mirror of https://github.com/tLDP/LDP
updated
This commit is contained in:
gferg
parent
04cfa193ca
commit
2bbea82cc4
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@ -6,6 +6,120 @@
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http://personal.riverusers.com/~thegrendel/Change.log
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------------------------------------------------------------------------
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Version 3.2
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Blueberry release, 02/06/05
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1) In the "Starting Off With a Sha-Bang" chapter:
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Fixed small typo (if [ $# -ne $Number_of_expected args ]).
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Thanks, Robbie Morrison.
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Added epigraph to "Why Shell Programming?" section.
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2) In "Special Characters" chapter:
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At "&" entry, added comment about Nasimuddin Ansari's suggested change
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to "background-loop.sh" example.
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3) In "Colorizing Scripts" section of "Miscellany" chapter:
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Added link to Henry/teikedvl's utility for creating colorized scripts.
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4) In "Complex Functions and Function Complexities" chapter:
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Added "func-cmdlinearg.sh" example script to clear up confusion
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about command-line args passed to a script.
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5) In "Local Variables" section of "Functions" chapter:
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Fixed typo in example in footnote.
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(Thank you, jaka kranjc.)
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6) In "File and Archiving Commands" section of "External Commands" Chapter:
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At "files" entry, added example of finding specific file types
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in a given directory.
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7) In "Communications Commands" section of "External Commands" chapter:
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At "ssh" entry, added caution about ssh using up loop's stdin.
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(Thanks, Jason Bechtel.)
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8) In "Special Variable Types" section of "Introduction to Variables" chapter
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Some fixups for "ex18.sh" example.
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Added Chris Monson's example of finding last command line parameter.
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9) In "Parameter Substitution" section of "Variables Revisited" chapter:
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Added material to "param-sub.sh" example.
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10) In "Double Parentheses Construct" section of "Variables Revisited"
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chapter:
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In "c-vars.sh" example, added instances of differing side-effects
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of pre- and post-increment operators.
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(Thanks, Jeroen Domburg.)
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11) In "Indirect References to Variables" section of "Variables Revisited"
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chapter:
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Added Nils Radtke's example of building dynamic variable names.
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12) In "Text Processing" section of "External Commands" Chapter:
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Added extra explanatory lines at "grep" listing.
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Moved "manview.sh" script example from Contributed Script appendix
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to "groff, tbl, eqn" entry.
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13) In the "Shell Wrappers" section of "Miscellany" chapter:
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Added redirection comment to "ex3.sh" example.
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(Thanks, jaka kranjc.)
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14) In "Regular Expressions" chapter:
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Added listing of components of REs.
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Streamlined the discussion following.
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15) In "$RANDOM" section of "Variables Revisited" chapter:
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Added footnote about randomness and pseudorandomness.
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Added a couple of cross-links in the text.
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16) In "System and Administrative Commands" chapter:
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Added usage example at "last" entry.
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17) In "/dev" section of "/dev and /proc" chapter:
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Changed reference URL from slashdot.org to net.cn (a known spam ISP).
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Added to footnote about mounting a USB flash drive.
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18) In "Gotchas" chapter:
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Added note about not hyphenating function names.
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19) In "Bibliography" section:
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Added William Parks' Dec. '04 "Linux Gazette" article to his listing.
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Added entry for "Unix Oneliners."
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Added "http://www.zazzybob.com" entry.
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20) In "Writing Scripts" section of "Exercises" appendix:
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In "Intermediate" section, added "Integer or String" exercise .
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In "Intermediate" section, added "Logged in User Information"
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exercise .
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21) In "Contributed Scripts" appendix:
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Added "cdll" expanded 'cd' command.
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(Thanks, Phil Braham.)
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Added "wgetter2.bash" example script.
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(Thanks, Little Monster <monster@monstruum.co.uk>.)
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22) In "Localization" appendix:
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Again, fixed quoting problem in "localized.sh" in-line example
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(per Bruno Haible).
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23) In "Important System Directories" appendix:
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Corrected "/sys" entry.
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Added "/mnt," "/dev," "/proc," and "/media" entries.
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24) In "Analyzing Scripts" section of "Exercises" appendix:
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Added short example script.
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25) Added comment block to sample .bashrc file (Appendix G).
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(Thanks, Ane-Pieter Wieringa.)
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26) Deleted unwanted space in ": <<XXX" here document comments in various
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scripts and text body.
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27) Various miscellaneous fixups in example scripts.
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(Thanks, Kalin Kozhuharov and others.)
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Version 3.1
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Bayberry release, 11/14/04
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@ -41,8 +41,15 @@ avoid-subshell.sh (lines 24, 25, and 33)
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usb.sh (line 28)
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prepend.sh (lines 18 and 28)
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array-assign.bash
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archiveweblogs.sh (comment in line 4)
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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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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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self-document.sh (line 14)
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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 61)
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directory-info.sh (lines 36 and 166)
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is_spammer.bash (comments on various lines)
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@ -301,8 +301,10 @@ Uncomment line below to generate index.
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<!ENTITY archiveweblogs SYSTEM "archiveweblogs.sh">
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<!ENTITY devtcp SYSTEM "dev-tcp.sh">
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<!ENTITY multipleproc SYSTEM "multiple-processes.sh">
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<!ENTITY funccmdlinearg SYSTEM "func-cmdlinearg.sh">
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<!ENTITY isspammer SYSTEM "is-spammer.sh">
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<!ENTITY isspammer2 SYSTEM "is_spammer.bash">
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<!ENTITY wgetter2 SYSTEM "wgetter2.bash">
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<!ENTITY exercisingdd SYSTEM "exercising-dd.sh">
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<!ENTITY quotefetch SYSTEM "quote-fetch.sh">
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<!ENTITY avoidsubshell SYSTEM "avoid-subshell.sh">
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@ -311,6 +313,7 @@ Uncomment line below to generate index.
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<!ENTITY testcgi SYSTEM "test-cgi.sh">
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<!ENTITY namesdata SYSTEM "names.data">
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<!ENTITY gen0data SYSTEM "gen0">
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<!ENTITY cdll SYSTEM "cdll">
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<!ENTITY bashrc SYSTEM "bashrc">
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]>
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@ -329,19 +332,12 @@ Uncomment line below to generate index.
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</affiliation>
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</author>
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<releaseinfo>3.1</releaseinfo>
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<pubdate>14 November 2004</pubdate>
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<releaseinfo>3.2</releaseinfo>
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<pubdate>06 February 2005</pubdate>
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<revhistory>
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<revision>
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<revnumber>2.8</revnumber>
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<date>11 July 2004</date>
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<authorinitials>mc</authorinitials>
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<revremark>'ELDERBERRY' release: Minor update.</revremark>
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</revision>
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<revision>
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<revnumber>3.0</revnumber>
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<date>03 Oct 2004</date>
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@ -356,6 +352,13 @@ Uncomment line below to generate index.
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<revremark>'BAYBERRY' release: Bugfix update.</revremark>
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</revision>
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<revision>
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<revnumber>3.2</revnumber>
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<date>06 Feb 2005</date>
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<authorinitials>mc</authorinitials>
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<revremark>'BLUEBERRY' release: Minor update.</revremark>
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</revision>
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</revhistory>
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@ -376,7 +379,7 @@ 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-3.1.tar.bz2">
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url="http://personal.riverusers.com/~thegrendel/abs-guide-3.2.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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@ -419,6 +422,13 @@ Uncomment line below to generate index.
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<chapter id="why-shell">
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<title>Why Shell Programming?</title>
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<epigraph>
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<attribution>Herbert Mayer</attribution>
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<para>No programming language is perfect. There is not even a single
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best language; there are only languages well suited or perhaps poorly
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suited for particular purposes.</para>
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</epigraph>
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<para>A working knowledge of shell scripting is essential to anyone
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|
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@ -737,7 +747,7 @@ exit $WHATEVER # Doesn't matter. The script will not exit here.</programlisting
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prolog tests whether the script has been invoked with the correct
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number of parameters.</para>
|
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|
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<para><programlisting>if [ $# -ne $Number_of_expected args ]
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<para><programlisting>if [ $# -ne $Number_of_expected_args ]
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then
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echo "Usage: `basename $0` script_parameters"
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exit $E_WRONG_ARGS
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|
|
@ -3133,7 +3143,11 @@ arch=$(uname -m)</programlisting></para>
|
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linkend="varrefnew">indirect referencing</link>.</para>
|
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<para><programlisting>args=$# # Number of args passed.
