command
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block within curly braces.
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(Thank you, Andreas Kühne.)
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10) In "Writing Scripts" section of "Exercises" appendix:
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Added "Checking whether a process is still running" exercise
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("Easy" section).
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11) "System and Administrative Commands" chapter:
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Minor revision of "strace" entry.
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Added "ltrace" entry.
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Added "lspci" entry.
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12) In "Contributed Scripts" appendix:
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Minor modification to "life.sh" script, to check for missing startfile.
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13) In "Reference Cards" appendix:
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Fixed up error in "Miscellaneous Constructs" table (terminating
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semicolon in command list within curly brackets).
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(Thank you, Andreas Kühne.)
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14) In "Revision History" appendix:
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Fixed embarrassing typos.
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15) Various minor fixups on example scripts.
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Version 3.8
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Blaeberry release, 02/26/06
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@ -43,7 +43,7 @@ prepend.sh (lines 18 and 28)
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array-assign.bash
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cdll (lines 51-53, 59, 63-69, 82-83, 85, 463, 521, 567-568, 570,
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580-586, 637, 656-658)
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directory-info.sh (lines 273 and 353)
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directory-info.sh (lines 36, 166, 273 and 353)
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is-spammer.sh (comments on lines 4, 35, and 51)
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bashrc (comments on lines 596 and 618)
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commentblock.sh (lines 4 and 23)
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@ -52,7 +52,6 @@ self-document2.sh (line 8)
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dev-tcp.sh (line 14)
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archiveweblogs.sh (comment in line 4)
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multiple-processes.sh (line 143)
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directory-info.sh (lines 36 and 166)
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catscripts.sh (lines 12 and 21)
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is_spammer.bash (comments on various lines)
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iscan.sh (comment in line 10)
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@ -62,3 +61,4 @@ hash-example.sh (comment in line 3: < --> <, > --> >)
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quote-fetch.sh (comment in line 26: & --> &)
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ftpget.sh (comment in line 28)
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whx.sh (comment in line 259)
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In-line code block at beginning of "I/O Redirection" chapter, line 41.
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@ -321,6 +321,7 @@ Uncomment line below to generate index.
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<!ENTITY testcgi SYSTEM "test-cgi.sh">
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<!ENTITY spawnscr SYSTEM "spawn.sh">
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<!ENTITY iscan SYSTEM "iscan.sh">
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<!ENTITY ra2ogg SYSTEM "ra2ogg.sh">
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<!ENTITY namesdata SYSTEM "names.data">
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<!ENTITY hashlib SYSTEM "Hash.lib">
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<!ENTITY hashexample SYSTEM "hash-example.sh">
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@ -350,19 +351,12 @@ Uncomment line below to generate index.
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</affiliation>
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</author>
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<releaseinfo>3.8</releaseinfo>
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<pubdate>26 February 2006</pubdate>
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<releaseinfo>3.9</releaseinfo>
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<pubdate>15 May 2006</pubdate>
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<revhistory>
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<revision>
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<revnumber>3.6</revnumber>
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<date>28 Aug 2005</date>
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<authorinitials>mc</authorinitials>
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<revremark>'POKEBERRY' release: Bugfix Update.</revremark>
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</revision>
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<revision>
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<revnumber>3.7</revnumber>
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<date>23 Oct 2005</date>
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@ -377,6 +371,13 @@ Uncomment line below to generate index.
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<revremark>'BLAEBERRY' release: Minor Update.</revremark>
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</revision>
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<revision>
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<revnumber>3.9</revnumber>
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<date>15 May 2006</date>
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<authorinitials>mc</authorinitials>
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<revremark>'SPICEBERRY' release: Minor Update.</revremark>
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</revision>
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</revhistory>
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@ -397,7 +398,7 @@ Uncomment line below to generate index.
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introduction to programming concepts.</para>
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<para><ulink
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url="http://personal.riverusers.com/~thegrendel/abs-guide-3.8.tar.bz2">
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url="http://personal.riverusers.com/~thegrendel/abs-guide-3.9.tar.bz2">
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The latest update of this document</ulink>, as an archived, <link
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linkend="bzipref">bzip2-ed</link> <quote>tarball</quote>
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including both the SGML source and rendered HTML, may
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@ -761,6 +762,11 @@ exit $WHATEVER # Doesn't matter. The script will not exit here.</programlisting
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shell directives. The second example, above, requires the
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initial <token>#!</token>, since the variable assignment line,
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<userinput>lines=50</userinput>, uses a shell-specific construct.
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<footnote><para>If Bash is your default shell, then the
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<token>#!</token> isn't necessary at the beginning of a script.
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However, if launching a script from a different shell, such as
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<firstterm>tcsh</firstterm>, then you <emphasis>will</emphasis>
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need the <token>#!</token>.</para></footnote>
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Note again that <userinput>#!/bin/sh</userinput> invokes the default
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shell interpreter, which defaults to <filename>/bin/bash</filename>
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on a Linux machine.</para>
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@ -1672,7 +1678,7 @@ echo $var2 # 23skidoo</programlisting>
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</varlistentry>
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<varlistentry>
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<term><token>$$</token></term>
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<term><anchor id="processidref"><token>$$</token></term>
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<indexterm>
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<primary>$$</primary>
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</indexterm>
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@ -1690,8 +1696,15 @@ echo $var2 # 23skidoo</programlisting>
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<listitem><formalpara><title>process ID variable</title>
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<para>The <link linkend="proccid">$$ variable</link>
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holds the <emphasis>process ID</emphasis> of the script in
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which it appears.</para>
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holds the <emphasis>process ID</emphasis>
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<footnote>
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<para>A <firstterm>PID</firstterm>, or
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<firstterm>process ID</firstterm>, is a number assigned
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to a running process. The <emphasis>PID</emphasis>s
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of running processes may be viewed with a <link
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linkend="ppssref">ps</link> command.</para>
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</footnote>
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of the script in which it appears.</para>
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</formalpara>
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</listitem>
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@ -1790,11 +1803,12 @@ cp file22.{txt,backup}
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<listitem>
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<para><anchor id="codeblockref"></para>
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<formalpara><title>Block of code [curly brackets]</title>
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<para>Also referred to as an <quote>inline group</quote>,
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this construct, in effect, creates an anonymous
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function. However, unlike a <link
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<para>Also referred to as an <firstterm>inline group</firstterm>,
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this construct, in effect, creates an <firstterm>anonymous
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function</firstterm> (a function without a
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name). However, unlike in a <quote>standard</quote> <link
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linkend="functionref">function</link>, the variables
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in a code block remain visible to the remainder of the
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inside a code block remain visible to the remainder of the
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script.</para></formalpara>
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<para> <screen><prompt>bash$ </prompt><userinput>{ local a;
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@ -1974,7 +1988,7 @@ echo ${Array[1]}</programlisting></para>
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<varlistentry>
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<term><token>></token> <token>&></token> <token>>&</token> <token>>></token> <token><</token></term>
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<term><token>></token> <token>&></token> <token>>&</token> <token>>></token> <token><</token> <token><></token></term>
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<indexterm>
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<primary>></primary>
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</indexterm>
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@ -2026,10 +2040,17 @@ echo ${Array[1]}</programlisting></para>
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to <filename>stderr</filename>.</para>
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<para><userinput>scriptname >>filename</userinput> appends
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the output of <filename>scriptname</filename>
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to file <filename>filename</filename>. If
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<filename>filename</filename> does not already exist,
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it will be created.</para>
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the output of <filename>scriptname</filename>
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to file <filename>filename</filename>. If
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<filename>filename</filename> does not already exist,
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it is created.</para>
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<para><userinput>[i]<>filename</userinput>
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opens file <filename>filename</filename> for reading
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and writing, and assigns <link linkend="fdref">file
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descriptor</link> <token>i</token> to it. If
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<filename>filename</filename> does not exist, it is
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created.</para>
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<formalpara><title><link linkend="processsubref">process substitution</link></title>
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@ -2429,11 +2450,11 @@ fi</programlisting>
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# If there are hidden files in /source/directory.
