mirror of https://github.com/tLDP/LDP
updated
This commit is contained in:
gferg
parent
a748bd3591
commit
95201486ee
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@ -6,6 +6,71 @@
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http://personal.riverusers.com/~thegrendel/Change.log
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------------------------------------------------------------------------
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Version 3.5
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Boxberry release, 06/05/05
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1) In "Indirect References to Variables" section of "Variables Revisited" chapter:
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Added "ugly kludge" sidebar.
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2) In "Variable Assignment" section of "Introduction to Variables and
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Parameters" chapter:
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After "ex16.sh" example, noted that $(...) construct is a form of
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command substitution.
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3) In "Special Variable Types" section of "Introduction to Variables and
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Parameters" chapter:
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In note about remedies for missing command-line parameters,
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added discussion about using parameter substitution,
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rather than adding extra characters to variable names.
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(Thank you, Fabian Kreutz.)
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4) In "Command Substitution" chapter:
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At note at end of chapter, added mention that nesting is possible
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with $(...) construct, and added "agram2.sh" example script.
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5) In "Internal Commands and Builtins" chapter:
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At "exec" entry, added footnote and streamlined text.
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6) In "File and Archiving Commands" section of "External Commands" Chapter:
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At "more/less" entry, added "testing command sequence" usage example.
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At "mktemp" entry, added usage example and elaborated existing example.
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7) In "Communications Commands" section of "External Commands" chapter:
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At "dig" entry, added "spam-lookup.sh" example.
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8) In "Text Processing" section of "External Commands" Chapter:
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At "tail" entry, added usage example of combining "head" and "tail"
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to extract a specific line or lines from a text file.
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9) In "System and Administrative Commands" chapter:
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At "umask" entry, added "rot13a.sh" example script.
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10) In "Complex Functions and Function Complexities" section of "Functions"
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chapter:
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Added in-line example ("days in month") of capturing function "echo"
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as "return value."
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11) In the "Shell Wrappers" section of "Miscellany" chapter:
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Added "pr-asc.sh" example script.
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12) Changed "Files" chapter into an appendix.
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13) In the "Sed and Awk Micro-primer" appendix:
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More examples of the awk "print" command.
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14) In "Contributed Scripts" appendix:
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Added "whx.sh" script.
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(Thank you, Walter Dnes.)
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15) Miscellaneous fixups and stylistic changes in the text and various
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scripts.
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Fixed up three misspellings of "permissible"!
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Updated morethan.org site address.
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Version 3.4
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Teaberry release, 05/08/05
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@ -259,7 +324,8 @@ Blueberry release, 02/06/05
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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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4) In "Complex Functions and Function Complexities" section of "Functions"
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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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@ -22,21 +22,21 @@ require no fixups to execute as expected.
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Scripts needing to be altered:
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-----------------------------
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Du.sh
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Du.sh (line 19)
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encryptedpw.sh (lines 27 and 35)
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ex57.sh
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ex70.sh
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ex71.sh
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ex71a.sh
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ex71b.sh
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logevents.sh
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m4.sh
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pb.sh
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pw.sh
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read-r.sh
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rnd.sh
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rot13.sh
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here-function.sh
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ex57.sh (comment in line 8)
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ex70.sh (line 3)
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ex71.sh (line 7)
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ex71a.sh (line 8)
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ex71b.sh (line 22)
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logevents.sh (lines 29, 36-39, 44, 53, 55, 60, 64)
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m4.sh (line 8)
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pw.sh (comment in line 4)
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read-r.sh (lines 5, 6, 19, 26)
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rnd.sh (comments in lines 38, 55, 64)
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rot13.sh (comment, line 6)
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rot13a.sh (comment, line 5)
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here-function.sh (line 16)
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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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@ -59,3 +59,5 @@ Hash.lib, (comments in lines lines 103 and 116: & --> &)
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(comment in line 3: < --> <, > --> >)
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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 230)
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@ -140,6 +140,7 @@ Uncomment line below to generate index.
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<!ENTITY lookup SYSTEM "lookup.sh">
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<!ENTITY arglist SYSTEM "arglist.sh">
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<!ENTITY rot13 SYSTEM "rot13.sh">
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<!ENTITY rot13a SYSTEM "rot13a.sh">
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<!ENTITY rot14 SYSTEM "rot14.sh">
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<!ENTITY filecomp SYSTEM "file-comparison.sh">
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<!ENTITY adddrv SYSTEM "add-drive.sh">
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@ -260,6 +261,7 @@ Uncomment line below to generate index.
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<!ENTITY factr SYSTEM "factr.sh">
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<!ENTITY cannon SYSTEM "cannon.sh">
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<!ENTITY agram SYSTEM "agram.sh">
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<!ENTITY agram2 SYSTEM "agram2.sh">
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<!ENTITY poem SYSTEM "poem.sh">
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<!ENTITY soundex SYSTEM "soundex.sh">
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<!ENTITY tempfilename SYSTEM "tempfile-name.sh">
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@ -322,6 +324,9 @@ Uncomment line below to generate index.
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<!ENTITY hashlib SYSTEM "Hash.lib">
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<!ENTITY hashexample SYSTEM "hash-example.sh">
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<!ENTITY getoptsimple SYSTEM "getopt-simple.sh">
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<!ENTITY prasc SYSTEM "pr-asc.sh">
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<!ENTITY whx SYSTEM "whx.sh">
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<!ENTITY spamlookup SYSTEM "spam-lookup.sh">
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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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@ -342,19 +347,12 @@ Uncomment line below to generate index.
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</affiliation>
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</author>
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<releaseinfo>3.4</releaseinfo>
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<pubdate>08 May 2005</pubdate>
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<releaseinfo>3.5</releaseinfo>
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<pubdate>05 June 2005</pubdate>
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<revhistory>
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<revision>
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<revnumber>3.1</revnumber>
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<date>14 Nov 2004</date>
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<authorinitials>mc</authorinitials>
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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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@ -376,6 +374,13 @@ Uncomment line below to generate index.
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<revremark>'TEABERRY' release: Important Update.</revremark>
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</revision>
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<revision>
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<revnumber>3.5</revnumber>
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<date>04 June 2005</date>
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<authorinitials>mc</authorinitials>
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<revremark>'BOXBERRY' release: Important Update.</revremark>
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</revision>
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</revhistory>
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@ -396,7 +401,7 @@ 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-3.4.tar.bz2">
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url="http://personal.riverusers.com/~thegrendel/abs-guide-3.5.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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@ -3047,7 +3052,9 @@ echo "$uninitialized" # 5
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<para>Variable assignment using the <firstterm>$(...)</firstterm>
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mechanism (a newer method than <link
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linkend="backquotesref">backquotes</link>)</para>
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linkend="backquotesref">backquotes</link>). This is
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actually a form of <link linkend="commandsubref">command
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substitution</link>.</para>
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<para><programlisting># From /etc/rc.d/rc.local
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R=$(cat /etc/redhat-release)
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@ -3247,7 +3254,15 @@ variable1=${variable1_/_/}
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if [ -z $1 ]
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then
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exit $E_MISSING_POS_PARAM
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fi
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fi
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# However, as Fabian Kreutz points out,
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#+ the above method may have unexpected side-effects.
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# A better method is parameter substitution:
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# ${1:-$DefaultVal}
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# See the "Parameter Substition" section
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#+ in the "Variables Revisited" chapter.