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lastarg=${!args} # Note that lastarg=${!$#} doesn't work.</programlisting></para>
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lastarg=${!args}
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# Or: lastarg=${!#}
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# (Thanks, Chris Monson.)
|
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# Note that lastarg=${!$#} doesn't work.
|
||||
</programlisting></para>
|
||||
|
||||
|
||||
<para>Some scripts can perform different operations,
|
||||
|
|
@ -8057,6 +8071,33 @@ echo "n = $n" # n = 2</programlisting></para>
|
|||
<programlisting>&indref;</programlisting>
|
||||
</example>
|
||||
|
||||
|
||||
<para>
|
||||
Nils Radtke shows how to build <quote>dynamic</quote>
|
||||
variable names and evaluate their contents. This can be useful
|
||||
when <link linkend="sourceref">sourcing</link> configuration files.
|
||||
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||||
<programlisting>#!/bin/bash
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# ---------------------------------------------
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# This could be "sourced" from a separate file.
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isdnMyProviderRemoteNet=172.16.0.100
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isdnYourProviderRemoteNet=10.0.0.10
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isdnOnlineService="MyProvider"
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# ---------------------------------------------
|
||||
|
||||
|
||||
remoteNet=$(eval "echo \$$(echo isdn${isdnOnlineService}RemoteNet)")
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remoteNet=$(eval "echo \$$(echo isdnMyProviderRemoteNet)")
|
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remoteNet=$(eval "echo \$isdnMyProviderRemoteNet")
|
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remoteNet=$(eval "echo $isdnMyProviderRemoteNet")
|
||||
|
||||
echo "$remoteNet" # 172.16.0.100</programlisting>
|
||||
</para>
|
||||
|
||||
|
||||
|
||||
<example id="coltotaler2">
|
||||
<title>Passing an indirect reference to <replaceable>awk</replaceable></title>
|
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<programlisting>&coltotaler2;</programlisting>
|
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|
|
@ -8084,10 +8125,21 @@ echo "n = $n" # n = 2</programlisting></para>
|
|||
<secondary>$RANDOM</secondary>
|
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</indexterm>
|
||||
<title>$RANDOM: generate random integer</title>
|
||||
<para>$RANDOM is an internal Bash function (not a constant) that
|
||||
returns a <emphasis>pseudorandom</emphasis> integer in the range
|
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0 - 32767. $RANDOM should <replaceable>not</replaceable> be used
|
||||
to generate an encryption key.</para>
|
||||
<para>$RANDOM is an internal Bash <link
|
||||
linkend="functionref">function</link> (not a constant) that
|
||||
returns a <emphasis>pseudorandom</emphasis>
|
||||
|
||||
<footnote><para>True <quote>randomness,</quote> insofar as
|
||||
it exists at all, is only to be found in certain
|
||||
incompletely understood natural phenomena such as
|
||||
radioactive decay. Computers can only simulate
|
||||
randomness, and computer-generated sequences of
|
||||
<quote>random</quote> numbers are therefore referred to as
|
||||
<emphasis>pseudorandom.</emphasis></para></footnote>
|
||||
|
||||
integer in the range 0 - 32767. $RANDOM should
|
||||
<replaceable>not</replaceable> be used to generate an encryption
|
||||
key.</para>
|
||||
|
||||
<example id="ex21">
|
||||
<title>Generating random numbers</title>
|
||||
|
|
@ -8164,10 +8216,10 @@ rnumber=$(((RANDOM%30/3+1)*3))
|
|||
pseudorandom numbers than the <varname>$RANDOM</varname>
|
||||
variable. <userinput>dd if=/dev/urandom of=targetfile
|
||||
bs=1 count=XX</userinput> creates a file of well-scattered
|
||||
pseudorandom numbers. However, assigning these numbers
|
||||
to a variable in a script requires a workaround, such as
|
||||
filtering through <link linkend="odref">od</link> (as in
|
||||
above example) or using <link linkend="ddref">dd</link>
|
||||
pseudorandom numbers. However, assigning these numbers to a
|
||||
variable in a script requires a workaround, such as filtering
|
||||
through <link linkend="odref">od</link> (as in above example and
|
||||
<xref linkend="rnd">) or using <link linkend="ddref">dd</link>
|
||||
(see <xref linkend="blotout">).</para>
|
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|
||||
<para><anchor id="awkrandomref"></para>
|
||||
|
|
@ -11136,16 +11188,17 @@ find "$DIR" -type f -atime +5 -exec rm {} \;
|
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<para><programlisting>find /etc -exec grep '[0-9][0-9]*[.][0-9][0-9]*[.][0-9][0-9]*[.][0-9][0-9]*' {} \;
|
||||
|
||||
# Finds all IP addresses (xxx.xxx.xxx.xxx) in /etc directory files.
|
||||
# There a few extraneous hits - how can they be filtered out?
|
||||
# There a few extraneous hits. How can they be filtered out?
|
||||
|
||||
# Perhaps by:
|
||||
|
||||
find /etc -type f -exec cat '{}' \; | tr -c '.[:digit:]' '\n' \
|
||||
| grep '^[^.][^.]*\.[^.][^.]*\.[^.][^.]*\.[^.][^.]*$'
|
||||
# [:digit:] is one of the character classes
|
||||
# introduced with the POSIX 1003.2 standard.
|
||||
| grep '^[^.][^.]*\.[^.][^.]*\.[^.][^.]*\.[^.][^.]*$'
|
||||
#
|
||||
# [:digit:] is one of the character classes
|
||||
#+ introduced with the POSIX 1003.2 standard.
|
||||
|
||||
# Thanks, S.C.
|
||||
# Thanks, Stephane Chazelas.
|
||||
</programlisting></para>
|
||||
|
||||
|
||||
|
|
@ -12216,18 +12269,20 @@ fi</programlisting>
|
|||
<programlisting>&grp;</programlisting>
|
||||
</example>
|
||||
|
||||
<para>How can <command>grep</command> search for two separate
|
||||
patterns? What if you want <command>grep</command> to display
|
||||
all lines in a file or files that contain
|
||||
both <quote>pattern1</quote> <emphasis>and</emphasis>
|
||||
<quote>pattern2</quote>?</para>
|
||||
<para>How can <command>grep</command> search for two (or
|
||||
more) separate patterns? What if you want
|
||||
<command>grep</command> to display all lines in a file
|
||||
or files that contain both <quote>pattern1</quote>
|
||||
<emphasis>and</emphasis> <quote>pattern2</quote>?</para>
|
||||
|
||||
<para>One method of accomplishing this is to <link
|
||||
<para>One method is to <link
|
||||
linkend="piperef">pipe</link> the result of <command>grep
|
||||
pattern1</command> to <command>grep pattern2</command>.</para>
|
||||
|
||||
<para>For example, given the following file:</para>
|
||||
|
||||
<para>
|
||||
<programlisting># tstfile
|
||||
<programlisting># Filename: tstfile
|
||||
|
||||
This is a sample file.
|
||||
This is an ordinary text file.
|
||||
|
|
@ -12236,8 +12291,12 @@ This file is not unusual.
|
|||
Here is some text.</programlisting>
|
||||
</para>
|
||||
|
||||
<para>Now, let's search this file for lines containing
|
||||
<emphasis>both</emphasis> <quote>file</quote> and
|
||||
<quote>test</quote> . . . </para>
|
||||
|
||||
<screen><prompt>bash$ </prompt><userinput>grep file tstfile</userinput>
|
||||
<computeroutput># tstfile
|
||||
<computeroutput># Filename: tstfile
|
||||
This is a sample file.
|
||||
This is an ordinary text file.
|
||||
This file does not contain any unusual text.
|
||||
|
|
@ -12247,6 +12306,8 @@ Here is some text.</programlisting>
|
|||
<computeroutput>This is an ordinary text file.