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</programlisting></para>
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<para><programlisting>bunzip2 linux-2.6.13.tar.bz2 | tar xvf -
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# --uncompress tar file-- | --then pass it to "tar"--
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# If "tar" has not been patched to handle "bunzip2",
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# this needs to be done in two discrete steps, using a pipe.
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# The purpose of the exercise is to unarchive "bzipped" kernel source.
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<para><programlisting>bunzip2 -c linux-2.6.16.tar.bz2 | tar xvf -
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# --uncompress tar file-- | --then pass it to "tar"--
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# If "tar" has not been patched to handle "bunzip2",
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#+ this needs to be done in two discrete steps, using a pipe.
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# The purpose of the exercise is to unarchive "bzipped" kernel source.
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</programlisting></para>
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<para>Note that in this context the <quote>-</quote> is not
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@ -6456,8 +6477,10 @@ echo "Last command argument processed = $last_cmd_arg"
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<para>The <varname>$PPID</varname> of a process is
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the process ID (<varname>pid</varname>) of its parent process.
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<footnote><para>The PID of the currently running script is
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<varname>$$</varname>, of course.</para></footnote>
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<footnote>
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<para>The PID of the currently running script is
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<varname>$$</varname>, of course.</para>
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</footnote>
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</para>
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<para>Compare this with the <link
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@ -7551,11 +7574,19 @@ echo ${stringZ%%b*c} # a
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# Strip out longest match between 'b' and 'c', from back of $stringZ.</programlisting>
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</para>
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<para>This operator is useful for generating filenames.</para>
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<example id="cvt">
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<title>Converting graphic file formats, with filename change</title>
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<programlisting>&cvt;</programlisting>
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</example>
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<example id="ra2ogg">
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<title>Converting streaming audio files to
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<emphasis>ogg</emphasis></title>
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<programlisting>&ra2ogg;</programlisting>
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</example>
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<para>A simple emulation of <link linkend="getopty">getopt</link>
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using substring extraction constructs.</para>
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@ -8629,6 +8660,7 @@ echo $? # 1
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<para>The argument <replaceable>list</replaceable> may contain wild cards.</para>
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<para><anchor id="needsemicolon"></para>
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<para>If <firstterm>do</firstterm> is on same line as
|
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<firstterm>for</firstterm>, there needs to be a semicolon
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after list.</para>
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@ -8816,7 +8848,7 @@ echo $? # 1
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</cmdsynopsis></para>
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<para>As is the case with <firstterm>for loops</firstterm>,
|
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<para><link linkend="needsemicolon">As is the case with <firstterm>for loops</firstterm></link>,
|
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placing the <firstterm>do</firstterm> on the same line as
|
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the condition test requires a semicolon.</para>
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@ -12222,7 +12254,7 @@ OneYearAgo=$(date --date='1 year ago')</programlisting></para>
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</varlistentry>
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<varlistentry>
|
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<term><command>sleep</command></term>
|
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<term><anchor id="sleepref"><command>sleep</command></term>
|
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<indexterm>
|
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<primary>sleep</primary>
|
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</indexterm>
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@ -13886,6 +13918,11 @@ function write_utf8_string {
|
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command is <command>gunzip</command>, which is the equivalent of
|
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<command>gzip -d</command>.</para>
|
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|
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<note><para>The <option>-c</option> option sends the output of
|
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<command>gzip</command> to <filename>stdout</filename>. This
|
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is useful when <link linkend="piperef">piping</link> to other
|
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commands.</para></note>
|
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|
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<para>The <command>zcat</command> filter decompresses a
|
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<emphasis>gzipped</emphasis> file to
|
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<filename>stdout</filename>, as possible input to a pipe or
|
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|
|
@ -13895,6 +13932,7 @@ function write_utf8_string {
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utility). The <command>zcat</command> command is equivalent to
|
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<command>gzip -dc</command>.</para>
|
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|
||||
|
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<caution><para>On some commercial UNIX systems, <command>zcat</command>
|
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is a synonym for <command>uncompress -c</command>,
|
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and will not work on <emphasis>gzipped</emphasis>
|
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|
|
@ -16325,6 +16363,22 @@ done</programlisting></para>
|
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linkend="fdiskref">fdisk</link>. It may have unintended
|
||||
side-effects.</para></warning>
|
||||
|
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<note>
|
||||
<para>The <command>yes</command> command parses variables.
|
||||
For example:</para>
|
||||
<para>
|
||||
<screen><prompt>bash$ </prompt><userinput>yes $BASH_VERSION</userinput>
|
||||
<computeroutput>3.00.16(1)-release
|
||||
3.00.16(1)-release
|
||||
3.00.16(1)-release
|
||||
3.00.16(1)-release
|
||||
3.00.16(1)-release
|
||||
. . .</computeroutput>
|
||||
</screen>
|
||||
</para>
|
||||
<para>This <quote>feature</quote> may not be particularly useful.</para>
|
||||
</note>
|
||||
|
||||
</listitem>
|
||||
</varlistentry>
|
||||
|
||||
|
|
@ -17758,18 +17812,23 @@ setserial /dev/$DEVICE irq 0 ; setserial /dev/$DEVICE irq $IRQ</programlisting><
|
|||
</indexterm>
|
||||
<indexterm>
|
||||
<primary>command</primary>
|
||||
<secondary>strace</secondary>
|
||||
<secondary>trace</secondary>
|
||||
</indexterm>
|
||||
<listitem>
|
||||
<para>Diagnostic and debugging tool for tracing system
|
||||
calls and signals. The simplest way of invoking it is
|
||||
<command>strace COMMAND</command>.</para>
|
||||
<para><command>S</command>ystem <command>trace</command>:
|
||||
diagnostic and debugging tool for tracing <firstterm>system
|
||||
calls</firstterm> and signals. This command and
|
||||
<command>ltrace</command>, following, are useful for
|
||||
diagnosing why a given program or package fails to
|
||||
run . . . perhaps due to missing libraries or related
|
||||
causes.</para>
|
||||
|
||||
<para>
|
||||
<screen><prompt>bash$ </prompt><userinput>strace df</userinput>
|
||||
<computeroutput>execve("/bin/df", ["df"], [/* 45 vars */]) = 0
|
||||
uname({sys="Linux", node="bozo.localdomain", ...}) = 0
|
||||
brk(0) = 0x804f5e4
|
||||
|
||||
...</computeroutput>
|
||||
</screen>
|
||||
</para>
|
||||
|
|
@ -17780,6 +17839,37 @@ setserial /dev/$DEVICE irq 0 ; setserial /dev/$DEVICE irq $IRQ</programlisting><
|
|||
</listitem>
|
||||
</varlistentry>
|
||||
|
||||
<varlistentry>
|
||||
<term><command>ltrace</command></term>
|
||||
<indexterm>
|
||||
<primary>ltrace</primary>
|
||||
</indexterm>
|
||||
<indexterm>
|
||||
<primary>command</primary>
|
||||
<secondary>trace</secondary>
|
||||
</indexterm>
|
||||
<listitem>
|
||||
<para><command>L</command>ibrary <command>trace</command>:
|
||||
diagnostic and debugging tool that traces <firstterm>library calls</firstterm>
|
||||
invoked by a given command.</para>
|
||||
|
||||
<para>
|
||||
<screen><prompt>bash$ </prompt><userinput>ltrace df</userinput>
|
||||
<computeroutput>__libc_start_main(0x804a910, 1, 0xbfb589a4, 0x804fb70, 0x804fb68 <unfinished ...>:
|
||||
setlocale(6, "") = "en_US.UTF-8"
|
||||
bindtextdomain("coreutils", "/usr/share/locale") = "/usr/share/locale"
|
||||
textdomain("coreutils") = "coreutils"
|
||||
__cxa_atexit(0x804b650, 0, 0, 0x8052bf0, 0xbfb58908) = 0
|
||||
getenv("DF_BLOCK_SIZE") = NULL
|
||||
|
||||
...</computeroutput>
|
||||
</screen>
|
||||
</para>
|
||||
|
||||
</listitem>
|
||||
</varlistentry>
|
||||
|
||||
|
||||
<varlistentry>
|
||||
<term><anchor id="nmapref"><command>nmap</command></term>
|
||||
<indexterm>
|
||||
|
|
@ -18370,7 +18460,7 @@ Average: all 6.33 1.70 14.71 0.00 77.26</compute
|
|||
<title><anchor id="jobcontrolsys1">Job Control</title>
|
||||
|
||||
<varlistentry>
|
||||
<term><command>ps</command></term>
|
||||
<term><anchor id="ppssref"><command>ps</command></term>
|
||||
<indexterm>
|
||||
<primary>ps</primary>
|
||||
</indexterm>
|
||||
|
|
@ -19364,6 +19454,7 @@ mount -o loop /dev/loop0 /mnt # Mount it.