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</programlisting>
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<para>---</para>
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@ -4832,8 +4847,9 @@ home=/home/bozo
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<programlisting>if [ "$exp1" -a "$exp2" ]</programlisting>
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</para>
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<para>Refer to <xref linkend="andor"> and <xref linkend="twodim">
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to see compound comparison operators in action.</para>
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<para>Refer to <xref linkend="andor">, <xref linkend="twodim">,
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and <xref linkend="whx"> to see compound comparison operators
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in action.</para>
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</sect1> <!-- Comparison operators (binary) -->
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@ -8238,6 +8254,13 @@ echo $? # 1
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(see <xref linkend="ex78">) makes indirect referencing more
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intuitive.</para></caution>
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||||
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<sidebar>
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<para>Bash does not support pointer arithmetic, and this severely
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limits the usefulness of indirect referencing. In fact, indirect
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referencing in a scripting language is an ugly kludge.</para>
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||||
</sidebar>
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||||
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||||
</sect1> <!-- Indirect References to Variables -->
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@ -8416,16 +8439,17 @@ rnumber=$(((RANDOM%30/3+1)*3))
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<title>Loops and Branches</title>
|
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<para>Operations on code blocks are the key to structured, organized
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<para>Operations on code blocks are the key to structured and organized
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shell scripts. Looping and branching constructs provide the tools for
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accomplishing this.</para>
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<sect1 id="loops1">
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<title>Loops</title>
|
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<para>A <firstterm>loop</firstterm> is a block of code that iterates
|
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(repeats) a list of commands as long as the <firstterm>loop
|
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control condition</firstterm> is true.</para>
|
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<para>A <firstterm>loop</firstterm> is a block of code that
|
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<firstterm>iterates</firstterm> (repeats) a list of commands
|
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as long as the <firstterm>loop control condition</firstterm>
|
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is true.</para>
|
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|
||||
|
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<variablelist id="forloopref">
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|
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@ -8469,11 +8493,11 @@ rnumber=$(((RANDOM%30/3+1)*3))
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<replaceable>list</replaceable>.</para></note>
|
||||
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||||
<para><programlisting>for arg in "$var1" "$var2" "$var3" ... "$varN"
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# In pass 1 of the loop, $arg = $var1
|
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# In pass 2 of the loop, $arg = $var2
|
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# In pass 3 of the loop, $arg = $var3
|
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# In pass 1 of the loop, arg = $var1
|
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# In pass 2 of the loop, arg = $var2
|
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# In pass 3 of the loop, arg = $var3
|
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# ...
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# In pass N of the loop, $arg = $varN
|
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# In pass N of the loop, arg = $varN
|
||||
|
||||
# Arguments in [list] quoted to prevent possible word splitting.</programlisting></para>
|
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|
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|
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@ -8501,11 +8525,11 @@ rnumber=$(((RANDOM%30/3+1)*3))
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|
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<note><para>Each <userinput>[list]</userinput> element
|
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may contain multiple parameters. This is useful when
|
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processing parameters in groups. In such cases, use the
|
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<command>set</command> command (see <xref linkend="ex34">)
|
||||
to force parsing of each <userinput>[list]</userinput>
|
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element and assignment of each component to the positional
|
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parameters.</para></note>
|
||||
processing parameters in groups. In such cases,
|
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use the <link linkend="setref">set</link> command
|
||||
(see <xref linkend="ex34">) to force parsing of each
|
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<userinput>[list]</userinput> element and assignment of
|
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each component to the positional parameters.</para></note>
|
||||
|
||||
<example id="ex22a">
|
||||
<title><command>for</command> loop with two parameters in each
|
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|
|
@ -10193,16 +10217,19 @@ shift $(($OPTIND - 1))
|
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</indexterm>
|
||||
<listitem>
|
||||
|
||||
<para>This shell builtin replaces the current process with
|
||||
<para>
|
||||
This shell builtin replaces the current process with
|
||||
a specified command. Normally, when the shell encounters
|
||||
a command, it <link linkend="forkref">forks off</link> a
|
||||
child process to actually execute the command. Using the
|
||||
<command>exec</command> builtin, the shell does not fork,
|
||||
and the command exec'ed replaces the shell. When used in
|
||||
a script, therefore, it forces an exit from the script when
|
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the <command>exec</command>'ed command terminates. For this
|
||||
reason, if an <command>exec</command> appears in a script,
|
||||
it would probably be the final command.</para>
|
||||
the <command>exec</command>'ed command terminates.
|
||||
<footnote><para>Unless the <command>exec</command> is used
|
||||
to <link linkend="usingexecref">reassign file
|
||||
descriptors</link>.</para></footnote>
|
||||
</para>
|
||||
|
||||
<example id="ex54">
|
||||
<title>Effects of <command>exec</command></title>
|
||||
|
|
@ -10214,11 +10241,11 @@ shift $(($OPTIND - 1))
|
|||
<programlisting>&selfexec;</programlisting>
|
||||
</example>
|
||||
|
||||
<para>An <command>exec</command> also serves to reassign <link
|
||||
linkend="fdref">file descriptors</link>. <userinput>exec
|
||||
<para>An <command>exec</command> also serves to <link
|
||||
linkend="usingexecref">reassign
|
||||
file descriptors</link>. For example, <userinput>exec
|
||||
<zzz-file</userinput> replaces <filename>stdin</filename>
|
||||
with the file <filename>zzz-file</filename> (see <xref
|
||||
linkend="redir1">).</para>
|
||||
with the file <filename>zzz-file</filename>.</para>
|
||||
|
||||
<note><para>The <option>-exec</option> option to
|
||||
<link linkend="findref">find</link> is
|
||||
|
|
@ -11392,12 +11419,12 @@ chmod u+s filename
|
|||
<listitem>
|
||||
<para>-exec <replaceable>COMMAND</replaceable> \;</para>
|
||||
<para>Carries out <replaceable>COMMAND</replaceable> on
|
||||
each file that <command>find</command> matches.
|
||||
The command sequence terminates with <token>\;</token>
|
||||
(the <quote>;</quote> is escaped to make certain
|
||||
the shell passes it to <command>find</command>
|
||||
literally).</para>
|
||||
|
||||
each file that <command>find</command> matches. The
|
||||
command sequence terminates with <token>;</token> (the
|
||||
<quote>;</quote> is <link linkend="escp">escaped</link> to
|
||||
make certain the shell passes it to <command>find</command>
|
||||
literally, without interpreting it as a special character).</para>
|
||||
|
||||
|
||||
<para>
|
||||
<screen><prompt>bash$ </prompt><userinput>find ~/ -name '*.txt'</userinput>
|
||||
|
|
@ -12380,6 +12407,21 @@ done
|
|||
<programlisting>&ex12;</programlisting>
|
||||
</example>
|
||||
|
||||
<tip>
|
||||
<para>To list a specific line of a text file,
|
||||
<link linkend="piperef">pipe</link> the output of
|
||||
<command>head</command> to <command>tail -1</command>.
|
||||
For example <userinput>head -8 database.txt | tail
|
||||
-1</userinput> lists the 8th line of the file
|
||||
<filename>database.txt</filename>.</para>
|
||||
<para>To set a variable to a given block of a text file:
|
||||
<programlisting>var=$(head -$m $filename | tail -$n)
|
||||
|
||||
# filename = name of file
|
||||
# m = from beginning of file, number of lines to end of block
|
||||
# n = number of lines to set variable to (trim from end of block)</programlisting></para>
|
||||
</tip>
|
||||
|
||||
<para>See also <xref linkend="ex41">, <xref linkend="ex52"> and
|
||||
<xref linkend="online">.</para>
|
||||
|
||||
|
|
@ -14501,15 +14543,39 @@ gzip -cd patchXX.gz | patch -p0
|
|||
<secondary>filename</secondary>
|
||||
</indexterm>
|
||||
<listitem>
|
||||
<para>Create a temporary file with a <quote>unique</quote>
|
||||
filename.</para>
|
||||
<para>Create a <firstterm>temporary file</firstterm>
|
||||
|
||||
<footnote><para>Creates a temporary
|
||||
<emphasis>directory</emphasis> when invoked with the
|
||||
<option>-d</option> option.</para></footnote>
|
||||
|
||||
with a <quote>unique</quote> filename. When invoked
|
||||
from the command line without additional arguments,
|
||||
it creates a zero-length file in the <filename
|
||||
class="directory">/tmp</filename> directory.</para>
|
||||
|
||||
|
||||
<para>
|
||||
<screen><prompt>bash$ </prompt><userinput>mktemp</userinput>
|
||||
<computeroutput>/tmp/tmp.zzsvql3154</computeroutput>
|
||||
</screen>
|
||||
</para>
|
||||
|
||||
<para><programlisting>PREFIX=filename
|
||||
tempfile=`mktemp $PREFIX.XXXXXX`
|
||||
# ^^^^^^ Need at least 6 placeholders
|
||||
#+ in the filename template.
|
||||
# If no filename template supplied,
|
||||
#+ "tmp.XXXXXXXXXX" is the default.