|
||||
This file does not contain any unusual text.</computeroutput></screen>
|
||||
|
||||
<para>--</para>
|
||||
|
||||
<note>
|
||||
<para><anchor id="egrepref"><command>egrep</command>
|
||||
(<emphasis>extended grep</emphasis>) is the same
|
||||
|
|
@ -12258,7 +12319,7 @@ Here is some text.</programlisting>
|
|||
<para><command>fgrep</command> (<emphasis>fast
|
||||
grep</emphasis>) is the same as <command>grep
|
||||
-F</command>. It does a literal string search (no regular
|
||||
expressions), which allegedly speeds things up a bit.</para>
|
||||
expressions), which usually speeds things up a bit.</para>
|
||||
|
||||
<para><command>agrep</command> (<emphasis>approximate
|
||||
grep</emphasis>) extends the capabilities of
|
||||
|
|
@ -12845,7 +12906,7 @@ tr -d 0-9 <filename
|
|||
is <command>groff</command>. This is the enhanced GNU version
|
||||
of the venerable UNIX <command>roff/troff</command> display
|
||||
and typesetting package. <emphasis>Manpages</emphasis>
|
||||
use <command>groff</command> (see <xref linkend="manview">).</para>
|
||||
use <command>groff</command>.</para>
|
||||
|
||||
<para>The <command>tbl</command> table processing utility
|
||||
is considered part of <command>groff</command>, as its
|
||||
|
|
@ -12857,9 +12918,16 @@ tr -d 0-9 <filename
|
|||
its function is to convert equation markup into
|
||||
<command>groff</command> commands.</para>
|
||||
|
||||
<example id="manview">
|
||||
<title><command>manview</command>: Viewing formatted manpages
|
||||
</title>
|
||||
<programlisting>&manview;</programlisting>
|
||||
</example>
|
||||
|
||||
</listitem>
|
||||
</varlistentry>
|
||||
|
||||
|
||||
<varlistentry>
|
||||
<term><command>lex</command></term>
|
||||
<term><command>yacc</command></term>
|
||||
|
|
@ -13368,6 +13436,24 @@ tr -d 0-9 <filename
|
|||
</screen>
|
||||
</para>
|
||||
|
||||
<para>
|
||||
<programlisting># Find sh and Bash scripts in a given directory:
|
||||
|
||||
DIRECTORY=/usrlocal/bin
|
||||
KEYWORD=Bourne
|
||||
# Bourne and Bourne-Again shell scripts
|
||||
|
||||
file $DIRECTORY/* | fgrep $KEYWORD
|
||||
|
||||
# Output:
|
||||
|
||||
# /usr/local/bin/burn-cd: Bourne-Again shell script text executable
|
||||
# /usr/local/bin/burnit: Bourne-Again shell script text executable
|
||||
# /usr/local/bin/cassette.sh: Bourne shell script text executable
|
||||
# /usr/local/bin/copy-cd: Bourne-Again shell script text executable
|
||||
# . . .</programlisting>
|
||||
</para>
|
||||
|
||||
<example id="stripc">
|
||||
<title>Stripping comments from C program files</title>
|
||||
<programlisting>&stripc;</programlisting>
|
||||
|
|
@ -14675,7 +14761,7 @@ echo "tempfile name = $tempfile"
|
|||
</varlistentry>
|
||||
|
||||
<varlistentry>
|
||||
<term><command>wget</command></term>
|
||||
<term><anchor id="wgetref"><command>wget</command></term>
|
||||
<indexterm>
|
||||
<primary>wget</primary>
|
||||
</indexterm>
|
||||
|
|
@ -14697,6 +14783,8 @@ wget -r ftp://ftp.xyz24.net/~bozo/project_files/ -O $SAVEFILE</programlisting>
|
|||
<programlisting>"efetch;</programlisting>
|
||||
</example>
|
||||
|
||||
<para>See also <xref linkend="wgetter2">.</para>
|
||||
|
||||
</listitem>
|
||||
</varlistentry>
|
||||
|
||||
|
|
@ -14793,6 +14881,18 @@ wget -r ftp://ftp.xyz24.net/~bozo/project_files/ -O $SAVEFILE</programlisting>
|
|||
<programlisting>&remote;</programlisting>
|
||||
</example>
|
||||
|
||||
<caution>
|
||||
<para>Within a loop, <command>ssh</command> may cause
|
||||
unexpected behavior. According to a <ulink
|
||||
url="http://groups-beta.google.com/group/comp.unix.shell/msg/dcb446b5fff7d230">
|
||||
Usenet post</ulink> in the comp.unix shell archives,
|
||||
<command>ssh</command> inherits the loop's
|
||||
<filename>stdin</filename>. To remedy this, pass
|
||||
<command>ssh</command> either the <option>-n</option>
|
||||
or <option>-f</option> option.</para>
|
||||
<para>Thanks, Jason Bechtel, for pointing this out.</para>
|
||||
</caution>
|
||||
|
||||
</listitem>
|
||||
</varlistentry>
|
||||
|
||||
|
|
@ -16316,9 +16416,23 @@ sudo cp /root/secretfile /home/bozo/secret
|
|||
<secondary>logged in</secondary>
|
||||
</indexterm>
|
||||
<listitem>
|
||||
|
||||
<para>List <emphasis>last</emphasis> logged in users, as read from
|
||||
<filename>/var/log/wtmp</filename>. This command can also
|
||||
show remote logins.</para>
|
||||
|
||||
<para>For example, to show the last few times the system
|
||||
rebooted:</para>
|
||||
|
||||
<screen><prompt>bash$ </prompt><userinput>last reboot</userinput>
|
||||
<computeroutput>reboot system boot 2.6.9-1.667 Fri Feb 4 18:18 (00:02)
|
||||
reboot system boot 2.6.9-1.667 Fri Feb 4 15:20 (01:27)
|
||||
reboot system boot 2.6.9-1.667 Fri Feb 4 12:56 (00:49)
|
||||
reboot system boot 2.6.9-1.667 Thu Feb 3 21:08 (02:17)
|
||||
. . .
|
||||
|
||||
wtmp begins Tue Feb 1 12:50:09 2005</computeroutput></screen>
|
||||
|
||||
</listitem>
|
||||
</varlistentry>
|
||||
|
||||
|
|
@ -16729,7 +16843,7 @@ setserial /dev/$DEVICE irq 0 ; setserial /dev/$DEVICE irq $IRQ</programlisting><
|
|||
</varlistentry>
|
||||
|
||||
<varlistentry>
|
||||
<term><command>lastlog</command></term>
|
||||
<term><anchor id="lastlogref"><command>lastlog</command></term>
|
||||
<indexterm>
|
||||
<primary>lastlog</primary>
|
||||
</indexterm>
|
||||
|
|
@ -17655,7 +17769,8 @@ Average: all 6.33 1.70 14.71 0.00 77.26</compute
|
|||
<secondary>ifconfig</secondary>
|
||||
</indexterm>
|
||||
<listitem>
|
||||
<para>Network interface configuration and tuning utility.</para>
|
||||
<para>Network <emphasis>interface configuration</emphasis>
|
||||
and tuning utility.</para>
|
||||
|
||||
<screen><prompt>bash$ </prompt><userinput>ifconfig -a</userinput>
|
||||
<computeroutput>lo Link encap:Local Loopback
|
||||
|
|
@ -19972,19 +20087,41 @@ echo "This line had better not echo." # Follows an 'exit' command.</programlist
|
|||
<sect1><title>A Brief Introduction to Regular Expressions</title>
|
||||
|
||||
<para>An expression is a string of characters. Those characters
|
||||
that have an interpretation above and beyond their literal
|
||||
having an interpretation above and beyond their literal
|
||||
meaning are called <emphasis>metacharacters</emphasis>. A
|
||||
quote symbol, for example, may denote speech by a person,
|
||||
<emphasis>ditto</emphasis>, or a meta-meaning for the symbols
|
||||
that follow. Regular Expressions are sets of characters and/or
|
||||
metacharacters that an operating system endows with special
|
||||
features.
|
||||
metacharacters that match (or specify) patterns.</para>
|
||||
|
||||
<para>A Regular Expression contains one or more of the
|
||||
following:</para>
|
||||
|
||||
<footnote><para>The simplest type of Regular Expression is a
|
||||
character string that retains its literal meaning, not
|
||||
containing any metacharacters.</para></footnote>
|
||||
<itemizedlist>
|
||||
|
||||
<listitem>
|
||||
<para>A character set. These are the characters retaining their
|
||||
literal meaning. The simplest type of Regular Expression
|
||||
consists <emphasis>only</emphasis> of a character set, with no
|
||||
metacharacters.</para>
|
||||
</listitem>
|
||||
|
||||
<listitem>
|
||||
<para>An anchor. These designate (<emphasis>anchor</emphasis>)
|
||||
the position in the line of text that the RE is to
|
||||
match. For example, <token>^</token>, and <token>$</token>
|
||||
are anchors.</para>
|
||||
</listitem>
|
||||
|
||||
<listitem>
|
||||
<para>Modifiers. These expand or narrow
|
||||
(<emphasis>modify</emphasis>) the range of text the RE is
|
||||
to match. Modifiers include the asterisk, brackets, and
|
||||
the backslash.</para>
|
||||
</listitem>
|
||||
|
||||
</itemizedlist>
|
||||
|
||||
</para>
|
||||
|
||||
<para>The main uses for Regular Expressions (REs) are text
|
||||
searches and string manipulation. An RE
|
||||
|
|
@ -20091,9 +20228,6 @@ exit 0</programlisting></para></footnote>
|
|||
<para>The dollar sign -- <token>$</token> -- at the end of an
|
||||
RE matches the end of a line.</para>
|
||||
<para><quote>^$</quote> matches blank lines.</para>
|
||||
<note><para>The <token>^</token> and <token>$</token> are known as
|
||||
<emphasis>anchors</emphasis>, since they indicate or anchor a
|
||||
position within an RE.</para></note>
|
||||
</listitem>
|
||||
|
||||
<listitem>
|
||||
|
|
@ -20244,9 +20378,10 @@ This line contains no numbers at all. # No match.</programlisting></para>
|
|||
<formalpara>
|
||||
<title><anchor id="extregex">Extended REs</title>
|
||||
|
||||
<para>Used in <link linkend="egrepref">egrep</link>,
|
||||
<para>Additional metacharacters added to the basic set. Used
|
||||
in <link linkend="egrepref">egrep</link>,
|
||||
<link linkend="awkref">awk</link>, and <link
|
||||
linkend="perlref">Perl</link></para>
|
||||
linkend="perlref">Perl</link>.</para>
|
||||
|
||||
</formalpara>
|
||||
</listitem>
|
||||
|
|
@ -21320,6 +21455,15 @@ exit # Invokes "exit ()" function, not "exit" builtin.