|
|||
bMaxPacketSize0 8
|
||||
idVendor 0x0000
|
||||
idProduct 0x0000
|
||||
|
||||
. . .</computeroutput>
|
||||
</screen>
|
||||
</para>
|
||||
|
|
@ -19371,6 +19462,36 @@ mount -o loop /dev/loop0 /mnt # Mount it.
|
|||
</listitem>
|
||||
</varlistentry>
|
||||
|
||||
<varlistentry>
|
||||
<term><command>lspci</command></term>
|
||||
<indexterm>
|
||||
<primary>lspci</primary>
|
||||
</indexterm>
|
||||
<indexterm>
|
||||
<primary>command</primary>
|
||||
<secondary>pci</secondary>
|
||||
</indexterm>
|
||||
<listitem>
|
||||
<para>Lists <firstterm>pci</firstterm> busses present.</para>
|
||||
|
||||
<para>
|
||||
<screen><prompt>bash$ </prompt><userinput>lspci</userinput>
|
||||
<computeroutput>00:00.0 Host bridge: Intel Corporation 82845 845 (Brookdale) Chipset Host Bridge (rev 04)
|
||||
00:01.0 PCI bridge: Intel Corporation 82845 845 (Brookdale) Chipset AGP Bridge (rev 04)
|
||||
00:1d.0 USB Controller: Intel Corporation 82801CA/CAM USB (Hub #1) (rev 02)
|
||||
00:1d.1 USB Controller: Intel Corporation 82801CA/CAM USB (Hub #2) (rev 02)
|
||||
00:1d.2 USB Controller: Intel Corporation 82801CA/CAM USB (Hub #3) (rev 02)
|
||||
00:1e.0 PCI bridge: Intel Corporation 82801 Mobile PCI Bridge (rev 42)
|
||||
|
||||
. . .</computeroutput>
|
||||
</screen>
|
||||
</para>
|
||||
|
||||
</listitem>
|
||||
</varlistentry>
|
||||
|
||||
|
||||
|
||||
<varlistentry>
|
||||
<term><command>mkbootdisk</command></term>
|
||||
<indexterm>
|
||||
|
|
@ -20588,17 +20709,26 @@ let "z += 3" # Quotes permit the use of spaces in variable assignment.
|
|||
# --------------------------------------------------------------------
|
||||
|
||||
1>filename
|
||||
# Redirect stdout to file "filename".
|
||||
# Redirect stdout to file "filename."
|
||||
1>>filename
|
||||
# Redirect and append stdout to file "filename".
|
||||
# Redirect and append stdout to file "filename."
|
||||
2>filename
|
||||
# Redirect stderr to file "filename".
|
||||
# Redirect stderr to file "filename."
|
||||
2>>filename
|
||||
# Redirect and append stderr to file "filename".
|
||||
# Redirect and append stderr to file "filename."
|
||||
&>filename
|
||||
# Redirect both stdout and stderr to file "filename".
|
||||
# Redirect both stdout and stderr to file "filename."
|
||||
|
||||
M>N
|
||||
# "M" is a file descriptor, which defaults to 1, if not explicitly set.
|
||||
# "N" is a filename.
|
||||
# File descriptor "M" is redirect to file "N."
|
||||
M>&N
|
||||
# "M" is a file descriptor, which defaults to 1, if not set.
|
||||
# "N" is another file descriptor.
|
||||
|
||||
#==============================================================================
|
||||
|
||||
# Redirecting stdout, one line at a time.
|
||||
LOGFILE=script.log
|
||||
|
||||
|
|
@ -20773,6 +20903,22 @@ exec 3>&- # Now close it for the remainder of the s
|
|||
file. This sends all command output that would normally go
|
||||
to <filename>stdout</filename> to that file.</para>
|
||||
|
||||
<important>
|
||||
<para>
|
||||
<command>exec N > filename</command> affects the entire
|
||||
script or <emphasis>current shell</emphasis>. Redirection in
|
||||
the <link linkend="processidref">PID</link> of the script or shell
|
||||
from that point on has changed. However . . .
|
||||
</para>
|
||||
<para>
|
||||
<command>N > filename</command> affects only the newly-forked process,
|
||||
not the entire script or shell.
|
||||
</para>
|
||||
<para>Thank you, Ahmed Darwish, for pointing this out.</para>
|
||||
</important>
|
||||
|
||||
|
||||
|
||||
<example id="reassignstdout">
|
||||
<title>Redirecting <filename>stdout</filename> using
|
||||
<command>exec</command></title>
|
||||
|
|
@ -21191,9 +21337,9 @@ echo "This line had better not echo." # Follows an 'exit' command.</programlist
|
|||
|
||||
<para><anchor id="herestringsref"></para>
|
||||
|
||||
<para>A <emphasis>here string</emphasis> can be considered as
|
||||
a stripped-down form of <emphasis>here document</emphasis>. It
|
||||
consists of nothing more than <command>COMMAND
|
||||
<para>A <firstterm>here string</firstterm> can be considered as
|
||||
a stripped-down form of a <firstterm>here document</firstterm>.
|
||||
It consists of nothing more than <command>COMMAND
|
||||
<<<$WORD</command>, where <varname>$WORD</varname>
|
||||
is expanded and fed to the <filename>stdin</filename> of
|
||||
<varname>COMMAND</varname>.</para>
|
||||
|
|
@ -21455,6 +21601,8 @@ exit 0</programlisting></para></footnote>
|
|||
<para><anchor id="dollarsignref"></para>
|
||||
<para>The dollar sign -- <token>$</token> -- at the end of an
|
||||
RE matches the end of a line.</para>
|
||||
<para><quote>XXX$</quote> matches <emphasis>XXX</emphasis> at the
|
||||
end of a line.</para>
|
||||
<para><quote>^$</quote> matches blank lines.</para>
|
||||
</listitem>
|
||||
|
||||
|
|
@ -22246,7 +22394,7 @@ fi
|
|||
<note><para>A command block between <replaceable>curly
|
||||
braces</replaceable> does <emphasis>not</emphasis> launch
|
||||
a subshell.</para>
|
||||
<para>{ command1; command2; command3; ... }</para></note>
|
||||
<para>{ command1; command2; command3; . . . commandN; }</para></note>
|
||||
|
||||
|
||||
</chapter> <!-- Subshells -->
|
||||
|
|
@ -24574,7 +24722,14 @@ trap 'echo "Control-C disabled."' 2
|
|||
|
||||
<para><anchor id="bash3gotcha"></para>
|
||||
|
||||
<para>Assigning reserved words or characters to variable names.