|
||||
|
||||
echo "tempfile name = $tempfile"
|
||||
# tempfile name = filename.QA2ZpY
|
||||
# or something similar...</programlisting></para>
|
||||
# or something similar...
|
||||
|
||||
# Creates a file of that name in the current working directory
|
||||
#+ with 600 file permissions.
|
||||
# A "umask 177" is therefore unnecessary,
|
||||
# but it's good programming practice anyhow.</programlisting></para>
|
||||
</listitem>
|
||||
</varlistentry>
|
||||
|
||||
|
|
@ -14606,9 +14672,24 @@ echo "tempfile name = $tempfile"
|
|||
<secondary>less</secondary>
|
||||
</indexterm>
|
||||
<listitem>
|
||||
|
||||
<para>Pagers that display a text file or stream to
|
||||
<filename>stdout</filename>, one screenful at a time.
|
||||
These may be used to filter the output of a script.</para>
|
||||
These may be used to filter the output of
|
||||
<filename>stdout</filename> . . . or of a script.</para>
|
||||
|
||||
<para>
|
||||
An interesting application of <command>more</command>
|
||||
is to <quote>test drive</quote> a command sequence,
|
||||
to forestall potentially unpleasant consequences.
|
||||
<programlisting>ls /home/bozo | awk '{print "rm -rf " $1}' | more
|
||||
# ^^^^
|
||||
|
||||
# Testing the effect of the following (disastrous) command line:
|
||||
# ls /home/bozo | awk '{print "rm -rf " $1}' | sh
|
||||
# Hand off to the shell to execute . . . ^^</programlisting>
|
||||
</para>
|
||||
|
||||
</listitem>
|
||||
</varlistentry>
|
||||
|
||||
|
|
@ -14752,8 +14833,13 @@ echo "tempfile name = $tempfile"
|
|||
</screen>
|
||||
</para>
|
||||
|
||||
<example id="spamlookup">
|
||||
<title>Finding out where to report a spammer</title>
|
||||
<programlisting>&spamlookup;</programlisting>
|
||||
</example>
|
||||
|
||||
<example id="isspammer">
|
||||
<title>Checking a spam domain</title>
|
||||
<title>Analyzing a spam domain</title>
|
||||
<programlisting>&isspammer;</programlisting>
|
||||
</example>
|
||||
|
||||
|
|
@ -14843,7 +14929,7 @@ echo "tempfile name = $tempfile"
|
|||
<para>Perform a DNS (Domain Name System) lookup.
|
||||
The <option>-h</option> option permits specifying which
|
||||
particular <emphasis>whois</emphasis> server to query. See
|
||||
<xref linkend="ex18">.</para>
|
||||
<xref linkend="ex18"> and <xref linkend="spamlookup">.</para>
|
||||
</listitem>
|
||||
</varlistentry>
|
||||
|
||||
|
|
@ -19119,18 +19205,20 @@ exit 0 # Will not exit here, because this script will never terminate.</pr
|
|||
</indexterm>
|
||||
<term><anchor id="umaskref"><command>umask</command></term>
|
||||
<listitem>
|
||||
<para>User file creation MASK. Limit the default file attributes
|
||||
for a particular user. All files created by that user take
|
||||
on the attributes specified by <command>umask</command>. The
|
||||
(octal) value passed to <command>umask</command> defines the
|
||||
file permissions <emphasis>disabled</emphasis>. For example,
|
||||
<command>umask 022</command> ensures that new files will
|
||||
have at most 755 permissions (777 NAND 022).
|
||||
<para>User file creation permissions
|
||||
<firstterm>mask</firstterm>. Limit the default file
|
||||
attributes for a particular user. All files created
|
||||
by that user take on the attributes specified by
|
||||
<command>umask</command>. The (octal) value passed to
|
||||
<command>umask</command> defines the file permissions
|
||||
<firstterm>disabled</firstterm>. For example, <command>umask
|
||||
022</command> ensures that new files will have at most
|
||||
755 permissions (777 NAND 022).
|
||||
|
||||
<footnote><para>NAND is the logical
|
||||
<firstterm>not-and</firstterm> operator. Its effect
|
||||
is somewhat similar to subtraction.</para></footnote>
|
||||
|
||||
<footnote><para>NAND is the logical <quote>not-and</quote>
|
||||
operator. Its effect is somewhat similar to
|
||||
subtraction.</para></footnote>
|
||||
|
||||
Of course, the user may later change the
|
||||
attributes of particular files with <link
|
||||
linkend="chmodref">chmod</link>. The usual practice
|
||||
|
|
@ -19139,6 +19227,12 @@ exit 0 # Will not exit here, because this script will never terminate.</pr
|
|||
<filename>~/.bash_profile</filename> (see <xref
|
||||
linkend="files">).</para>
|
||||
|
||||
<example id="rot13a">
|
||||
<title>Using <command>umask</command> to hide an output file
|
||||
from prying eyes</title>
|
||||
<programlisting>&rot13a;</programlisting>
|
||||
</example>
|
||||
|
||||
</listitem>
|
||||
</varlistentry>
|
||||
|
||||
|
|
@ -19746,6 +19840,19 @@ File_contents2=$(<$file2) # Bash permits this also.</programlisting></
|
|||
</screen>
|
||||
</para>
|
||||
|
||||
<para>Unlike backticks, the <command>$(...)</command> form of
|
||||
command substitution permits nesting.</para>
|
||||
|
||||
<para><programlisting>word_count=$( wc -w $(ls -l | awk '{print $9}') )</programlisting>
|
||||
</para>
|
||||
|
||||
<para>Or, for something a bit more elaborate . . .</para>
|
||||
|
||||
<example id="agram2">
|
||||
<title>Finding anagrams</title>
|
||||
<programlisting>&agram2;</programlisting>
|
||||
</example>
|
||||
|
||||
|
||||
</note>
|
||||
|
||||
|
|
@ -20099,6 +20206,8 @@ exec 3>&- # Now close it for the remainder of the s
|
|||
<sect1><title>Using <command>exec</command></title>
|
||||
|
||||
|
||||
<para><anchor id="usingexecref"></para>
|
||||
|
||||
<para>An <command>exec <filename</command> command redirects
|
||||
<filename>stdin</filename> to a file. From that point on, all
|
||||
<filename>stdin</filename> comes from that file, rather than
|
||||
|
|
@ -21898,7 +22007,7 @@ f2 ()
|
|||
|
||||
f1 # Function "f2" is not actually called until this point,
|
||||
#+ although it is referenced before its definition.
|
||||
# This is permissable.
|
||||
# This is permissible.
|
||||
|
||||
# Thanks, S.C.</programlisting>
|
||||
</para>
|
||||
|
|
@ -21929,7 +22038,7 @@ f2 # Now, it's all right to call "f2",
|
|||
|
||||
<para>Function declarations can appear in unlikely places, even where a
|
||||
command would otherwise go.
|
||||
<programlisting>ls -l | foo() { echo "foo"; } # Permissable, but useless.
|
||||
<programlisting>ls -l | foo() { echo "foo"; } # Permissible, but useless.
|
||||
|
||||
|
||||
|
||||
|
|
@ -22146,10 +22255,10 @@ echo "return value = $Return_Val" #25701</programlisting>
|
|||
</para>
|
||||
|
||||
|
||||
<para>An even more elegant method is to simply have the
|
||||
function <command>echo</command> its <quote>return
|
||||
value to <filename>stdout</filename>,</quote> and to
|
||||
then capture it by <link linkend="commandsubref">command
|
||||
<para>A more elegant method is to have the function
|
||||
<command>echo</command> its <quote>return
|
||||
value to <filename>stdout</filename>,</quote> and
|
||||
then capture it by <link linkend="commandsubref">command
|
||||
substitution</link>. See the <link linkend="rvt">discussion
|
||||
of this</link> in <xref linkend="assortedtips">.</para>
|
||||
|
||||
|
|
@ -22158,6 +22267,32 @@ echo "return value = $Return_Val" #25701</programlisting>
|
|||
<programlisting>&max2;</programlisting>
|
||||
</example>
|
||||
|
||||
<para>Here is another example of capturing a function
|
||||
<quote>return value.</quote> Understanding it requires some
|
||||
knowledge of <link linkend="awkref">awk</link>.
|
||||
|
||||
<programlisting>month_length () # Takes month number as an argument.
|
||||
{ # Returns number of days in month.