|
|||
command works on arguments passed to functions (see <xref
|
||||
linkend="multiplication">).</para></important>
|
||||
|
||||
<para>But, what about command-line arguments passed to the script?
|
||||
Does a function see them? Well, let's clear up the confusion.</para>
|
||||
|
||||
<example id="funccmdlinearg">
|
||||
<title>Functions and command-line args passed to the script</title>
|
||||
<programlisting>&funccmdlinearg;</programlisting>
|
||||
</example>
|
||||
|
||||
|
||||
<para>In contrast to certain other programming languages,
|
||||
shell scripts normally pass only value parameters to
|
||||
functions. Variable names (which are actually pointers), if
|
||||
|
|
@ -21649,7 +21793,7 @@ echo "global_var = $global_var" # global_var = 37
|
|||
|
||||
recursive_function ()
|
||||
{
|
||||
(( $1 < $2 )) && f $(( $1 + 1 )) $2;
|
||||
(( $1 < $2 )) && recursive_function $(( $1 + 1 )) $2;
|
||||
# As long as 1st parameter is less than 2nd,
|
||||
#+ increment 1st and recurse.
|
||||
}
|
||||
|
|
@ -22376,6 +22520,8 @@ exit 0</programlisting></para>
|
|||
then, as root, <command>mkdir /mnt/flashdrive</command>.</para>
|
||||
<para>To actually mount the drive, use the following command:
|
||||
<command>mount /mnt/flashdrive</command></para>
|
||||
<para>Newer Linux distros automount flash drives in the
|
||||
<filename class="directory">/media</filename> directory.</para>
|
||||
</footnote>
|
||||
|
||||
<programlisting>/dev/sda1 /mnt/flashdrive auto noauto,user,noatime 0 0</programlisting>
|
||||
|
|
@ -22406,7 +22552,7 @@ exit 0</programlisting></para>
|
|||
<para>[Mark contributed the above example.]</para>
|
||||
|
||||
<para>Downloading a URL:</para>
|
||||
<screen><prompt>bash$ </prompt><userinput>exec 5<>/dev/tcp/www.slashdot.org/80</userinput>
|
||||
<screen><prompt>bash$ </prompt><userinput>exec 5<>/dev/tcp/www.net.cn/80</userinput>
|
||||
<prompt>bash$ </prompt><userinput>echo -e "GET / HTTP/1.0\n" >&5</userinput>
|
||||
<prompt>bash$ </prompt><userinput>cat <&5</userinput>
|
||||
</screen>
|
||||
|
|
@ -23199,9 +23345,13 @@ echo $_ # $_ is a special variable set to last arg of last command.
|
|||
xyz((!*=value2 # Causes severe problems.</programlisting>
|
||||
</para>
|
||||
|
||||
<para>Using a hyphen or other reserved characters in a variable name.
|
||||
<para>Using a hyphen or other reserved characters in a variable name (or
|
||||
function name).
|
||||
<programlisting>var-1=23
|
||||
# Use 'var_1' instead.</programlisting>
|
||||
# Use 'var_1' instead.
|
||||
|
||||
function-whatever ()
|
||||
# Use 'function_whatever ()' instead.</programlisting>
|
||||
</para>
|
||||
|
||||
<para>Using the same name for a variable and a function. This can make a
|
||||
|
|
@ -23499,8 +23649,10 @@ find $HOME -type f -atime +30 -size 100k | {
|
|||
# The "error.log" file will not have anything written to it.</programlisting>
|
||||
</para>
|
||||
|
||||
|
||||
<para>--</para>
|
||||
|
||||
|
||||
<para>Using <quote>suid</quote> commands within scripts is risky,
|
||||
as it may compromise system security.
|
||||
<footnote><para>Setting the <emphasis>suid</emphasis> permission on
|
||||
|
|
@ -24207,6 +24359,9 @@ test "$city" \< Paris && echo "Yes, Paris is greater than $city" # Greater ASCI
|
|||
substitutes a clean and logical syntax for the clumsy constructs
|
||||
just discussed.</para>
|
||||
|
||||
<para>Henry/teikedvl has likewise created a utility (<ulink
|
||||
url="http://scriptechocolor.sourceforge.net/">http://scriptechocolor.sourceforge.net/</ulink>) to simplify creation of colorized scripts.</para>
|
||||
|
||||
|
||||
</sect1> <!-- "Colorizing" scripts -->
|
||||
|
||||
|
|
@ -25093,14 +25248,15 @@ fi</programlisting>
|
|||
professor. Crazy as a loon, the fellow was. At the sight of a
|
||||
book, any book -- at the library, at a bookstore, anywhere --
|
||||
he would become totally obsessed with the idea that he could have
|
||||
written it, should have written it, and done a better job of it to
|
||||
boot. He would thereupon rush home and proceed to do just that,
|
||||
written it, should have written it -- and done a better job of it
|
||||
to boot. He would thereupon rush home and proceed to do just that,
|
||||
write a book with the very same title. When he died some years
|
||||
later, he allegedly had several thousand books to his credit,
|
||||
probably putting even Asimov to shame. The books might not have
|
||||
been any good -- who knows -- but does that really matter? Here's
|
||||
a fellow who lived his dream, even if he was obsessed by it,
|
||||
driven by it, and I can't help admiring the old coot...</para>
|
||||
driven by it . . . and somehow I can't help admiring the old
|
||||
coot.</para>
|
||||
|
||||
</sect1> <!-- Author's Note -->
|
||||
|
||||
|
|
@ -25129,7 +25285,7 @@ fi</programlisting>
|
|||
mortgage calculator, the <ulink
|
||||
url="http://ibiblio.org/pub/Linux/games/amusements/judge-1.0.tar.gz">judge</ulink>
|
||||
Scrabble® adjudicator, and the <ulink
|
||||
url="http://ibiblio.org/pub/Linux/libs/yawl-0.3.tar.gz">yawl</ulink>
|
||||
url="http://ibiblio.org/pub/Linux/libs/yawl-0.3.2.tar.gz">yawl</ulink>
|
||||
word gaming list package. He got his start in programming using
|
||||
FORTRAN IV on a CDC 3800, but is not the least bit nostalgic
|
||||
for those days.</para>
|
||||
|
|
@ -25308,22 +25464,23 @@ fi</programlisting>
|
|||
<para>Others contributing scripts, making helpful suggestions, and
|
||||
pointing out errors were Gabor Kiss, Leopold Toetsch, Peter
|
||||
Tillier, Marcus Berglof, Tony Richardson, Nick Drage (script
|
||||
ideas!), Rich Bartell, Jess Thrysoee, Adam Lazur, Bram Moolenaar,
|
||||
Baris Cicek, Greg Keraunen, Keith Matthews, Sandro Magi, Albert
|
||||
Reiner, Dim Segebart, Rory Winston, Lee Bigelow, Wayne Pollock,
|
||||
<quote>jipe,</quote> <quote>Mark,</quote> <quote>bojster,</quote>
|
||||
<quote>Ender</quote>, Emilio Conti, Ian. D. Allen, Arun
|
||||
Giridhar, Dennis Leeuw, Dan Jacobson, Aurelio Marinho Jargas,
|
||||
Edward Scholtz, Jean Helou, Chris Martin, Lee Maschmeyer,
|
||||
Bruno Haible, Wilbert Berendsen, Sebastien Godard, Bjön
|
||||
Eriksson, <quote>nyal,</quote> John MacDonald, Joshua Tschida,
|
||||
Troy Engel, Manfred Schwarb, Amit Singh, Bill Gradwohl, David
|
||||
Lombard, Jason Parker, Steve Parker, Bruce W. Clare, William
|
||||
Park, Vernia Damiano, Mihai Maties, Jeremy Impson, Ken Fuchs,
|
||||
Frank Wang, Sylvain Fourmanoit, Matthew Walker, Kenny Stauffer,
|
||||
Filip Moritz, Andrzej Stefanski, Daniel Albers, Stefano Palmeri,
|
||||
Alfredo Pironti, and David Lawyer (himself an author of four
|
||||
HOWTOs).</para>
|
||||
ideas!), Rich Bartell, Jess Thrysoee, Adam Lazur, Bram
|
||||
Moolenaar, Baris Cicek, Greg Keraunen, Keith Matthews, Sandro
|
||||
Magi, Albert Reiner, Dim Segebart, Rory Winston, Lee Bigelow,
|
||||
Wayne Pollock, <quote>jipe,</quote> <quote>Mark,</quote>
|
||||
<quote>bojster,</quote> <quote>Ender</quote>, Emilio Conti,
|
||||
Ian. D. Allen, Arun Giridhar, Dennis Leeuw, Dan Jacobson, Aurelio
|
||||
Marinho Jargas, Edward Scholtz, Jean Helou, Chris Martin, Lee
|
||||
Maschmeyer, Bruno Haible, Wilbert Berendsen, Sebastien Godard,
|
||||
Bjön Eriksson, <quote>nyal,</quote> John MacDonald, Joshua
|
||||
Tschida, Troy Engel, Manfred Schwarb, Amit Singh, Bill Gradwohl,
|
||||
David Lombard, Jason Parker, Steve Parker, Bruce W. Clare,