|
||||
|
||||
|
||||
<itemizedlist>
|
||||
|
||||
<listitem>
|
||||
<para>Assigning reserved words or characters to variable names.</para>
|
||||
|
||||
<para>
|
||||
<programlisting>case=value0 # Causes problems.
|
||||
23skidoo=value1 # Also problems.
|
||||
# Variable names starting with a digit are reserved by the shell.
|
||||
|
|
@ -24587,9 +24742,12 @@ echo $_ # $_ is a special variable set to last arg of last command.
|
|||
xyz((!*=value2 # Causes severe problems.
|
||||
# As of version 3 of Bash, periods are not allowed within variable names.</programlisting>
|
||||
</para>
|
||||
</listitem>
|
||||
|
||||
<listitem>
|
||||
<para>Using a hyphen or other reserved characters in a variable name (or
|
||||
function name).
|
||||
function name).</para>
|
||||
<para>
|
||||
<programlisting>var-1=23
|
||||
# Use 'var_1' instead.
|
||||
|
||||
|
|
@ -24601,9 +24759,12 @@ function-whatever () # Error
|
|||
function.whatever () # Error
|
||||
# Use 'functionWhatever ()' instead.</programlisting>
|
||||
</para>
|
||||
</listitem>
|
||||
|
||||
<listitem>
|
||||
<para>Using the same name for a variable and a function. This can make a
|
||||
script difficult to understand.
|
||||
script difficult to understand.</para>
|
||||
<para>
|
||||
<programlisting>do_something ()
|
||||
{
|
||||
echo "This function does something with \"$1\"."
|
||||
|
|
@ -24615,13 +24776,17 @@ do_something do_something
|
|||
|
||||
# All this is legal, but highly confusing.</programlisting>
|
||||
</para>
|
||||
</listitem>
|
||||
|
||||
|
||||
|
||||
<listitem>
|
||||
<para><anchor id="wsbad">Using <link
|
||||
linkend="whitespaceref">whitespace</link> inappropriately.
|
||||
In contrast to other programming languages, Bash can be quite
|
||||
finicky about whitespace.
|
||||
finicky about whitespace.</para>
|
||||
|
||||
<para>
|
||||
<programlisting>var1 = 23 # 'var1=23' is correct.
|
||||
# On line above, Bash attempts to execute command "var1"
|
||||
# with the arguments "=" and "23".
|
||||
|
|
@ -24632,24 +24797,46 @@ if [ $a -le 5] # if [ $a -le 5 ] is correct.
|
|||
# if [ "$a" -le 5 ] is even better.
|
||||
# [[ $a -le 5 ]] also works.</programlisting>
|
||||
</para>
|
||||
</listitem>
|
||||
|
||||
|
||||
<listitem>
|
||||
<para>Not terminating with a <firstterm>semicolon</firstterm> the final
|
||||
command in a <link linkend="codeblockref">code block within curly
|
||||
brackets</link>.</para>
|
||||
<para>
|
||||
<programlisting>{ ls -l; df; echo "Done." }
|
||||
# bash: syntax error: unexpected end of file
|
||||
|
||||
{ ls -l; df; echo "Done."; }
|
||||
# ^ ### Final command needs semicolon.</programlisting>
|
||||
</para>
|
||||
</listitem>
|
||||
|
||||
|
||||
<listitem>
|
||||
<para>
|
||||
Assuming uninitialized variables (variables before a value is
|
||||
assigned to them) are <quote>zeroed out</quote>. An
|
||||
uninitialized variable has a value of <quote>null</quote>,
|
||||
<emphasis>not</emphasis> zero.
|
||||
<emphasis>not</emphasis> zero.</para>
|
||||
|
||||
<para>
|
||||
<programlisting>#!/bin/bash
|
||||
|
||||
echo "uninitialized_var = $uninitialized_var"
|
||||
# uninitialized_var =</programlisting>
|
||||
|
||||
</para>
|
||||
</listitem>
|
||||
|
||||
|
||||
<listitem>
|
||||
<para>Mixing up <emphasis>=</emphasis> and <emphasis>-eq</emphasis> in
|
||||
a test. Remember, <emphasis>=</emphasis> is for comparing literal
|
||||
variables and <emphasis>-eq</emphasis> for integers.
|
||||
variables and <emphasis>-eq</emphasis> for integers.</para>
|
||||
|
||||
<para>
|
||||
<programlisting>if [ "$a" = 273 ] # Is $a an integer or string?
|
||||
if [ "$a" -eq 273 ] # If $a is an integer.
|
||||
|
||||
|
|
@ -24677,8 +24864,10 @@ then
|
|||
fi # Aborts with an error message.
|
||||
# test.sh: [: 273.0: integer expression expected</programlisting>
|
||||
</para>
|
||||
</listitem>
|
||||
|
||||
|
||||
<listitem>
|
||||
<para>Misusing <link linkend="scomparison1">string comparison</link>
|
||||
operators.</para>
|
||||
|
||||
|
|
@ -24686,41 +24875,55 @@ fi # Aborts with an error message.
|
|||
<title>Numerical and string comparison are not equivalent</title>
|
||||
<programlisting>&badop;</programlisting>
|
||||
</example>
|
||||
</listitem>
|
||||
|
||||
|
||||
<listitem>
|
||||
<para>Sometimes variables within <quote>test</quote> brackets
|
||||
([ ]) need to be quoted (double quotes). Failure to do so may
|
||||
cause unexpected behavior. See <xref linkend="strtest">, <xref
|
||||
linkend="redir2">, and <xref linkend="arglist">.</para>
|
||||
</listitem>
|
||||
|
||||
|
||||
<listitem>
|
||||
<para>Commands issued from a script may fail to execute because
|
||||
the script owner lacks execute permission for them. If a user
|
||||
cannot invoke a command from the command line, then putting it
|
||||
into a script will likewise fail. Try changing the attributes of
|
||||
the command in question, perhaps even setting the suid bit
|
||||
(as root, of course).</para>
|
||||
</listitem>
|
||||
|
||||
|
||||
|
||||
<listitem>
|
||||
<para>Attempting to use <command>-</command> as a redirection
|
||||
operator (which it is not) will usually result in an unpleasant
|
||||
surprise.
|
||||
surprise.</para>
|
||||
<para>
|
||||
<programlisting>command1 2> - | command2 # Trying to redirect error output of command1 into a pipe...
|
||||
# ...will not work.
|
||||
|
||||
command1 2>& - | command2 # Also futile.
|
||||
|
||||
Thanks, S.C.</programlisting></para>
|
||||
</listitem>
|
||||
|
||||
|
||||
|
||||
|
||||
<listitem>
|
||||
<para>Using Bash <link linkend="bash2ref">version 2+</link>
|
||||
functionality may cause a bailout with error messages. Older
|
||||
Linux machines may have version 1.XX of Bash as the default
|
||||
installation.