|
||||
monthD="31 28 31 30 31 30 31 31 30 31 30 31" # Declare as local?
|
||||
echo "$monthD" | awk '{ print $'"${1}"' }' # Tricky.
|
||||
# ^^^^^^^^^
|
||||
# Parameter passed to function ($1 -- month number), then to awk.
|
||||
# Awk sees this as "print $1 . . . print $12" (depending on month number)
|
||||
# Template for passing a parameter to embedded awk script:
|
||||
# $'"${script_parameter}"'
|
||||
|
||||
# Needs error checking for correct parameter range (1-12)
|
||||
#+ and for February in leap year.
|
||||
}
|
||||
|
||||
# ----------------------------------------------
|
||||
# Usage example:
|
||||
month=4 # April, for example (4th month).
|
||||
days_in=$(month_length $month)
|
||||
echo $days_in # 30
|
||||
# ----------------------------------------------</programlisting></para>
|
||||
|
||||
|
||||
<para>See also <xref linkend="daysbetween">.</para>
|
||||
|
||||
<para><userinput>Exercise:</userinput> Using what we have
|
||||
|
|
@ -22194,7 +22329,7 @@ echo "return value = $Return_Val" #25701</programlisting>
|
|||
<programlisting>&realname;</programlisting>
|
||||
</example>
|
||||
|
||||
<para>There is an alternative, and perhaps less confusing
|
||||
<para>There is an alternate, and perhaps less confusing
|
||||
method of redirecting a function's
|
||||
<filename>stdin</filename>. This involves redirecting the
|
||||
<filename>stdin</filename> to an embedded bracketed code
|
||||
|
|
@ -22870,7 +23005,7 @@ exit 0</programlisting></para>
|
|||
|
||||
<para>--</para>
|
||||
|
||||
<para>Bash supports only one-dimensional arrays, however a little
|
||||
<para>Bash supports only one-dimensional arrays, though a little
|
||||
trickery permits simulating multi-dimensional ones.</para>
|
||||
|
||||
<example id="twodim">
|
||||
|
|
@ -22879,96 +23014,25 @@ exit 0</programlisting></para>
|
|||
</example>
|
||||
|
||||
<para>A two-dimensional array is essentially equivalent to a
|
||||
one-dimensional one, but with additional addressing modes for
|
||||
referencing and manipulating the individual elements by
|
||||
<quote>row</quote> and <quote>column</quote> position.</para>
|
||||
one-dimensional one, but with additional addressing modes
|
||||
for referencing and manipulating the individual elements
|
||||
by <emphasis>row</emphasis> and <emphasis>column</emphasis>
|
||||
position.</para>
|
||||
|
||||
<para>For an even more elaborate example of simulating a
|
||||
two-dimensional array, see <xref linkend="lifeslow">.</para>
|
||||
|
||||
<para>--</para>
|
||||
|
||||
<para>For yet another interesting script using arrays, see:
|
||||
<itemizedlist>
|
||||
<listitem><para><xref linkend="agram2"></para></listitem>
|
||||
</itemizedlist>
|
||||
</para>
|
||||
|
||||
</chapter> <!-- Arrays -->
|
||||
|
||||
|
||||
|
||||
<chapter id="files">
|
||||
<title>Files</title>
|
||||
|
||||
<variablelist id="filesref">
|
||||
<title><anchor id="filesref1">startup files</title>
|
||||
|
||||
<varlistentry>
|
||||
<term></term>
|
||||
<listitem>
|
||||
<para>These files contain the aliases and <link
|
||||
linkend="envref">environmental variables</link>
|
||||
made available to Bash running as a user shell and to all
|
||||
Bash scripts invoked after system initialization.</para>
|
||||
</listitem>
|
||||
</varlistentry>
|
||||
|
||||
|
||||
<varlistentry>
|
||||
<term><filename>/etc/profile</filename></term>
|
||||
<listitem>
|
||||
<para>systemwide defaults, mostly setting the environment
|
||||
(all Bourne-type shells, not just Bash
|
||||
<footnote><para>This does not apply to <command>csh</command>,
|
||||
<command>tcsh</command>, and other shells not related to or
|
||||
descended from the classic Bourne shell
|
||||
(<command>sh</command>).</para></footnote>)</para>
|
||||
</listitem>
|
||||
</varlistentry>
|
||||
|
||||
<varlistentry>
|
||||
<term><filename>/etc/bashrc</filename></term>
|
||||
<listitem>
|
||||
<para>systemwide functions and <link
|
||||
linkend="aliasref">aliases</link> for Bash</para>
|
||||
</listitem>
|
||||
</varlistentry>
|
||||
|
||||
<varlistentry>
|
||||
<term><filename><varname>$HOME</varname>/.bash_profile</filename></term>
|
||||
<listitem>
|
||||
<para>user-specific Bash environmental default settings,
|
||||
found in each user's home directory (the local counterpart
|
||||
to <filename>/etc/profile</filename>)</para>
|
||||
</listitem>
|
||||
</varlistentry>
|
||||
|
||||
<varlistentry>
|
||||
<term><filename><varname>$HOME</varname>/.bashrc</filename></term>
|
||||
<listitem>
|
||||
<para>user-specific Bash init file, found in each user's home
|
||||
directory (the local counterpart to
|
||||
<filename>/etc/bashrc</filename>). Only interactive
|
||||
shells and user scripts read this file. See
|
||||
<xref linkend="sample-bashrc"> for a sample
|
||||
<filename>.bashrc</filename> file.</para>
|
||||
</listitem>
|
||||
</varlistentry>
|
||||
|
||||
</variablelist>
|
||||
|
||||
|
||||
<variablelist id="logoutfileref">
|
||||
<title><anchor id="logoutfileref1">logout file</title>
|
||||
<varlistentry>
|
||||
<term><filename><varname>$HOME</varname>/.bash_logout</filename></term>
|
||||
|
||||
<listitem>
|
||||
<para>user-specific instruction file, found in
|
||||
each user's home directory. Upon exit from a login (Bash)
|
||||
shell, the commands in this file execute.</para>
|
||||
</listitem>
|
||||
|
||||
</varlistentry>
|
||||
</variablelist>
|
||||
|
||||
</chapter> <!-- Files -->
|
||||
|
||||
|
||||
|
||||
<chapter id="devproc">
|
||||
<title>/dev and /proc</title>
|
||||
|
||||
|
|
@ -23260,7 +23324,7 @@ fi</programlisting></para>
|
|||
<term>Uses of <filename>/dev/null</filename></term>
|
||||
<listitem>
|
||||
<para>Think of <filename>/dev/null</filename> as a <quote>black
|
||||
hole</quote>. It is the nearest equivalent to a
|
||||
hole.</quote> It is the nearest equivalent to a
|
||||
write-only file. Everything written to it disappears
|
||||
forever. Attempts to read or output from it result in
|
||||
nothing. Nevertheless, <filename>/dev/null</filename>
|
||||
|
|
@ -23302,7 +23366,7 @@ cat /dev/null > /var/log/wtmp</programlisting>
|
|||
|
||||
<para>Automatically emptying the contents of a logfile
|
||||
(especially good for dealing with those nasty
|
||||
<quote>cookies</quote> sent by Web commercial sites):</para>
|
||||
<quote>cookies</quote> sent by commercial Web sites):</para>
|
||||
|
||||
<example id="cookies">
|
||||
<title>Hiding the cookie jar</title>
|
||||
|
|
@ -24367,8 +24431,8 @@ while [ "$index" -le "$MAXVAL" ]
|
|||
...
|
||||
|
||||
|
||||
E_NOTFOUND=75 # Uppercase for an errorcode,
|
||||
# and name begins with "E_".
|
||||
E_NOTFOUND=75 # Uppercase for an errorcode,
|
||||
# +and name begins with "E_".
|
||||
if [ ! -e "$filename" ]
|
||||
then
|
||||
echo "File $filename not found."
|
||||
|
|
@ -24393,7 +24457,7 @@ favorite_number=$?
|
|||
echo $favorite_number
|
||||
|
||||
|
||||
_uservariable=23 # Permissable, but not recommended.
|
||||
_uservariable=23 # Permissible, but not recommended.