|
||||
William Park, Vernia Damiano, Mihai Maties, Jeremy Impson,
|
||||
Ken Fuchs, Frank Wang, Sylvain Fourmanoit, Matthew Walker,
|
||||
Kenny Stauffer, Filip Moritz, Andrzej Stefanski, Daniel Albers,
|
||||
Stefano Palmeri, Nils Radtke, Jeroen Domburg, Alfredo Pironti,
|
||||
Phil Braham, <quote>Little Monster</quote> (Alexis), 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 <command>Bash</command>,
|
||||
|
|
@ -25858,6 +26015,13 @@ fi</programlisting>
|
|||
</abstract>
|
||||
</biblioentry>
|
||||
|
||||
<biblioentry>
|
||||
<abstract>
|
||||
<para>Example shell scripts at <ulink
|
||||
url="http://www.zazzybob.com">zazzybob</ulink>.</para>
|
||||
</abstract>
|
||||
</biblioentry>
|
||||
|
||||
<biblioentry>
|
||||
<abstract>
|
||||
<para>Steve Parker's <ulink
|
||||
|
|
@ -25874,6 +26038,14 @@ fi</programlisting>
|
|||
</abstract>
|
||||
</biblioentry>
|
||||
|
||||
<biblioentry>
|
||||
<abstract>
|
||||
<para><quote>Mini-scripts</quote> at <ulink
|
||||
url="http://www.primaat.com/unix_oneliners">Unix
|
||||
Oneliners</ulink>.</para>
|
||||
</abstract>
|
||||
</biblioentry>
|
||||
|
||||
<biblioentry>
|
||||
<abstract>
|
||||
<para>Giles Orr's <ulink
|
||||
|
|
@ -25986,7 +26158,11 @@ fi</programlisting>
|
|||
url="http://linuxgazette.net/108/park.html">article</ulink>
|
||||
in the November, 2004 issue of the <ulink
|
||||
url="http://www.linuxgazette.net">Linux Gazette</ulink> on
|
||||
adding string functions to Bash.</para>
|
||||
adding string functions to Bash, with a <ulink
|
||||
url="http://linuxgazette.net/109/park.html">followup article</ulink>
|
||||
in the December issue, and <ulink
|
||||
url="http://linuxgazette.net/110/park.htm">yet another</ulink> in
|
||||
the January, 2005 issue.</para>
|
||||
</abstract>
|
||||
|
||||
</biblioentry>
|
||||
|
|
@ -26063,12 +26239,6 @@ fi</programlisting>
|
|||
illustrate some interesting shell programming techniques. They are useful,
|
||||
too. Have fun analyzing and running them.</para>
|
||||
|
||||
<example id="manview">
|
||||
<title><command>manview</command>: Viewing formatted manpages
|
||||
</title>
|
||||
<programlisting>&manview;</programlisting>
|
||||
</example>
|
||||
|
||||
<example id="mailformat">
|
||||
<title><command>mailformat</command>: Formatting an e-mail message</title>
|
||||
<programlisting>&mailformat;</programlisting>
|
||||
|
|
@ -26254,13 +26424,21 @@ fi</programlisting>
|
|||
</example>
|
||||
|
||||
|
||||
<para>This powerful script helps hunt down spammers .</para>
|
||||
<para>This powerful script helps hunt down spammers.</para>
|
||||
|
||||
<example id="isspammer2">
|
||||
<title>Spammer Identification</title>
|
||||
<programlisting>&isspammer2;</programlisting>
|
||||
</example>
|
||||
|
||||
<para><quote>Little Monster's</quote> front end to <link
|
||||
linkend="wgetref">wget</link>.</para>
|
||||
|
||||
<example id="wgetter2">
|
||||
<title>Making <command>wget</command> easier to use</title>
|
||||
<programlisting>&wgetter2;</programlisting>
|
||||
</example>
|
||||
|
||||
<para>To end this section, a review of the basics . . . and more.</para>
|
||||
|
||||
<example id="basicsreviewed">
|
||||
|
|
@ -26268,6 +26446,11 @@ fi</programlisting>
|
|||
<programlisting>&basicsreviewed;</programlisting>
|
||||
</example>
|
||||
|
||||
<example id="cdll">
|
||||
<title>An expanded <command>cd</command> command</title>
|
||||
<programlisting>&cdll;</programlisting>
|
||||
</example>
|
||||
|
||||
</appendix>
|
||||
<!-- End Contributed Scripts appendix -->
|
||||
|
||||
|
|
@ -27731,7 +27914,6 @@ exit 0</programlisting>
|
|||
and utilities (such as <command>fsck</command>).</para>
|
||||
</listitem>
|
||||
|
||||
|
||||
<listitem>
|
||||
<para><filename class="directory">/usr/sbin</filename></para>
|
||||
<para>More system administrative programs and utilities.</para>
|
||||
|
|
@ -27760,15 +27942,40 @@ exit 0</programlisting>
|
|||
</listitem>
|
||||
|
||||
<listitem>
|
||||
<para><filename class="directory">/tmp</filename></para>
|
||||
<para>System temporary files.</para>
|
||||
<para><filename class="directory">/dev</filename></para>
|
||||
<para>Device directory. Entries (but <emphasis>not</emphasis>
|
||||
mount points) for physical and virtual devices.
|
||||
See <xref linkend="devproc">.</para>
|
||||
</listitem>
|
||||
|
||||
<listitem>
|
||||
<para><filename class="directory">/proc</filename></para>
|
||||
<para>Process directory. Contains information and statistics
|
||||
about running processes and kernel parameters.
|
||||
See <xref linkend="devproc">.</para>
|
||||
</listitem>
|
||||
|
||||
<listitem>
|
||||
<para><filename class="directory">/sys</filename></para>
|
||||
<para>Systemwide process directory. Contains information and
|
||||
statistics about running processes. This is newly added to Linux
|
||||
with the 2.6.X kernels.</para>
|
||||
<para>Systemwide device directory. Contains information and
|
||||
statistics about device and device names. This is newly
|
||||
added to Linux with the 2.6.X kernels.</para>
|
||||
</listitem>
|
||||
|
||||
<listitem>
|
||||
<para><filename class="directory">/mnt</filename></para>
|
||||
<para><emphasis>Mount</emphasis>. Directory for mounting
|
||||
hard drive partitions, such as <filename
|
||||
class="directory">/mnt/dos</filename>, and physical
|
||||
devices. In newer Linux distros, the <filename
|
||||
class="directory">/media</filename> directory has taken
|
||||
over as the preferred mount point for I/O devices.</para>
|
||||
</listitem>
|
||||
|
||||
<listitem>
|
||||
<para><filename class="directory">/media</filename></para>
|
||||
<para>In newer Linux distros, the preferred mount point for
|
||||
I/O devices, such as CD ROMs or USB flash drives.</para>
|
||||
</listitem>
|
||||
|
||||
<listitem>
|
||||
|
|
@ -27799,6 +28006,11 @@ exit 0</programlisting>
|
|||
<para>More systemwide library files.</para>
|
||||
</listitem>
|
||||
|
||||
<listitem>
|
||||
<para><filename class="directory">/tmp</filename></para>
|
||||
<para>System temporary files.</para>
|
||||
</listitem>
|
||||
|
||||
<listitem>
|
||||
<para><filename class="directory">/boot</filename></para>
|
||||
<para>System <emphasis>boot</emphasis> directory. The kernel,
|
||||
|
|
@ -27845,9 +28057,13 @@ error()
|
|||
exit $E_CDERROR
|
||||
}
|
||||
|
||||
cd $var || error "`eval_gettext \"Can\'t cd to \$var.\"`"
|
||||
cd $var || error "`eval_gettext \"Can\'t cd to \\\$var.\"`"
|
||||
# The triple backslashes (escapes) in front of $var needed
|
||||
#+ "because eval_gettext expects a string
|
||||
#+ where the variable values have not yet been substituted."
|
||||
# -- per Bruno Haible
|
||||
read -p "`gettext \"Enter the value: \"`" var
|
||||
# ...
|
||||
# ...
|
||||
|
||||
|
||||
# ------------------------------------------------------------------
|
||||
|
|
@ -28593,6 +28809,23 @@ exit 0</programlisting>
|
|||
|
||||
<para>---</para>
|
||||
|
||||
<para>Explain what the following script does. It is really just
|
||||
a parameterized command-line pipe.</para>
|
||||
|
||||
<para>
|
||||
<programlisting>#!/bin/bash
|
||||
|
||||
DIRNAME=/usr/bin
|
||||
FILETYPE="shell script"
|
||||
LOGFILE=logfile
|
||||
|
||||
file "$DIRNAME"/* | fgrep "$FILETYPE" | tee $LOGFILE | wc -l
|
||||
|
||||
exit 0</programlisting>
|
||||
</para>
|
||||
|
||||
<para>---</para>
|
||||
|
||||
<para>A reader sent in the following code snippet.