|
||||
installation.</para>
|
||||
<para>
|
||||
<programlisting>#!/bin/bash
|
||||
|
||||
minimum_version=2
|
||||
# Since Chet Ramey is constantly adding features to Bash,
|
||||
# you may set $minimum_version to 2.XX, or whatever is appropriate.
|
||||
# you may set $minimum_version to 2.XX, 3.XX, or whatever is appropriate.
|
||||
E_BAD_VERSION=80
|
||||
|
||||
if [ "$BASH_VERSION" \< "$minimum_version" ]
|
||||
|
|
@ -24731,14 +24934,19 @@ then
|
|||
fi
|
||||
|
||||
...</programlisting></para>
|
||||
</listitem>
|
||||
|
||||
|
||||
|
||||
<listitem>
|
||||
<para>Using Bash-specific functionality in a Bourne shell script
|
||||
(<userinput>#!/bin/sh</userinput>) on a non-Linux machine
|
||||
may cause unexpected behavior. A Linux system usually aliases
|
||||
<command>sh</command> to <command>bash</command>, but this does
|
||||
not necessarily hold true for a generic UNIX machine.</para>
|
||||
</listitem>
|
||||
|
||||
<listitem>
|
||||
<para>Using undocumented features in Bash turns out to be a
|
||||
dangerous practice. In previous releases of this
|
||||
book there were several scripts that depended on the
|
||||
|
|
@ -24748,13 +24956,18 @@ fi
|
|||
did not apply to <emphasis>negative</emphasis> integers.
|
||||
Unfortunately, in version 2.05b and later, that loophole
|
||||
disappeared. See <xref linkend="returntest">.</para>
|
||||
</listitem>
|
||||
|
||||
|
||||
|
||||
<listitem>
|
||||
<para>
|
||||
A script with DOS-type newlines (<replaceable>\r\n</replaceable>)
|
||||
will fail to execute, since <userinput>#!/bin/bash\r\n</userinput>
|
||||
is not recognized, <emphasis>not</emphasis> the same as the
|
||||
expected <userinput>#!/bin/bash\n</userinput>. The fix is to
|
||||
convert the script to UNIX-style newlines.
|
||||
is <emphasis>not</emphasis> recognized, <emphasis>not</emphasis>
|
||||
the same as the expected <userinput>#!/bin/bash\n</userinput>. The
|
||||
fix is to convert the script to UNIX-style newlines.</para>
|
||||
<para>
|
||||
<programlisting>#!/bin/bash
|
||||
|
||||
echo "Here"
|
||||
|
|
@ -24771,24 +24984,34 @@ echo "There"
|
|||
exit 0</programlisting>
|
||||
</para>
|
||||
|
||||
</listitem>
|
||||
|
||||
|
||||
|
||||
<listitem>
|
||||
<para>A shell script headed by <userinput>#!/bin/sh</userinput>
|
||||
will not run in full Bash-compatibility mode. Some Bash-specific
|
||||
functions might be disabled. Scripts that need complete
|
||||
access to all the Bash-specific extensions should start with
|
||||
<userinput>#!/bin/bash</userinput>.</para>
|
||||
</listitem>
|
||||
|
||||
<listitem>
|
||||
<para><link linkend="indentedls">Putting whitespace in front of
|
||||
the terminating limit string</link> of a <link
|
||||
linkend="heredocref">here document</link> will cause unexpected
|
||||
behavior in a script.</para>
|
||||
</listitem>
|
||||
|
||||
|
||||
<listitem>
|
||||
<para><anchor id="parchildprobref"></para>
|
||||
|
||||
<para>A script may not <command>export</command> variables back
|
||||
to its <link linkend="forkref">parent process</link>, the shell,
|
||||
or to the environment. Just as we learned in biology, a child
|
||||
process can inherit from a parent, but not vice versa.
|
||||
process can inherit from a parent, but not vice versa.</para>
|
||||
<para>
|
||||
<programlisting>WHATEVER=/home/bozo
|
||||
export WHATEVER
|
||||
exit 0</programlisting>
|
||||
|
|
@ -24797,9 +25020,16 @@ exit 0</programlisting>
|
|||
|
||||
</computeroutput>
|
||||
<prompt>bash$ </prompt></screen>
|
||||
Sure enough, back at the command prompt, $WHATEVER remains unset.
|
||||
</para>
|
||||
</para>
|
||||
<para>
|
||||
Sure enough, back at the command prompt, $WHATEVER remains unset.
|
||||
</para>
|
||||
|
||||
</listitem>
|
||||
|
||||
|
||||
|
||||
<listitem>
|
||||
<para>Setting and manipulating variables in a <link
|
||||
linkend="subshellsref">subshell</link>, then attempting
|
||||
to use those same variables outside the scope of the subshell will
|
||||
|
|
@ -24809,7 +25039,11 @@ exit 0</programlisting>
|
|||
<title>Subshell Pitfalls</title>
|
||||
<programlisting>&subpit;</programlisting>
|
||||
</example>
|
||||
</listitem>
|
||||
|
||||
|
||||
|
||||
<listitem>
|
||||
<para><anchor id="badread0"></para>
|
||||
<para><link linkend="piperef">Piping</link>
|
||||
<command>echo</command> output to a <link
|
||||
|
|
@ -24899,32 +25133,44 @@ find $HOME -type f -atime +30 -size 100k | {
|
|||
<programlisting>tail -f /var/log/messages | grep "$ERROR_MSG" >> error.log
|
||||
# The "error.log" file will not have anything written to it.</programlisting>
|
||||
</para>
|
||||
</listitem>
|
||||
|
||||
|
||||
<para>--</para>
|
||||
|
||||
|
||||
<listitem>
|
||||
<para>Using <quote>suid</quote> commands within scripts is risky,
|
||||
as it may compromise system security.
|
||||
<footnote><para>Setting the <emphasis>suid</emphasis> permission on
|
||||
the script itself has no effect.</para></footnote>
|
||||
</para>
|
||||
</listitem>
|
||||
|
||||
|
||||
<listitem>
|
||||
<para>Using shell scripts for CGI programming may be problematic. Shell
|
||||
script variables are not <quote>typesafe</quote>, and this can cause
|
||||
undesirable behavior as far as CGI is concerned. Moreover, it is
|
||||
difficult to <quote>cracker-proof</quote> shell scripts.</para>
|
||||
</listitem>
|
||||
|
||||
|
||||
<listitem>
|
||||
<para>Bash does not handle the <link linkend="doubleslashref">double slash
|
||||
(<token>//</token>) string</link> correctly.</para>
|
||||
</listitem>
|
||||
|
||||
|
||||
<listitem>
|
||||
<para>Bash scripts written for Linux or BSD systems may need
|
||||
fixups to run on a commercial UNIX (or Apple OSX) machine. Such
|
||||
scripts often employ GNU commands and filters which have greater
|
||||
functionality than their generic UNIX counterparts. This is
|
||||
particularly true of such text processing utilites as <link
|
||||
linkend="trref">tr</link>.</para>
|
||||
</listitem>
|
||||
|
||||
|
||||
</itemizedlist>
|
||||
|
||||
<epigraph>
|
||||
<attribution>A.J. Lamb and H.W. Petrie</attribution>
|
||||
|
|
@ -26563,6 +26809,51 @@ fi</programlisting></para>
|
|||
</caution>
|
||||
|
||||
|
||||
<sect2> <!-- Bash, Version 3.1 -->
|
||||
<title>Bash, version 3.1</title>
|
||||
|
||||
<para>The version 3.1 update of Bash introduces a number of bugfixes
|
||||
and a few minor changes.</para>
|
||||
|
||||
<itemizedlist>
|
||||
|
||||
<listitem>
|
||||
<para>The <token>+=</token> operator is now permitted in
|
||||
in places where previously only the <token>=</token>
|
||||
assignment operator was recognized.</para>
|
||||
|
||||
<para><programlisting>a=1
|
||||
echo $a # 1
|
||||
|
||||
a+=5 # Won't work under versions of Bash earlier than 3.1.