|
||||
# It's better for user-defined variables not to start with an underscore.
|
||||
# Leave that for system variables.</programlisting>
|
||||
</para>
|
||||
|
|
@ -24652,8 +24716,13 @@ fi</programlisting>
|
|||
<programlisting>&loggingwrapper;</programlisting>
|
||||
</example>
|
||||
|
||||
<example id="coltotaler">
|
||||
<example id="prasc">
|
||||
<title> A <command>shell wrapper</command> around an awk script</title>
|
||||
<programlisting>&prasc;</programlisting>
|
||||
</example>
|
||||
|
||||
<example id="coltotaler">
|
||||
<title> A <command>shell wrapper</command> around another awk script</title>
|
||||
<programlisting>&coltotaler;</programlisting>
|
||||
</example>
|
||||
|
||||
|
|
@ -25319,8 +25388,8 @@ exit 0</programlisting>
|
|||
|
||||
}
|
||||
|
||||
newstring=`capitalize_ichar "each sentence should start with a capital letter."`
|
||||
echo "$newstring" # Each sentence should start with a capital letter.</programlisting>
|
||||
newstring=`capitalize_ichar "every sentence should start with a capital letter."`
|
||||
echo "$newstring" # Every sentence should start with a capital letter.</programlisting>
|
||||
</para>
|
||||
|
||||
<para>It is even possible for a function to <quote>return</quote>
|
||||
|
|
@ -25375,7 +25444,7 @@ echo "$newstring" # Each sentence should start with a capital letter.</
|
|||
<varname>$PATH</varname> and <command>umask</command>.
|
||||
<programlisting>#!/bin/bash
|
||||
PATH=/bin:/usr/bin:/usr/local/bin ; export PATH
|
||||
umask 022
|
||||
umask 022 # Files that the script creates will have 755 permission.
|
||||
|
||||
# Thanks to Ian D. Allen, for this tip.</programlisting></para>
|
||||
</listitem>
|
||||
|
|
@ -25814,6 +25883,9 @@ else
|
|||
# Or, ask for corrected input.
|
||||
fi</programlisting></para>
|
||||
|
||||
<para>For another example of using the <command>=~</command>
|
||||
operator, see <xref linkend="whx">.</para>
|
||||
|
||||
|
||||
</listitem>
|
||||
|
||||
|
|
@ -26108,14 +26180,14 @@ fi</programlisting></para>
|
|||
Chris Martin, Lee Maschmeyer, Bruno Haible, Wilbert Berendsen,
|
||||
Sebastien Godard, Bjön Eriksson, 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, Bruno de Oliveira Schneider, Stefano Falsetto,
|
||||
Chris Morgan, Linc Fessenden, Mariusz Gniazdowski, and David
|
||||
Lawyer (himself an author of four HOWTOs).</para>
|
||||
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,
|
||||
Bruno de Oliveira Schneider, Stefano Falsetto, Chris Morgan,
|
||||
Walter Dnes, Linc Fessenden, Fabian Kreutz, Mariusz Gniazdowski,
|
||||
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>,
|
||||
|
|
@ -27128,6 +27200,15 @@ fi</programlisting></para>
|
|||
<programlisting>&isspammer2;</programlisting>
|
||||
</example>
|
||||
|
||||
|
||||
<para>Another anti-spam script.</para>
|
||||
|
||||
<example id="whx">
|
||||
<title>Spammer Hunt</title>
|
||||
<programlisting>&whx;</programlisting>
|
||||
</example>
|
||||
|
||||
|
||||
<para><quote>Little Monster's</quote> front end to <link
|
||||
linkend="wgetref">wget</link>.</para>
|
||||
|
||||
|
|
@ -28089,6 +28170,7 @@ pattern=BEGIN
|
|||
<listitem><para><xref linkend="lifeslow"></para></listitem>
|
||||
<listitem><para><xref linkend="selfdocument"></para></listitem>
|
||||
<listitem><para><xref linkend="dictlookup"></para></listitem>
|
||||
<listitem><para><xref linkend="whx"></para></listitem>
|
||||
</orderedlist>
|
||||
</para>
|
||||
|
||||
|
|
@ -28111,7 +28193,7 @@ pattern=BEGIN
|
|||
for shell scripting.</para>
|
||||
|
||||
<para>Awk breaks each line of input passed to it into
|
||||
<emphasis>fields</emphasis>. By default, a field is
|
||||
<firstterm>fields</firstterm>. By default, a field is
|
||||
a string of consecutive characters separated by <link
|
||||
linkend="whitespaceref">whitespace</link>, though there are
|
||||
options for changing the delimiter. Awk parses and operates on
|
||||
|
|
@ -28122,7 +28204,14 @@ pattern=BEGIN
|
|||
<para>Strong quoting (single quotes) and curly brackets enclose
|
||||
segments of awk code within a shell script.</para>
|
||||
|
||||
<para><programlisting>awk '{print $3}' $filename
|
||||
<para><programlisting>echo one two | awk '{print $1}'
|
||||
# one
|
||||
|
||||
echo one two | awk '{print $2}'
|
||||
# two
|
||||
|
||||
|
||||
awk '{print $3}' $filename
|
||||
# Prints field #3 of file $filename to stdout.
|
||||
|
||||
awk '{print $1 $5 $6}' $filename
|
||||
|
|
@ -28169,6 +28258,7 @@ awk '{print $1 $5 $6}' $filename
|
|||
<listitem><para><xref linkend="substringex"></para></listitem>
|
||||
<listitem><para><xref linkend="sumproduct"></para></listitem>
|
||||
<listitem><para><xref linkend="userlist"></para></listitem>
|
||||
<listitem><para><xref linkend="prasc"></para></listitem>
|
||||
</orderedlist>
|
||||
</para>
|
||||
|
||||
|
|
@ -28204,79 +28294,82 @@ awk '{print $1 $5 $6}' $filename
|
|||
<tbody>
|
||||
<row>
|
||||
<entry><option>1</option></entry>
|
||||
<entry>catchall for general errors</entry>
|
||||
<entry>Catchall for general errors</entry>
|
||||
<entry>let "var1 = 1/0"</entry>
|
||||
<entry>miscellaneous errors, such as <quote>divide by
|
||||
<entry>Miscellaneous errors, such as <quote>divide by
|
||||
zero</quote></entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>2</option></entry>
|
||||
<entry>misuse of shell builtins, according to Bash documentation</entry>
|
||||
<entry>Misuse of shell builtins (according to Bash documentation)</entry>
|
||||
<entry></entry>
|
||||
<entry>Seldom seen, usually defaults to exit code 1</entry>
|
||||
<entry>Seldom seen, usually defaults to exit code
|
||||
<errorcode>1</errorcode></entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>126</option></entry>
|
||||
<entry>command invoked cannot execute</entry>
|
||||
<entry>Command invoked cannot execute</entry>
|
||||
<entry></entry>
|
||||
<entry>permission problem or command is not an executable</entry>
|
||||
<entry>Permission problem or command is not an executable</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>127</option></entry>
|
||||
<entry><quote>command not found</quote></entry>
|
||||
<entry></entry>
|
||||
<entry>possible problem with <varname>$PATH</varname> or a typo</entry>
|
||||
<entry>Possible problem with <varname>$PATH</varname> or a typo</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>128</option></entry>
|
||||
<entry>invalid argument to <link linkend="exitcommandref">exit</link></entry>
|
||||
<entry>Invalid argument to <link linkend="exitcommandref">exit</link></entry>
|
||||
<entry>exit 3.14159</entry>
|
||||
<entry><command>exit</command> takes only integer args in the
|
||||
range 0 - 255 (see footnote)</entry>
|
||||
range <returnvalue>0 - 255</returnvalue> (see
|
||||
footnote)</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>128+n</option></entry>
|
||||
<entry>fatal error signal <quote>n</quote></entry>
|
||||
<entry>Fatal error signal <quote>n</quote></entry>
|
||||
<entry><command>kill -9</command> <varname>$PPID</varname> of script</entry>
|
||||
<entry><userinput>$?</userinput> returns 137 (128 + 9)</entry>
|
||||
<entry><userinput>$?</userinput> returns
|
||||
<errorcode>137</errorcode> (128 + 9)</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>130</option></entry>
|
||||
<entry>script terminated by Control-C</entry>