|
||||
|
||||
<programlisting>while read LINE
|
||||
|
|
@ -28638,7 +28871,7 @@ done < `tail -f /var/log/messages`</programlisting>
|
|||
|
||||
|
||||
<variablelist id="exeasy">
|
||||
<title><anchor id="exeasy1">Easy</title>
|
||||
<title><anchor id="exeasy1">EASY</title>
|
||||
|
||||
<varlistentry>
|
||||
<term><command>Home Directory Listing</command></term>
|
||||
|
|
@ -28766,7 +28999,21 @@ done < `tail -f /var/log/messages`</programlisting>
|
|||
|
||||
|
||||
<variablelist id="exmedium">
|
||||
<title><anchor id="exmedium1">Intermediate</title>
|
||||
<title><anchor id="exmedium1">INTERMEDIATE</title>
|
||||
|
||||
<varlistentry>
|
||||
<term><command>Integer or String</command></term>
|
||||
<listitem>
|
||||
<para>Write a script <link linkend="functionref">function</link>
|
||||
that determines if an argument passed to it is an integer
|
||||
or a string. The function will return TRUE (0) if
|
||||
passed an integer, and FALSE (1) if passed a string.</para>
|
||||
<para>Hint: What does the following expression return
|
||||
when <varname>$1</varname> is <emphasis>not</emphasis> an
|
||||
integer?</para>
|
||||
<para><varname>expr $1 + 0</varname></para>
|
||||
</listitem>
|
||||
</varlistentry>
|
||||
|
||||
<varlistentry>
|
||||
<term><command>Managing Disk Space</command></term>
|
||||
|
|
@ -28780,6 +29027,20 @@ done < `tail -f /var/log/messages`</programlisting>
|
|||
</listitem>
|
||||
</varlistentry>
|
||||
|
||||
<varlistentry>
|
||||
<term><command>Logged in User Information</command></term>
|
||||
<listitem>
|
||||
|
||||
<para>For all logged in users, show their real names and the time
|
||||
and date of their last login.</para>
|
||||
|
||||
<para>Hint: use <link linkend="whoref">who</link>,
|
||||
<link linkend="lastlogref">lastlog</link>,
|
||||
and parse <filename>/etc/passwd</filename>.</para>
|
||||
|
||||
</listitem>
|
||||
</varlistentry>
|
||||
|
||||
<varlistentry>
|
||||
<term><command>Safe Delete</command></term>
|
||||
<listitem>
|
||||
|
|
@ -28929,7 +29190,7 @@ Smith,Tom,404 Polk Ave.,Los Angeles,CA,90003,(213) 879-5612
|
|||
|
||||
|
||||
<variablelist id="exdifficult">
|
||||
<title><anchor id="exdifficult1">Difficult</title>
|
||||
<title><anchor id="exdifficult1">DIFFICULT</title>
|
||||
|
||||
<varlistentry>
|
||||
<term><command>Testing Passwords</command></term>
|
||||
|
|
@ -29549,6 +29810,11 @@ fairly detailed rundown on the Playfair Cipher and its solution methods.</progra
|
|||
<entry>14 Nov 2004</entry>
|
||||
<entry>BAYBERRY release: Bugfix update.</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>3.2</option></entry>
|
||||
<entry>06 Feb 2005</entry>
|
||||
<entry>BLUEBERRY release: Minor update.</entry>
|
||||
</row>
|
||||
</tbody>
|
||||
</tgroup>
|
||||
</table>
|
||||
|
|
|
|||
|
|
@ -36,3 +36,7 @@ echo # This 'echo' sometimes will not display.
|
|||
# The foreground loop preempts the background one.
|
||||
|
||||
exit 0
|
||||
|
||||
# Nasimuddin Ansari suggests adding sleep 1
|
||||
#+ after the echo -n "$i" in lines 6 and 14,
|
||||
#+ for some real fun.
|
||||
|
|
|
|||
|
|
@ -42,8 +42,13 @@ function get_xserver ()
|
|||
{
|
||||
case $TERM in
|
||||
xterm )
|
||||
XSERVER=$(who am i | awk '{print $NF}' | tr -d ')''(' )
|
||||
XSERVER=${XSERVER%%:*}
|
||||
XSERVER=$(who am i | awk '{print $NF}' | tr -d ')''(' )
|
||||
# Ane-Pieter Wieringa suggests the following alternative:
|
||||
# I_AM=$(who am i)
|
||||
# SERVER=${I_AM#*(}
|
||||
# SERVER=${SERVER%*)}
|
||||
|
||||
XSERVER=${XSERVER%%:*}
|
||||
;;
|
||||
aterm | rxvt)
|
||||
# find some code that works here.....
|
||||
|
|
|
|||
|
|
@ -22,6 +22,18 @@ echo "a (after --a) = $a"
|
|||
|
||||
echo
|
||||
|
||||
########################################################
|
||||
# Note that, as in C, pre- and post-decrement operators
|
||||
#+ have slightly different side-effects.
|
||||
|
||||
n=1; let --n && echo "True" || echo "False" # False
|
||||
n=1; let n-- && echo "True" || echo "False" # True
|
||||
|
||||
# Thanks, Jeroen Domburg.
|
||||
########################################################
|
||||
|
||||
echo
|
||||
|
||||
(( t = a<45?7:11 )) # C-style trinary operator.
|
||||
echo "If a < 45, then t = 7, else t = 11."
|
||||
echo "t = $t " # Yes!
|
||||
|
|
|
|||
|
|
@ -1,7 +1,7 @@
|
|||
#!/bin/bash
|
||||
# commentblock.sh
|
||||
|
||||
: << COMMENTBLOCK
|
||||
: <<COMMENTBLOCK
|
||||
echo "This line will not echo."
|
||||
This is a comment line missing the "#" prefix.
|
||||
This is another comment line missing the "#" prefix.
|
||||
|
|
@ -20,7 +20,7 @@ echo "Exit value of above \"COMMENTBLOCK\" is $?." # 0
|
|||
# This saves having to put a "#" at the beginning of each line,
|
||||
#+ then having to go back and delete each "#" later.
|
||||
|
||||
: << DEBUGXXX
|
||||
: <<DEBUGXXX
|
||||
for file in *
|
||||
do
|
||||
cat "$file"
|
||||
|
|
|
|||
|
|
@ -17,7 +17,7 @@ else
|
|||
fi
|
||||
|
||||
# Assumes all files in the target directory are MacPaint image files,
|
||||
# + with a ".mac" suffix.
|
||||
#+ with a ".mac" filename suffix.
|
||||
|
||||
for file in $directory/* # Filename globbing.
|
||||
do
|
||||
|
|
|
|||
|
|
@ -4,14 +4,14 @@
|
|||
# Script by Troy Engel.
|
||||
# Used with permission.
|
||||
|
||||
TCP_HOST=www.slashdot.org
|
||||
TCP_PORT=80 # Port 80 is http.
|
||||
TCP_HOST=www.dns-diy.com # A known spam-friendly ISP.
|
||||
TCP_PORT=80 # Port 80 is http.
|
||||
|
||||
# Try to connect. (Somewhat similar to a 'ping.')
|
||||
# Try to connect. (Somewhat similar to a 'ping' . . .)
|
||||
echo "HEAD / HTTP/1.0" >/dev/tcp/${TCP_HOST}/${TCP_PORT}
|
||||
MYEXIT=$?
|
||||
|
||||
: << EXPLANATION
|
||||
: <<EXPLANATION
|
||||
If bash was compiled with --enable-net-redirections, it has the capability of
|
||||
using a special character device for both TCP and UDP redirections. These
|
||||
redirections are used identically as STDIN/STDOUT/STDERR. The device entries
|
||||
|
|
|
|||
|
|
@ -33,7 +33,7 @@ declare -a \
|
|||
|
||||
|
||||
# Here document used as a comment block.
|
||||
: << LSfieldsDoc
|
||||
: <<LSfieldsDoc
|
||||
# # # # # List Filesystem Directory Information # # # # #
|
||||
#
|
||||
# ListDirectory "FileGlob" "Field-Array-Name"
|
||||
|
|
@ -163,7 +163,7 @@ IsNumber()
|
|||
# IndexList -if -of Field-Array-Filename Index-Array-Filename
|
||||
# # # # #
|
||||
|
||||
: << IndexListDoc
|
||||
: <<IndexListDoc
|
||||
Walk an array of directory fields produced by ListDirectory
|
||||
|
||||
Having suppressed the line breaks in an otherwise line oriented
|
||||
|
|
|
|||
|
|
@ -1,5 +1,9 @@
|
|||
#!/bin/bash
|
||||
|
||||
# Tip:
|
||||
# If you're unsure of how a certain condition would evaluate,
|
||||
#+ test it in an if-test.