|
||||
echo $a # 15
|
||||
|
||||
a+=Hello
|
||||
echo $a # 15Hello</programlisting>
|
||||
</para>
|
||||
|
||||
<para>Here, <token>+=</token> functions as a <firstterm>string
|
||||
concatenation</firstterm> operator. Note that its behavior
|
||||
in this particular context is different than within a
|
||||
<link linkend="letref">let</link> construct.</para>
|
||||
|
||||
<para><programlisting>a=1
|
||||
echo $a # 1
|
||||
|
||||
let a+=5 # Integer arithmetic, rather than string concatenation.
|
||||
echo $a # 6
|
||||
|
||||
let a+=Hello # Doesn't "add" anything to a.
|
||||
echo $a # 6</programlisting>
|
||||
</para>
|
||||
|
||||
</listitem>
|
||||
|
||||
</itemizedlist>
|
||||
|
||||
|
||||
</sect2> <!-- Bash, Version 3 -->
|
||||
|
||||
</sect1> <!-- Bash, Version 3 -->
|
||||
|
||||
</chapter> <!-- Bash, versions 2 and 3 -->
|
||||
|
|
@ -26861,7 +27152,8 @@ fi</programlisting></para>
|
|||
Chris Morgan, Walter Dnes, Linc Fessenden, Michael Iatrou, Pharis
|
||||
Monalo, Jesse Gough, Fabian Kreutz, Mark Norman, Harald Koenig,
|
||||
Peter Knowles, Francisco Lobo, Mariusz Gniazdowski, Tedman Eng,
|
||||
and David Lawyer (himself an author of four HOWTOs).</para>
|
||||
Achmed Darwish, Andreas Kühne, and David Lawyer (himself
|
||||
an author of four HOWTOs).</para>
|
||||
|
||||
<para>My gratitude to <ulink url="mailto:chet@po.cwru.edu">Chet
|
||||
Ramey</ulink> and Brian Fox for writing <firstterm>Bash</firstterm>,
|
||||
|
|
@ -28523,7 +28815,7 @@ fi</programlisting></para>
|
|||
<entry><link linkend="ivrref">Indirect variable reference</link></entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>{ command1; command2 }</option></entry>
|
||||
<entry><option>{ command1; command2; . . . commandN; }</option></entry>
|
||||
<entry>Block of code</entry>
|
||||
</row>
|
||||
<row>
|
||||
|
|
@ -30629,6 +30921,18 @@ done < `tail -f /var/log/messages`</programlisting>
|
|||
</listitem>
|
||||
</varlistentry>
|
||||
|
||||
<varlistentry>
|
||||
<term><command>Checking whether a process is still running</command></term>
|
||||
<listitem>
|
||||
<para>Given a <link linkend="processidref">process ID</link>
|
||||
(<firstterm>PID</firstterm>) as an argument, this script
|
||||
will check, at user-specified intervals, whether
|
||||
the given process is still running. You may use
|
||||
the <link linkend="ppssref">ps</link> and <link
|
||||
linkend="sleepref">sleep</link> commands.</para>
|
||||
</listitem>
|
||||
</varlistentry>
|
||||
|
||||
<varlistentry>
|
||||
<term><command>Primes</command></term>
|
||||
<listitem>
|
||||
|
|
@ -31351,7 +31655,7 @@ fairly detailed rundown on the Playfair Cipher and its solution methods.</progra
|
|||
<title>Revision History</title>
|
||||
|
||||
<synopsis>
|
||||
This document first appeared as a HOWTO in the late spring
|
||||
This document first appeared as a 60-page HOWTO in the late spring
|
||||
of 2000. Since then, it has gone through quite a number of
|
||||
updates and revisions. This book could not have been written
|
||||
without the assistance of the Linux community, and especially
|
||||
|
|
@ -31527,22 +31831,27 @@ fairly detailed rundown on the Playfair Cipher and its solution methods.</progra
|
|||
<row>
|
||||
<entry><option>3.5</option></entry>
|
||||
<entry>05 Jun 2005</entry>
|
||||
<entry>BOXBERRY release: Bugfixes, some materials added.</entry>
|
||||
<entry>BOXBERRY release: Bugfixes, some material added.</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>3.6</option></entry>
|
||||
<entry>28 Aug 2005</entry>
|
||||
<entry>POKEBERRY release: Bugfixes, some materials added.</entry>
|
||||
<entry>POKEBERRY release: Bugfixes, some material added.</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>3.7</option></entry>
|
||||
<entry>23 Oct 2005</entry>
|
||||
<entry>WHORTLEBERRY release: Bugfixes, some materials added.</entry>
|
||||
<entry>WHORTLEBERRY release: Bugfixes, some material added.</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>3.8</option></entry>
|
||||
<entry>26 Feb 2006</entry>
|
||||
<entry>BLAEBERRY release: Bugfixes, some materials added.</entry>
|
||||
<entry>BLAEBERRY release: Bugfixes, some material added.</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>3.9</option></entry>
|
||||
<entry>15 May 2006</entry>
|
||||
<entry>SPICEBERRY release: Bugfixes, some material added.</entry>
|
||||
</row>
|
||||
</tbody>
|
||||
</tgroup>
|
||||
|
|
@ -31555,7 +31864,7 @@ fairly detailed rundown on the Playfair Cipher and its solution methods.</progra
|
|||
<title>Mirror Sites</title>
|
||||
|
||||
<para><ulink
|
||||
url="http://personal.riverusers.com/~thegrendel/abs-guide-3.7.tar.bz2">
|
||||
url="http://thegrendel.150m.com/abs-guide-3.9.tar.bz2">
|
||||
The latest update of this document</ulink>, as an archived
|
||||
<quote>tarball</quote>
|
||||
including both the SGML source and rendered HTML, may
|
||||
|
|
|
|||
|
|
@ -65,7 +65,7 @@ do
|
|||
then
|
||||
exchange $index `expr $index + 1` # Swap.
|
||||
fi
|
||||
let "index += 1"
|
||||
let "index += 1" # Or, index+=1 on Bash, ver. 3.1 or newer.
|
||||
done # End of inner loop
|
||||
|
||||
# ----------------------------------------------------------------------
|
||||
|
|
|
|||
|
|
@ -28,6 +28,9 @@ while [ "$index" -lt "$element_count" ]
|
|||
do # List all the elements in the array.
|
||||
echo ${colors[$index]}
|
||||
let "index = $index + 1"
|
||||
# Or:
|
||||
# index+=1
|
||||
# if running Bash, version 3.1 or later.
|
||||
done
|
||||
# Each array element listed on a separate line.
|
||||
# If this is not desired, use echo -n "${colors[$index]} "
|
||||
|
|
|
|||
|
|
@ -13,7 +13,7 @@
|
|||
#+ The gcd = dividend, on the final pass.
|
||||
#
|
||||
# For an excellent discussion of Euclid's algorithm, see
|
||||
# Jim Loy's site, http://www.jimloy.com/number/euclids.htm.
|
||||
#+ Jim Loy's site, http://www.jimloy.com/number/euclids.htm.