|
||||
<entry>Script terminated by Control-C</entry>
|
||||
<entry></entry>
|
||||
<entry>Control-C is fatal error signal 2, (130 = 128 + 2,
|
||||
see above)</entry>
|
||||
<entry>Control-C is fatal error signal
|
||||
<errorcode>2</errorcode>, (130 = 128 + 2, see above)</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>255*</option></entry>
|
||||
<entry>exit status out of range</entry>
|
||||
<entry>exit -1</entry>
|
||||
<entry>Exit status out of range</entry>
|
||||
<entry>exit <returnvalue>-1</returnvalue></entry>
|
||||
<entry><command>exit</command> takes only integer args in the
|
||||
range 0 - 255</entry>
|
||||
range <errorcode>0 - 255</errorcode></entry>
|
||||
</row>
|
||||
</tbody>
|
||||
</tgroup>
|
||||
</table>
|
||||
|
||||
<para>According to the table, exit codes <returnvalue>1 - 2, 126 -
|
||||
165, and 255</returnvalue>
|
||||
<para>According to the above table, exit codes <errorcode>1 - 2,
|
||||
126 - 165, and 255</errorcode>
|
||||
|
||||
<footnote><para>Out of range exit values can result in
|
||||
unexpected exit codes. An exit value greater than
|
||||
<returnvalue>255</returnvalue> returns an exit code modulo
|
||||
256. For example, <command>exit 3809</command> gives an
|
||||
exit code of <errorcode>225</errorcode> (3809 % 256 =
|
||||
225).</para></footnote>
|
||||
unexpected exit codes. An exit value greater
|
||||
than <errorcode>255</errorcode> returns an exit
|
||||
code <link linkend="moduloref">modulo</link>
|
||||
<errorcode>256</errorcode>. For example, <command>exit
|
||||
3809</command> gives an exit code of <errorcode>225</errorcode>
|
||||
(3809 % 256 = 225).</para></footnote>
|
||||
|
||||
have special meanings, and should therefore be avoided as
|
||||
have special meanings, and should therefore be avoided for
|
||||
user-specified exit parameters. Ending a script with <command>exit
|
||||
127</command> would certainly cause confusion when troubleshooting
|
||||
(is the error a <quote>command not found</quote> or a
|
||||
(is the error code a <quote>command not found</quote> or a
|
||||
user-defined one?). However, many scripts use an <command>exit
|
||||
1</command> as a general bailout upon error. Since exit code
|
||||
<returnvalue>1</returnvalue> signifies so many possible errors,
|
||||
this might not add any additional ambiguity, but, on the other
|
||||
hand, it probably would not be very informative either.</para>
|
||||
<errorcode>1</errorcode> signifies so many possible errors,
|
||||
this probably would not be helpful in debugging.</para>
|
||||
|
||||
<para>There has been an attempt to systematize exit status numbers
|
||||
(see <filename
|
||||
|
|
@ -28565,6 +28658,88 @@ exit 0</programlisting>
|
|||
<!-- End Standard Command-Line Options appendix -->
|
||||
|
||||
|
||||
<appendix id="files">
|
||||
<title> Important Files</title>
|
||||
|
||||
<variablelist id="filesref">
|
||||
<title><anchor id="filesref1">startup files</title>
|
||||
|
||||
<varlistentry>
|
||||
<term></term>
|
||||
<listitem>
|
||||
<para>These files contain the aliases and <link
|
||||
linkend="envref">environmental variables</link>
|
||||
made available to Bash running as a user shell and to all
|
||||
Bash scripts invoked after system initialization.</para>
|
||||
</listitem>
|
||||
</varlistentry>
|
||||
|
||||
|
||||
<varlistentry>
|
||||
<term><filename>/etc/profile</filename></term>
|
||||
<listitem>
|
||||
<para>systemwide defaults, mostly setting the environment
|
||||
(all Bourne-type shells, not just Bash
|
||||
<footnote><para>This does not apply to <command>csh</command>,
|
||||
<command>tcsh</command>, and other shells not related to or
|
||||
descended from the classic Bourne shell
|
||||
(<command>sh</command>).</para></footnote>)</para>
|
||||
</listitem>
|
||||
</varlistentry>
|
||||
|
||||
<varlistentry>
|
||||
<term><filename>/etc/bashrc</filename></term>
|
||||
<listitem>
|
||||
<para>systemwide functions and <link
|
||||
linkend="aliasref">aliases</link> for Bash</para>
|
||||
</listitem>
|
||||
</varlistentry>
|
||||
|
||||
<varlistentry>
|
||||
<term><filename><varname>$HOME</varname>/.bash_profile</filename></term>
|
||||
<listitem>
|
||||
<para>user-specific Bash environmental default settings,
|
||||
found in each user's home directory (the local counterpart
|
||||
to <filename>/etc/profile</filename>)</para>
|
||||
</listitem>
|
||||
</varlistentry>
|
||||
|
||||
<varlistentry>
|
||||
<term><filename><varname>$HOME</varname>/.bashrc</filename></term>
|
||||
<listitem>
|
||||
<para>user-specific Bash init file, found in each user's home
|
||||
directory (the local counterpart to
|
||||
<filename>/etc/bashrc</filename>). Only interactive
|
||||
shells and user scripts read this file. See
|
||||
<xref linkend="sample-bashrc"> for a sample
|
||||
<filename>.bashrc</filename> file.</para>
|
||||
</listitem>
|
||||
</varlistentry>
|
||||
|
||||
</variablelist>
|
||||
|
||||
|
||||
<variablelist id="logoutfileref">
|
||||
<title><anchor id="logoutfileref1">logout file</title>
|
||||
<varlistentry>
|
||||
<term><filename><varname>$HOME</varname>/.bash_logout</filename></term>
|
||||
|
||||
<listitem>
|
||||
<para>user-specific instruction file, found in
|
||||
each user's home directory. Upon exit from a login (Bash)
|
||||
shell, the commands in this file execute.</para>
|
||||
</listitem>
|
||||
|
||||
</varlistentry>
|
||||
</variablelist>
|
||||
|
||||
</appendix>
|
||||
<!-- End Files appendix -->
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
<appendix id="systemdirs">
|
||||
|
||||
<title>Important System Directories</title>
|
||||
|
|
@ -30571,6 +30746,11 @@ fairly detailed rundown on the Playfair Cipher and its solution methods.</progra
|
|||
<entry>08 May 2005</entry>
|
||||
<entry>TEABERRY release: Bugfixes, stylistic revisions.</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>3.5</option></entry>
|
||||
<entry>05 Jun 2005</entry>
|
||||
<entry>BOXBERRY release: Bugfixes, some materials added.</entry>
|
||||
</row>
|
||||
</tbody>
|
||||
</tgroup>
|
||||
</table>
|
||||
|
|
@ -30597,7 +30777,7 @@ fairly detailed rundown on the Playfair Cipher and its solution methods.</progra
|
|||
also mirrors the <emphasis>ABS Guide</emphasis>.</para>
|
||||
|
||||
<para>Yet another mirror site for this document is
|
||||
<ulink url="ftp://ftp.morethan.org">the morethan.org ftp site</ulink>.</para>
|
||||
<ulink url="http://www.morethan.org">morethan.org</ulink>.</para>
|
||||
|
||||
|
||||
</appendix> <!-- Mirror Sites appendix -->
|
||||
|
|
|
|||
|
|
@ -3,13 +3,15 @@
|
|||
|
||||
# Find anagrams of...
|
||||
LETTERSET=etaoinshrdlu
|
||||
FILTER='.......' # How many letters minimum?
|
||||
# 1234567
|
||||
|
||||
anagram "$LETTERSET" | # Find all anagrams of the letterset...
|
||||
grep '.......' | # With at least 7 letters,
|
||||
grep "$FILTER" | # With at least 7 letters,
|
||||
grep '^is' | # starting with 'is'
|
||||
grep -v 's$' | # no plurals
|
||||
grep -v 'ed$' # no past tense verbs
|
||||
# Possible to add many combinations of conditions.
|
||||
# Possible to add many combinations of conditions and filters.
|
||||
|
||||
# Uses "anagram" utility
|
||||
#+ that is part of the author's "yawl" word list package.
|
||||
|
|
@ -18,8 +20,20 @@ grep -v 'ed$' # no past tense verbs
|
|||
|
||||
exit 0 # End of code.