|
||||
|
||||
echo
|
||||
|
||||
echo "Testing \"0\""
|
||||
|
|
@ -109,6 +113,7 @@ else
|
|||
fi # "$false" is false.
|
||||
# Now, we get the expected result.
|
||||
|
||||
# What would happen if we tested the uninitialized variable "$true"?
|
||||
|
||||
echo
|
||||
|
||||
|
|
|
|||
|
|
@ -1,4 +1,5 @@
|
|||
#!/bin/bash
|
||||
# ex18.sh
|
||||
|
||||
# Does a 'whois domain-name' lookup on any of 3 alternate servers:
|
||||
# ripe.net, cw.net, radb.net
|
||||
|
|
@ -10,15 +11,17 @@
|
|||
# ln -s /usr/local/bin/wh /usr/local/bin/wh-cw
|
||||
# ln -s /usr/local/bin/wh /usr/local/bin/wh-radb
|
||||
|
||||
E_NOARGS=65
|
||||
|
||||
|
||||
if [ -z "$1" ]
|
||||
then
|
||||
echo "Usage: `basename $0` [domain-name]"
|
||||
exit 65
|
||||
exit $E_NOARGS
|
||||
fi
|
||||
|
||||
case `basename $0` in
|
||||
# Checks script name and calls proper server
|
||||
# Check script name and call proper server.
|
||||
case `basename $0` in # Or: case ${0##*/} in
|
||||
"wh" ) whois $1@whois.ripe.net;;
|
||||
"wh-ripe") whois $1@whois.ripe.net;;
|
||||
"wh-radb") whois $1@whois.radb.net;;
|
||||
|
|
|
|||
|
|
@ -4,10 +4,12 @@
|
|||
# No argument checking.
|
||||
#
|
||||
# You might wish to add something like:
|
||||
#
|
||||
# E_NOARGS=65
|
||||
# if [ -z "$1" ]
|
||||
# then
|
||||
# echo "Usage: `basename $0` target-file"
|
||||
# exit 65
|
||||
# exit $E_NOARGS
|
||||
# fi
|
||||
|
||||
|
||||
|
|
@ -25,4 +27,7 @@ sed -e /^$/d "$1"
|
|||
# Quoting the command-line arg permits
|
||||
#+ whitespace and special characters in the filename.
|
||||
|
||||
# Note that this script doesn't actually change the target file.
|
||||
# If you need to do that, redirect its output.
|
||||
|
||||
exit 0
|
||||
|
|
|
|||
|
|
@ -22,7 +22,7 @@ printf "%s %s \n" $Message1 $Message2
|
|||
echo
|
||||
|
||||
# ==========================================#
|
||||
# Simulation of C function, 'sprintf'.
|
||||
# Simulation of C function, sprintf().
|
||||
# Loading a variable with a formatted string.
|
||||
|
||||
echo
|
||||
|
|
@ -33,7 +33,7 @@ echo "Pi to 12 decimal places = $Pi12"
|
|||
Msg=`printf "%s %s \n" $Message1 $Message2`
|
||||
echo $Msg; echo $Msg
|
||||
|
||||
# As it happens, the 'sprintf' function can now be accessed
|
||||
# as a loadable module to Bash, but this is not portable.
|
||||
# As it happens, the 'sprintf' function can now be accessed
|
||||
#+ as a loadable module to Bash, but this is not portable.
|
||||
|
||||
exit 0
|
||||
|
|
|
|||
|
|
@ -2,6 +2,11 @@
|
|||
|
||||
# Copying a directory tree using 'cpio.'
|
||||
|
||||
# Advantages of using 'cpio':
|
||||
# Speed of copying. It's faster than 'tar' with pipes.
|
||||
# Well suited for copying special files (named pipes, etc.)
|
||||
#+ that 'cp' may choke on.
|
||||
|
||||
ARGS=2
|
||||
E_BADARGS=65
|
||||
|
||||
|
|
@ -18,7 +23,11 @@ find "$source" -depth | cpio -admvp "$destination"
|
|||
# ^^^^^ ^^^^^
|
||||
# Read the 'find' and 'cpio' man page to decipher these options.
|
||||
|
||||
# It may be useful to check the exit status ($?) here
|
||||
#+ to see if everything worked all right.
|
||||
|
||||
# Exercise:
|
||||
# --------
|
||||
|
||||
# Add code to check the exit status ($?) of the 'find | cpio' pipe
|
||||
#+ and output appropriate error messages if anything went wrong.
|
||||
|
||||
exit 0
|
||||
|
|
|
|||
|
|
@ -3,39 +3,40 @@
|
|||
# --> Comments added by the author of this document marked by "# -->".
|
||||
|
||||
# --> This is part of the 'rc' script package
|
||||
# --> by Miquel van Smoorenburg, <miquels@drinkel.nl.mugnet.org>
|
||||
# --> by Miquel van Smoorenburg, <miquels@drinkel.nl.mugnet.org>.
|
||||
|
||||
# --> This particular script seems to be Red Hat specific
|
||||
# --> This particular script seems to be Red Hat / FC specific
|
||||
# --> (may not be present in other distributions).
|
||||
|
||||
# Bring down all unneeded services that are still running (there shouldn't
|
||||
# be any, so this is just a sanity check)
|
||||
# Bring down all unneeded services that are still running
|
||||
#+ (there shouldn't be any, so this is just a sanity check)
|
||||
|
||||
for i in /var/lock/subsys/*; do
|
||||
# --> Standard for/in loop, but since "do" is on same line,
|
||||
# --> it is necessary to add ";".
|
||||
# Check if the script is there.
|
||||
[ ! -f $i ] && continue
|
||||
# --> This is a clever use of an "and list", equivalent to:
|
||||
# --> if [ ! -f "$i" ]; then continue
|
||||
# Check if the script is there.
|
||||
[ ! -f $i ] && continue
|
||||
# --> This is a clever use of an "and list", equivalent to:
|
||||
# --> if [ ! -f "$i" ]; then continue
|
||||
|
||||
# Get the subsystem name.
|
||||
subsys=${i#/var/lock/subsys/}
|
||||
# --> Match variable name, which, in this case, is the file name.
|
||||
# --> This is the exact equivalent of subsys=`basename $i`.
|
||||
# Get the subsystem name.
|
||||
subsys=${i#/var/lock/subsys/}
|
||||
# --> Match variable name, which, in this case, is the file name.
|
||||
# --> This is the exact equivalent of subsys=`basename $i`.
|
||||
|
||||
# --> It gets it from the lock file name (if there is a lock file,
|
||||
# -->+ that's proof the process has been running).
|
||||
# --> See the "lockfile" entry, above.
|
||||
# --> It gets it from the lock file name
|
||||
# -->+ (if there is a lock file,
|
||||
# -->+ that's proof the process has been running).
|
||||
# --> See the "lockfile" entry, above.
|
||||
|
||||
|
||||
# Bring the subsystem down.
|
||||
if [ -f /etc/rc.d/init.d/$subsys.init ]; then
|
||||
/etc/rc.d/init.d/$subsys.init stop
|
||||
else
|
||||
/etc/rc.d/init.d/$subsys stop
|
||||
# Bring the subsystem down.
|
||||
if [ -f /etc/rc.d/init.d/$subsys.init ]; then
|
||||
/etc/rc.d/init.d/$subsys.init stop
|
||||
else
|
||||
/etc/rc.d/init.d/$subsys stop
|
||||
# --> Suspend running jobs and daemons.
|
||||
# --> Note that "stop" is a positional parameter,
|
||||
# -->+ not a shell builtin.
|
||||
fi
|
||||
fi
|
||||
done
|
||||
|
|
|
|||
|
|
@ -1,11 +1,11 @@
|
|||
#!/bin/bash
|
||||
# sieve.sh
|
||||
# sieve.sh (ex68.sh)
|
||||
|
||||
# Sieve of Eratosthenes
|
||||
# Ancient algorithm for finding prime numbers.
|
||||
|
||||
# This runs a couple of orders of magnitude
|
||||
# slower than the equivalent C program.
|
||||
# This runs a couple of orders of magnitude slower
|
||||
#+ than the equivalent program written in C.
|
||||
|
||||
LOWER_LIMIT=1 # Starting with 1.
|
||||
UPPER_LIMIT=1000 # Up to 1000.
|
||||
|
|
@ -33,8 +33,8 @@ do
|
|||
Primes[i]=$PRIME
|
||||
let "i += 1"
|
||||
done
|
||||
# Assume all array members guilty (prime)
|
||||
# until proven innocent.
|
||||
# Assume all array members guilty (prime)
|
||||
#+ until proven innocent.