|
||||
|
||||
|
||||
# ------------------------------------------------------
|
||||
|
|
@ -33,7 +33,7 @@ gcd ()
|
|||
{
|
||||
|
||||
dividend=$1 # Arbitrary assignment.
|
||||
divisor=$2 #+ It doesn't matter which of the two is larger.
|
||||
divisor=$2 #! It doesn't matter which of the two is larger.
|
||||
# Why not?
|
||||
|
||||
remainder=1 # If uninitialized variable used in loop,
|
||||
|
|
|
|||
|
|
@ -31,12 +31,23 @@ startfile=gen0 # Read the starting generation from the file "gen0".
|
|||
#
|
||||
if [ -n "$1" ] # Specify another "generation 0" file.
|
||||
then
|
||||
if [ -e "$1" ] # Check for existence.
|
||||
then
|
||||
startfile="$1"
|
||||
fi
|
||||
fi
|
||||
|
||||
############################################
|
||||
# Abort script if "startfile" not specified
|
||||
#+ AND
|
||||
#+ "gen0" not present.
|
||||
|
||||
E_NOSTARTFILE=68
|
||||
|
||||
if [ ! -e "$startfile" ]
|
||||
then
|
||||
echo "Startfile \""$startfile"\" missing!"
|
||||
exit $E_NOSTARTFILE
|
||||
fi
|
||||
############################################
|
||||
|
||||
|
||||
ALIVE1=.
|
||||
DEAD1=_
|
||||
|
|
@ -337,9 +348,9 @@ done
|
|||
|
||||
echo
|
||||
|
||||
exit 0
|
||||
exit 0 # END
|
||||
|
||||
|
||||
# --------------------------------------------------------------
|
||||
|
||||
# The grid in this script has a "boundary problem."
|
||||
# The the top, bottom, and sides border on a void of dead cells.
|
||||
|
|
|
|||
|
|
@ -9,7 +9,7 @@
|
|||
# The first 20 terms of the series are:
|
||||
# 1 1 2 3 3 4 5 5 6 6 6 8 8 8 10 9 10 11 11 12
|
||||
|
||||
# See Hofstadter's book, "Goedel, Escher, Bach: An Eternal Golden Braid",
|
||||
# See Hofstadter's book, _Goedel, Escher, Bach: An Eternal Golden Braid_,
|
||||
#+ p. 137, ff.
|
||||
|
||||
|
||||
|
|
|
|||
|
|
@ -2181,7 +2181,7 @@ This HOWTO has been removed for review. </Para>
|
|||
Linksys-Blue-Box-Router-HOWTO</ULink>,
|
||||
<CiteTitle>Linksys Blue Box Router HOWTO</CiteTitle>
|
||||
</Para><Para>
|
||||
<CiteTitle>Updated: Dec 2005</CiteTitle>.
|
||||
<CiteTitle>Updated: May 2006</CiteTitle>.
|
||||
Hints and tips for managing Linksys
|
||||
routers from a Linux system, including the firmware upgrade procedure. </Para>
|
||||
</ListItem>
|
||||
|
|
|
|||
|
|
@ -1078,7 +1078,7 @@ scanner device on a system running Linux. </Para>
|
|||
Linksys-Blue-Box-Router-HOWTO</ULink>,
|
||||
<CiteTitle>Linksys Blue Box Router HOWTO</CiteTitle>
|
||||
</Para><Para>
|
||||
<CiteTitle>Updated: Dec 2005</CiteTitle>.
|
||||
<CiteTitle>Updated: May 2006</CiteTitle>.
|
||||
Hints and tips for managing Linksys
|
||||
routers from a Linux system, including the firmware upgrade procedure. </Para>
|
||||
</ListItem>
|
||||
|
|
|
|||
|
|
@ -937,7 +937,7 @@ How to enable the Linux IP Masquerade feature on a given Linux host. </Para>
|
|||
Linksys-Blue-Box-Router-HOWTO</ULink>,
|
||||
<CiteTitle>Linksys Blue Box Router HOWTO</CiteTitle>
|
||||
</Para><Para>
|
||||
<CiteTitle>Updated: Dec 2005</CiteTitle>.
|
||||
<CiteTitle>Updated: May 2006</CiteTitle>.
|
||||
Hints and tips for managing Linksys
|
||||
routers from a Linux system, including the firmware upgrade procedure. </Para>
|
||||
</ListItem>
|
||||
|
|
|
|||
|
|
@ -1,6 +1,6 @@
|
|||
<?xml version="1.0"?>
|
||||
<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
|
||||
"http://docbook.org/xml/4.2/docbookx.dtd" [
|
||||
<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
|
||||
"http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" [
|
||||
<!ENTITY howto "http://www.tldp.org/HOWTO/">
|
||||
<!ENTITY mini-howto "http://www.tldp.org/HOWTO/mini/">
|
||||
<!ENTITY home "http://www.catb.org/~esr/">
|
||||
|
|
@ -20,6 +20,15 @@
|
|||
</author>
|
||||
|
||||
<revhistory>
|
||||
<revision>
|
||||
<revnumber>2.3</revnumber>
|
||||
<date>2006-05-19</date>
|
||||
<authorinitials>esr</authorinitials>
|
||||
<revremark>
|
||||
Revised the list of open firmware distributions, and other minor
|
||||
corrections.
|
||||
</revremark>
|
||||
</revision>
|
||||
<revision>
|
||||
<revnumber>2.2</revnumber>
|
||||
<date>2005-12-01</date>
|
||||
|
|
@ -149,7 +158,7 @@ machine over a cable.</para>
|
|||
|
||||
<para>Also note that if you go looking for one of these now, be sure to get
|
||||
the WRT54GL — note the L suffix. At Version 5 and up, the vanilla
|
||||
WRT54G is different hardware with less RAM that runs a propriatary
|
||||
WRT54G is different hardware with less RAM that runs a proprietary
|
||||
VxWorks OS.</para>
|
||||
|
||||
</sect2>
|
||||
|
|
@ -184,9 +193,7 @@ ignore you.</para>
|
|||
to be used as gateway boxes on a home Ethernet. Typically, you'll hook one
|
||||
up to a DSL or cable modem, which will automatically switch into bridge
|
||||
mode and simply pass packets between your ISP's router and the Linksys box.
|
||||
Here's a <ulink
|
||||
url='http://www.linksys.com/products/group.asp?grid=33&scid=35'>recognition
|
||||
chart</ulink> of these products.</para>
|
||||
</para>
|
||||
|
||||
<para>If you want to use a general-purpose PC running Linux as a firewall,
|
||||
have fun — but these little boxes are more efficient. The nicest
|
||||
|
|
@ -202,9 +209,9 @@ year, and I heard grumbling from others about similar problems.
|
|||
Unfortunately when I tried other low-end brands (Belkin, Buffalo) they
|
||||
proved to have gross design errors. The Belkin had brain-damage in its
|
||||
firewall rules that interfered with local SMTP, and the Buffalo
|
||||
intermittently refused connections for no apparent reason. So I'm back
|
||||
with Linksys. hoping my WRT54G doesn't turn into a doorstop within a couple
|
||||
of months.</para>
|
||||
intermittently refused connections for no apparent reason. So I went back
|
||||
with Linksys, hoping my WRT54G wouldn't turn into a doorstop within a couple
|
||||
of months. As of mid-2006, I've been OK for about 24 months.</para>
|
||||
|
||||
<para>(Building one of these puppies is not rocket science. I can only
|
||||
conjecture that the competitive pressure is driving the manufacturers to cut
|
||||
|
|
@ -218,8 +225,8 @@ what marketers call a flank guard, a low-end brand designed to protect the
|
|||
margins and brand image of Cisco's commercial-grade networking products.