|
||||
|
||||
|
||||
bash$ sh agram.sh
|
||||
islander
|
||||
isolate
|
||||
isolead
|
||||
isotheral
|
||||
|
||||
|
||||
|
||||
# Exercises:
|
||||
# ---------
|
||||
# Modify this script to take the LETTERSET as a command-line parameter.
|
||||
# Parameterize the filters in lines 11 - 13 (as with $FILTER),
|
||||
#+ so that they can be specified by passing arguments to a function.
|
||||
|
||||
# For a slightly different approach to anagramming,
|
||||
#+ see the agram2.sh script.
|
||||
|
|
|
|||
|
|
@ -4,8 +4,8 @@ ARGS=1 # Number of arguments expected.
|
|||
E_BADARGS=65 # Exit value if incorrect number of args passed.
|
||||
|
||||
test $# -ne $ARGS && echo "Usage: `basename $0` $ARGS argument(s)" && exit $E_BADARGS
|
||||
# If condition-1 true (wrong number of args passed to script),
|
||||
# then the rest of the line executes, and script terminates.
|
||||
# If condition 1 tests true (wrong number of args passed to script),
|
||||
#+ then the rest of the line executes, and script terminates.
|
||||
|
||||
# Line below executes only if the above test fails.
|
||||
echo "Correct number of arguments passed to this script."
|
||||
|
|
|
|||
|
|
@ -14,7 +14,7 @@ var1=2367
|
|||
echo "var1 declared as $var1"
|
||||
var1=var1+1 # Integer declaration eliminates the need for 'let'.
|
||||
echo "var1 incremented by 1 is $var1."
|
||||
# Attempt to change variable declared as integer
|
||||
# Attempt to change variable declared as integer.
|
||||
echo "Attempting to change var1 to floating point value, 2367.1."
|
||||
var1=2367.1 # Results in error message, with no change to variable.
|
||||
echo "var1 is still $var1"
|
||||
|
|
|
|||
|
|
@ -31,8 +31,8 @@ echo "Random number less than $RANGE --- $number"
|
|||
|
||||
echo
|
||||
|
||||
# If you need a random int greater than a lower bound,
|
||||
# then set up a test to discard all numbers below that.
|
||||
# If you need a random integer greater than a lower bound,
|
||||
#+ then set up a test to discard all numbers below that.
|
||||
|
||||
FLOOR=200
|
||||
|
||||
|
|
@ -56,6 +56,7 @@ echo "Random number between $FLOOR and $RANGE --- $number"
|
|||
echo
|
||||
|
||||
|
||||
|
||||
# Generate binary choice, that is, "true" or "false" value.
|
||||
BINARY=2
|
||||
T=1
|
||||
|
|
@ -74,12 +75,13 @@ fi
|
|||
echo
|
||||
|
||||
|
||||
# Generate toss of the dice.
|
||||
# Generate a toss of the dice.
|
||||
SPOTS=6 # Modulo 6 gives range 0 - 5.
|
||||
# Incrementing by 1 gives desired range of 1 - 6.
|
||||
# Thanks, Paulo Marcel Coelho Aragao, for the simplification.
|
||||
die1=0
|
||||
die2=0
|
||||
# Would it be better to just set SPOTS=7 and not add 1? Why or why not?
|
||||
|
||||
# Tosses each die separately, and so gives correct odds.
|
||||
|
||||
|
|
@ -88,6 +90,7 @@ die2=0
|
|||
# Which arithmetic operation, above, has greater precedence --
|
||||
#+ modulo (%) or addition (+)?
|
||||
|
||||
|
||||
let "throw = $die1 + $die2"
|
||||
echo "Throw of the dice = $throw"
|
||||
echo
|
||||
|
|
|
|||
|
|
@ -1,12 +1,12 @@
|
|||
#!/bin/bash
|
||||
|
||||
echo
|
||||
|
||||
# Equivalent to:
|
||||
while [ "$var1" != "end" ] # while test "$var1" != "end"
|
||||
do # also works.
|
||||
do
|
||||
echo "Input variable #1 (end to exit) "
|
||||
read var1 # Not 'read $var1' (why?).
|
||||
echo "variable #1 = $var1" # Need quotes because of "#".
|
||||
echo "variable #1 = $var1" # Need quotes because of "#" . . .
|
||||
# If input is 'end', echoes it here.
|
||||
# Does not test for termination condition until top of loop.
|
||||
echo
|
||||
|
|
|
|||
|
|
@ -16,3 +16,7 @@ tr a-z A-Z <"$1"
|
|||
# Thanks, S.C.
|
||||
|
||||
exit 0
|
||||
|
||||
# Exercise:
|
||||
# Rewrite this script to give the option of changing a file
|
||||
#+ to *either* upper or lowercase.
|
||||
|
|
|
|||
|
|
@ -6,14 +6,14 @@
|
|||
# Try it with one two-word quoted command line parameter,
|
||||
# ./scriptname "Mortimer Jones"
|
||||
|
||||
CMDLINEPARAM=1 # Expect at least command line parameter.
|
||||
CMDLINEPARAM=1 # Expect at least command line parameter.
|
||||
|
||||
if [ $# -ge $CMDLINEPARAM ]
|
||||
then
|
||||
NAME=$1 # If more than one command line param,
|
||||
# then just take the first.
|
||||
NAME=$1 # If more than one command line param,
|
||||
#+ then just take the first.
|
||||
else
|
||||
NAME="John Doe" # Default, if no command line parameter.
|
||||
NAME="John Doe" # Default, if no command line parameter.
|
||||
fi
|
||||
|
||||
RESPONDENT="the author of this fine script"
|
||||
|
|
|
|||
|
|
@ -15,3 +15,6 @@ echo "Second line in $File is:"
|
|||
echo "$line2"
|
||||
|
||||
exit 0
|
||||
|
||||
# Now, how do you parse the separate fields of each line?
|
||||
# Hint: use awk.
|
||||
|
|
|
|||
|
|
@ -2,6 +2,7 @@
|
|||
# $Id$
|
||||
# Script to perform batch anonymous ftp. Essentially converts a list of
|
||||
# of command line arguments into input to ftp.
|
||||
# ==> This script is nothing but a shell wrapper around "ftp" . . .
|
||||
# Simple, and quick - written as a companion to ftplist
|
||||
# -h specifies the remote host (default prep.ai.mit.edu)
|
||||
# -d specifies the remote directory to cd to - you can provide a sequence
|
||||
|
|
@ -24,8 +25,7 @@
|
|||
# Obviously, the sequence of the options is important, since the equivalent
|
||||
# commands are executed by ftp in corresponding order
|
||||
#
|
||||
# Mark Moraes (moraes@csri.toronto.edu), Feb 1, 1989
|
||||
# ==> Angle brackets changed to parens, so Docbook won't get indigestion.
|
||||
# Mark Moraes <moraes@csri.toronto.edu>, Feb 1, 1989
|
||||
#
|
||||
|
||||
|
||||
|
|
@ -35,6 +35,8 @@
|
|||
# export PATH
|
||||
# ==> Above 2 lines from original script probably superfluous.
|
||||
|
||||
E_BADARGS=65
|
||||
|
||||
TMPFILE=/tmp/ftp.$$
|
||||
# ==> Creates temp file, using process id of script ($$)
|
||||
# ==> to construct filename.
|
||||
|
|
@ -51,10 +53,11 @@ set -f # So we can use globbing in -m
|
|||
set x `getopt vh:d:c:m:f: $*`
|
||||
if [ $? != 0 ]; then
|
||||
echo $usage
|
||||
exit 65
|
||||
exit $E_BADARGS
|
||||
fi
|
||||
shift
|
||||
trap 'rm -f ${TMPFILE} ; exit' 0 1 2 3 15
|
||||
# ==> Delete tempfile in case of abnormal exit from script.
|
||||
echo "user anonymous ${USER-gnu}@${SITE} > ${TMPFILE}"
|
||||
# ==> Added quotes (recommended in complex echoes).
|
||||
echo binary >> ${TMPFILE}
|
||||
|
|
@ -74,17 +77,19 @@ do
|
|||
echo get ${f1} ${f2} >> ${TMPFILE}; shift 2;;
|
||||
--) shift; break;;
|
||||
esac
|
||||
# ==> 'lcd' and 'mget' are ftp commands. See "man ftp" . . .
|
||||
done
|
||||
if [ $# -ne 0 ]; then
|
||||
echo $usage
|
||||
exit 65 # ==> Changed from "exit 2" to conform with standard.