|
||||
}
|
||||
|
||||
print_primes ()
|
||||
|
|
@ -89,11 +89,14 @@ done
|
|||
}
|
||||
|
||||
|
||||
# ==============================================
|
||||
# main ()
|
||||
# Invoke the functions sequentially.
|
||||
initialize
|
||||
sift
|
||||
print_primes
|
||||
# This is what they call structured programming.
|
||||
# ==============================================
|
||||
|
||||
echo
|
||||
|
||||
|
|
@ -104,8 +107,8 @@ exit 0
|
|||
# ----------------------------------------------- #
|
||||
# Code below line will not execute.
|
||||
|
||||
# This improved version of the Sieve, by Stephane Chazelas,
|
||||
# executes somewhat faster.
|
||||
# This improved version of the Sieve, by Stephane Chazelas,
|
||||
#+ executes somewhat faster.
|
||||
|
||||
# Must invoke with command-line argument (limit of primes).
|
||||
|
||||
|
|
|
|||
|
|
@ -1,11 +1,11 @@
|
|||
#!/bin/bash
|
||||
# fileinfo.sh
|
||||
|
||||
FILES="/usr/sbin/privatepw
|
||||
FILES="/usr/sbin/accept
|
||||
/usr/sbin/pwck
|
||||
/usr/sbin/go500gw
|
||||
/usr/sbin/chroot
|
||||
/usr/bin/fakefile
|
||||
/sbin/mkreiserfs
|
||||
/sbin/badblocks
|
||||
/sbin/ypbind" # List of files you are curious about.
|
||||
# Threw in a dummy file, /usr/bin/fakefile.
|
||||
|
||||
|
|
@ -22,6 +22,8 @@ do
|
|||
|
||||
ls -l $file | awk '{ print $9 " file size: " $5 }' # Print 2 fields.
|
||||
whatis `basename $file` # File info.
|
||||
# Note that the whatis database needs to have been set up for this to work.
|
||||
# To do this, as root run /usr/bin/makewhatis.
|
||||
echo
|
||||
done
|
||||
|
||||
|
|
|
|||
|
|
@ -23,7 +23,9 @@ fi
|
|||
|
||||
inum=`ls -i | grep "$1" | awk '{print $1}'`
|
||||
# inum = inode (index node) number of file
|
||||
# ----------------------------------------------------------------------
|
||||
# Every file has an inode, a record that hold its physical address info.
|
||||
# ----------------------------------------------------------------------
|
||||
|
||||
echo; echo -n "Are you absolutely sure you want to delete \"$1\" (y/n)? "
|
||||
# The '-v' option to 'rm' also asks this.
|
||||
|
|
|
|||
|
|
@ -58,7 +58,7 @@ trap - SIGRTMIN
|
|||
|
||||
exit $?
|
||||
|
||||
: << SCRIPT_AUTHOR_COMMENTS
|
||||
: <<SCRIPT_AUTHOR_COMMENTS
|
||||
I had the need to run a program, with specified options, on a number of
|
||||
different files, using a SMP machine. So I thought [I'd] keep running
|
||||
a specified number of processes and start a new one each time . . . one
|
||||
|
|
|
|||
|
|
@ -79,4 +79,4 @@ done
|
|||
echo "On-line"
|
||||
|
||||
# Exercise: Discuss the relative strengths and weaknesses
|
||||
#! of each of these various approaches.
|
||||
# of each of these various approaches.
|
||||
|
|
|
|||
|
|
@ -6,18 +6,38 @@
|
|||
#+ even if the variable is null.
|
||||
|
||||
username0=
|
||||
# username0 has been declared, but is set to null.
|
||||
echo "username0 has been declared, but is set to null."
|
||||
echo "username0 = ${username0-`whoami`}"
|
||||
# Will not echo.
|
||||
|
||||
echo
|
||||
|
||||
echo username1 has not been declared.
|
||||
echo "username1 = ${username1-`whoami`}"
|
||||
# username1 has not been declared.
|
||||
# Will echo.
|
||||
|
||||
username2=
|
||||
# username2 has been declared, but is set to null.
|
||||
echo "username2 has been declared, but is set to null."
|
||||
echo "username2 = ${username2:-`whoami`}"
|
||||
# ^
|
||||
# Will echo because of :- rather than just - in condition test.
|
||||
# Compare to first instance, above.
|
||||
|
||||
|
||||
# =============================================================
|
||||
|
||||
# Reiterating:
|
||||
|
||||
variable=
|
||||
# variable has been declared, but is set to null.
|
||||
|
||||
echo "${variable-0}" # (no output)
|
||||
echo "${variable:-1}" # 1
|
||||
# ^
|
||||
|
||||
unset variable
|
||||
|
||||
echo "${variable-2}" # 2
|
||||
echo "${variable:-3}" # 3
|
||||
|
||||
exit 0
|
||||
|
|
|
|||
|
|
@ -4,7 +4,7 @@
|
|||
RANDOM=$$ # Reseed the random number generator using script process ID.
|
||||
|
||||
PIPS=6 # A die has 6 pips.
|
||||
MAXTHROWS=600 # Increase this, if you have nothing better to do with your time.
|
||||
MAXTHROWS=600 # Increase this if you have nothing better to do with your time.
|
||||
throw=0 # Throw count.
|
||||
|
||||
ones=0 # Must initialize counts to zero,
|
||||
|
|
@ -50,6 +50,8 @@ done
|
|||
|
||||
print_result
|
||||
|
||||
exit 0
|
||||
|
||||
# The scores should distribute fairly evenly, assuming RANDOM is fairly random.
|
||||
# With $MAXTHROWS at 600, all should cluster around 100, plus-or-minus 20 or so.
|
||||
#
|
||||
|
|
@ -64,5 +66,3 @@ print_result
|
|||
# ---------------
|
||||
# Rewrite this script to flip a coin 1000 times.
|
||||
# Choices are "HEADS" and "TAILS".
|
||||
|
||||
exit 0
|
||||
|
|
|
|||
|
|
@ -11,7 +11,7 @@ then
|
|||
sed -e '/DOCUMENTATIONXX$/d'; exit $DOC_REQUEST; fi
|
||||
|
||||
|
||||
: << DOCUMENTATIONXX
|
||||
: <<DOCUMENTATIONXX
|
||||
List the statistics of a specified directory in tabular format.
|
||||
---------------------------------------------------------------
|
||||
The command line parameter gives the directory to be listed.
|
||||
|
|
|
|||
|
|
@ -13,18 +13,18 @@ let "pass_count += 1"
|
|||
#+ can be incremented the first time around.
|
||||
# This works with Bash and pdksh, but
|
||||
#+ it relies on non-portable (and possibly dangerous) behavior.
|
||||
# Better would be to set $pass_count to 0 if non-initialized.
|
||||
# Better would be to initialize $pass_count to 0 before incrementing.
|
||||
|
||||
while [ "$pass_count" -le $MAXPASSCNT ]
|
||||
do
|
||||
. $0 # Script "sources" itself, rather than calling itself.
|
||||
# ./$0 (which would be true recursion) doesn't work here.
|
||||
# ./$0 (which would be true recursion) doesn't work here. Why?
|
||||
done
|
||||
|
||||
# What occurs here is not actually recursion,
|
||||
#+ since the script effectively "expands" itself
|
||||
#+ (generates a new section of code)
|
||||
#+ with each pass throught the 'while' loop',
|
||||
#+ since the script effectively "expands" itself, i.e.,
|
||||
#+ generates a new section of code
|
||||
#+ with each pass through the 'while' loop',
|
||||
# with each 'source' in line 20.
|
||||
#
|
||||
# Of course, the script interprets each newly 'sourced' "#!" line
|
||||
|
|
@ -37,4 +37,4 @@ exit 0 # The net effect is counting from 1 to 100.
|
|||
|
||||
# Exercise:
|
||||
# --------
|
||||
# Write a script that uses this trick to do something useful.
|
||||
# Write a script that uses this trick to actually do something useful.
|
||||
|
|
|
|||
|
|
@ -4,7 +4,7 @@
|
|||
echo
|
||||
|
||||
echo "Subshell level OUTSIDE subshell = $BASH_SUBSHELL"
|
||||
# Bash, version 3, adds the new $BASH_SUBSELL variable.
|
||||
# Bash, version 3, adds the new $BASH_SUBSHELL variable.
|
||||
echo
|
||||
|
||||
outer_variable=Outer
|
||||
|
|
|
|||
|
|
@ -2,6 +2,9 @@
|
|||
# ==> usb.sh
|
||||
# ==> Script for mounting and installing pen/keychain USB storage devices.
|
||||
# ==> Runs as root at system startup (see below).
|
||||
# ==>
|
||||
# ==> Newer Linux distros (2004 or later) autodetect
|
||||
# ==> and install USB pen drives, and therefore don't need this script.
|
||||
|
||||
# This code is free software covered by GNU GPL license version 2 or above.
|
||||
# Please refer to http://www.gnu.org/ for the full license text.
|
||||
|
|
|
|||
Loading…
Reference in New Issue