|
||||
This means that Linksys boxes are no longer acquiring new firmware
|
||||
features, and some old ones like stateful packet inspection almost
|
||||
certainly won't be coming back. Provided you can live wthin these limits,
|
||||
this is actually good; simpler firmware is stable firmware.</para>
|
||||
certainly won't be coming back. Provided you can live within these limits,
|
||||
this is actually good; simpler firmware is more stable firmware.</para>
|
||||
|
||||
<para>At minimum, a live Linksys box will do the following things for
|
||||
you:</para>
|
||||
|
|
@ -260,7 +267,7 @@ built into the firmware, a good thing if your net connection is
|
|||
down.</para>
|
||||
|
||||
<para>Unfortunately, you're in trouble if you have to bring in Linksys tech
|
||||
support. On the one occasion that I called them, the first tech
|
||||
support. On the one occasion that I called them (in 2003), the first tech
|
||||
I raised couldn't even speak English, and the second was barely competent
|
||||
at it. Both were complete and utter idiots whose response to any
|
||||
nontrivial question was to put me on infinite hold while they went
|
||||
|
|
@ -285,8 +292,7 @@ reported</ulink> that turning off the remote admin feature doesn't work
|
|||
side. This bug is still present in the 2.02 firmware, October 2004. It
|
||||
means that if you leave your password at default, any script kiddie can
|
||||
break in, steal your WEP, and scramble your configuration. The Linksys
|
||||
people get the moron medal with oak-leaf cluster for this
|
||||
screwup.</para>
|
||||
people get the moron medal with oak-leaf cluster for this screwup.</para>
|
||||
|
||||
<para>(I don't know if this bug is still present in the 3.x firmware. It
|
||||
would be a good idea to check.)</para>
|
||||
|
|
@ -321,7 +327,7 @@ network.</para></step>
|
|||
</procedure>
|
||||
|
||||
<para>There are two more steps for older firmware versions only. You can
|
||||
ignore these if you have 2.x firmware.</para>
|
||||
ignore these if you have 2.x or later firmware.</para>
|
||||
|
||||
<procedure>
|
||||
<step><para><emphasis role='bold'>Disable AOL Parental Controls.</emphasis>
|
||||
|
|
@ -365,9 +371,9 @@ WINE. Not recommended.</para>
|
|||
<para>The third way is to use <application>tftp</application>. This is how
|
||||
I did it the first time, before Linksys added the <quote>Upgrade
|
||||
firmware</quote> to the firmware, and I document it here for completeness
|
||||
even though I now recommend that method. There is a tftp client included
|
||||
with Red Hat Linux. To upgrade your firmware this way, do the following
|
||||
steps:</para>
|
||||
even though I now recommend their upgrade method. There is a tftp client
|
||||
included with Red Hat Linux. To upgrade your firmware this way, do the
|
||||
following steps:</para>
|
||||
|
||||
<procedure>
|
||||
<step>
|
||||
|
|
@ -378,9 +384,7 @@ your basic settings but clear some advanced ones.</para>
|
|||
</step>
|
||||
<step>
|
||||
<para><emphasis role='bold'>Download a copy of the new firmware.</emphasis>
|
||||
You should find it at <ulink
|
||||
url="http://www.linksys.com/download/firmware.asp?dlid=1"> Firmware
|
||||
Upgrades for your Linksys Products</ulink> on the Linksys site. Note that
|
||||
Follow the Downloads link from the Linkys main page. Note that
|
||||
what you get may well be marked <quote>For Windows Users</quote> and be a
|
||||
zip archive. Open it in a scratch directory, because it will rudely create
|
||||
several Windows files wherever you unpack it. The file you need will be
|
||||
|
|
@ -395,9 +399,9 @@ until both the Password and Confirm fields are blank, and click
|
|||
Apply.</para>
|
||||
</step>
|
||||
<step>
|
||||
<para><emphasis role='bold'>Cross your fingers and load the firmware.</emphasis>
|
||||
The command session you want will to see will look something like
|
||||
this, with your router's IP address substituted for
|
||||
<para><emphasis role='bold'>Cross your fingers and load the
|
||||
firmware.</emphasis> The command session you want will to see will look
|
||||
something like this, with your router's IP address substituted for
|
||||
192.168.1.1:</para>
|
||||
|
||||
<screen>
|
||||
|
|
@ -425,11 +429,7 @@ the firmware version number will have changed.</para>
|
|||
</sect1>
|
||||
<sect1><title>Hacking the hardware</title>
|
||||
|
||||
<para>There is a <ulink
|
||||
url="http://www.bextreme.net/wap11web/">page</ulink> that tells you how to
|
||||
casemod the Linksys WAP11 wireless access point.</para>
|
||||
|
||||
<para>Linksys boxes have firmware support for a serial console, The circuit
|
||||
<para>Linksys boxes have firmware support for a serial console. The circuit
|
||||
board has traces for two serial ports, but you have to do some fairly
|
||||
serious modding to get them working. <ulink
|
||||
url="http://www.rwhitby.net/wrt54gs/serial.html">This page</ulink> will
|
||||
|
|
@ -438,12 +438,12 @@ show you how.</para>
|
|||
</sect1>
|
||||
<sect1><title>Hacking the software</title>
|
||||
|
||||
<para>Linxsys routers run Linux from firmware. Linksys supplies <ulink
|
||||
url="http://www.linksys.com/support/gpl.asp">source code</ulink> on its
|
||||
site.</para>
|
||||
<para>Linksys routers run Linux from firmware. Linksys supplies source
|
||||
code on its site; look for "GPL Code Center" under technical
|
||||
support.</para>
|
||||
|
||||
<para>There are several replacements for the WRT54G firmware. All
|
||||
add certain commn features such as (a) the capability to ssh into the
|
||||
add certain common features such as (a) the capability to ssh into the
|
||||
Linux running on the box, (b) European WiFi channels, and (c) VPN
|
||||
service.</para>
|
||||
|
||||
|
|
@ -459,6 +459,14 @@ Supports SNMP/mrtg. Said to have a good interface, convenient for home use.
|
|||
<listitem><para>
|
||||
Intended for Wireless ISPs, lots of stuff for routing and repeater operation.
|
||||
Open source, but you can buy support and private-release subscriptions.
|
||||
This outfit has been slammed for GPL noncompliance and apparently lost
|
||||
a lot of the good reputation it used to have.
|
||||
</para></listitem>
|
||||
</varlistentry>
|
||||
<varlistentry>
|
||||
<term><ulink url='http://dd-wrt.com'>DD-WRT</ulink></term>
|
||||
<listitem><para>
|
||||
A fork of the SveaSoft codebase from a few years back.
|
||||
</para></listitem>
|
||||
</varlistentry>
|
||||
<varlistentry>
|
||||
|
|
@ -501,8 +509,8 @@ Wrt54g</ulink> by Seattle wireless.net.</para>
|
|||
</sect1>
|
||||
<sect1 id="Utilities"><title>Utilities</title>
|
||||
|
||||
<para>There is a Unix utility called <application>linksysmon</application> that
|
||||
talks with these boxes via SNMP. There is a <ulink
|
||||
<para>There is a Unix utility called <application>linksysmon</application>
|
||||
that talks with these boxes via SNMP. Look at the <ulink
|
||||
url="http://woogie.net/linksysmon/">Linksysmon project site</ulink>.</para>
|
||||
|
||||
<para>Linksysmon is a tool for monitoring Linksys BEFSR41 and BEFSR11
|
||||
|
|
|
|||
Loading…
Reference in New Issue