|
||||
exit $E_BADARGS
|
||||
# ==> Changed from "exit 2" to conform with style standard.
|
||||
fi
|
||||
if [ x${verbflag} != x ]; then
|
||||
ftpflags="${ftpflags} -v"
|
||||
fi
|
||||
if [ x${remhost} = x ]; then
|
||||
remhost=prep.ai.mit.edu
|
||||
# ==> Rewrite to match your favorite ftp site.
|
||||
# ==> Change to match appropriate ftp site.
|
||||
fi
|
||||
echo quit >> ${TMPFILE}
|
||||
# ==> All commands saved in tempfile.
|
||||
|
|
|
|||
|
|
@ -12,7 +12,9 @@
|
|||
# Slightly modified and commented by ABS author.
|
||||
|
||||
#=================================================================#
|
||||
# The Tower of Hanoi is an old mathematical puzzle.
|
||||
# The Tower of Hanoi is a mathematical puzzle attributed to
|
||||
#+ Edouard Lucas, a nineteenth-century French mathematician.
|
||||
#
|
||||
# There are three vertical posts set in a base.
|
||||
# The first post has a set of annular rings stacked on it.
|
||||
# These rings are flat disks with a hole drilled out of the center,
|
||||
|
|
|
|||
|
|
@ -38,23 +38,23 @@ No_WSP=$'\x0A'$'\x0D'
|
|||
# Field separator for dotted decimal ip addresses
|
||||
ADR_IFS=${No_WSP}'.'
|
||||
|
||||
# Get the dns text resource record
|
||||
# Get the dns text resource record.
|
||||
# get_txt <error_code> <list_query>
|
||||
get_txt() {
|
||||
|
||||
# parse $1 by assignment at the dots
|
||||
# Parse $1 by assignment at the dots.
|
||||
local -a dns
|
||||
IFS=$ADR_IFS
|
||||
dns=( $1 )
|
||||
IFS=$WSP_IFS
|
||||
if [ "${dns[0]}" == '127' ]
|
||||
then
|
||||
# see if there is a reason
|
||||
# See if there is a reason.
|
||||
echo $(dig +short $2 -t txt)
|
||||
fi
|
||||
}
|
||||
|
||||
# Get the dns address resource record
|
||||
# Get the dns address resource record.
|
||||
# chk_adr <rev_dns> <list_server>
|
||||
chk_adr() {
|
||||
local reply
|
||||
|
|
@ -64,7 +64,7 @@ chk_adr() {
|
|||
server=${1}${2}
|
||||
reply=$( dig +short ${server} )
|
||||
|
||||
# if reply might be an error code . . .
|
||||
# If reply might be an error code . . .
|
||||
if [ ${#reply} -gt 6 ]
|
||||
then
|
||||
reason=$(get_txt ${reply} ${server} )
|
||||
|
|
|
|||
|
|
@ -3,7 +3,7 @@
|
|||
# $Id$
|
||||
# Above line is RCS info.
|
||||
|
||||
# The latest version of this script is available from ftp://ftp.morethan.org.
|
||||
# The latest version of this script is available from http://www.morethan.org.
|
||||
#
|
||||
# Spammer-identification
|
||||
# by Michael S. Zick
|
||||
|
|
@ -172,7 +172,7 @@ pend_dummy() { : ; }
|
|||
pend_init() {
|
||||
unset _pending_[@]
|
||||
pend_func pend_stop_mark
|
||||
_pend_hook_='pend_dummy' # Debug only
|
||||
_pend_hook_='pend_dummy' # Debug only.
|
||||
}
|
||||
|
||||
# Discard the top function on the stack.
|
||||
|
|
@ -211,7 +211,7 @@ pend_release() {
|
|||
_top_=${#_pending_[@]}-1
|
||||
_pend_current_=${_pending_[$_top_]}
|
||||
unset _pending_[$_top_]
|
||||
$_pend_hook_ # Debug only
|
||||
$_pend_hook_ # Debug only.
|
||||
eval $_pend_current_
|
||||
done
|
||||
}
|
||||
|
|
@ -969,7 +969,7 @@ name_fixup(){
|
|||
IFS=${WSP_IFS}
|
||||
_nf_end=${#_nf_tmp[@]}
|
||||
case ${_nf_end} in
|
||||
0) # No dots, only dots
|
||||
0) # No dots, only dots.
|
||||
echo
|
||||
return 1
|
||||
;;
|
||||
|
|
|
|||
|
|
@ -1,10 +1,10 @@
|
|||
#! /bin/bash
|
||||
#!/bin/bash
|
||||
#
|
||||
# Changes every filename in working directory to all lowercase.
|
||||
# Changes every filename in working directory to all lowercase.
|
||||
#
|
||||
# Inspired by a script of John Dubois,
|
||||
# which was translated into into Bash by Chet Ramey,
|
||||
# and considerably simplified by Mendel Cooper, author of this document.
|
||||
# Inspired by a script of John Dubois,
|
||||
#+ which was translated into Bash by Chet Ramey,
|
||||
#+ and considerably simplified by the author of the ABS Guide.
|
||||
|
||||
|
||||
for filename in * # Traverse all files in directory.
|
||||
|
|
@ -17,7 +17,7 @@ do
|
|||
fi
|
||||
done
|
||||
|
||||
exit 0
|
||||
exit $?
|
||||
|
||||
|
||||
# Code below this line will not execute because of "exit".
|
||||
|
|
@ -25,7 +25,6 @@ exit 0
|
|||
# To run it, delete script above line.
|
||||
|
||||
# The above script will not work on filenames containing blanks or newlines.
|
||||
|
||||
# Stephane Chazelas therefore suggests the following alternative:
|
||||
|
||||
|
||||
|
|
@ -41,4 +40,4 @@ do n=`echo "$filename/" | tr '[:upper:]' '[:lower:]'`
|
|||
# Checks if filename already lowercase.
|
||||
done
|
||||
|
||||
exit 0
|
||||
exit $?
|
||||
|
|
|
|||
|
|
@ -34,9 +34,11 @@ echo $retval # Echoes (to stdout), rather than returning value.
|
|||
|
||||
|
||||
return_val=$(max2 33001 33997)
|
||||
# ^^^^ Function name
|
||||
# ^^^^^ ^^^^^ Params passed
|
||||
# This is actually a form of command substitution:
|
||||
#+ treating a function as if it were a command,
|
||||
#+ and assigning the stdout of the function to the variable 'return_val.'
|
||||
#+ and assigning the stdout of the function to the variable "return_val."
|
||||
|
||||
|
||||
# ========================= OUTPUT ========================
|
||||
|
|
|
|||
|
|
@ -1,6 +1,8 @@
|
|||
#!/bin/bash
|
||||
# logon.sh: A quick 'n dirty script to check whether you are on-line yet.
|
||||
|
||||
umask 177 # Make sure temp files are not world readable.
|
||||
|
||||
|
||||
TRUE=1
|
||||
LOGFILE=/var/log/messages
|
||||
|
|
@ -8,6 +10,9 @@ LOGFILE=/var/log/messages
|
|||
#+ (as root, chmod 644 /var/log/messages).
|
||||
TEMPFILE=temp.$$
|
||||
# Create a "unique" temp file name, using process id of the script.
|
||||
# Using 'mktemp' is an alternative.
|
||||
# For example:
|
||||
# TEMPFILE=`mktemp temp.XXXXXX`
|
||||
KEYWORD=address
|
||||
# At logon, the line "remote IP address xxx.xxx.xxx.xxx"
|
||||
# appended to /var/log/messages.
|
||||
|
|
|
|||
|
|
@ -2,7 +2,7 @@
|
|||
# pb.sh: phone book
|
||||
|
||||
# Written by Rick Boivie, and used with permission.
|
||||
# Modifications by document author.
|
||||
# Modifications by ABS Guide author.
|
||||
|
||||
MINARGS=1 # Script needs at least one argument.
|
||||
DATAFILE=./phonebook
|
||||
|
|
|
|||
|
|
@ -9,12 +9,12 @@
|
|||
# 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",
|
||||
# p. 137, ff.
|
||||
# See Hofstadter's book, "Goedel, Escher, Bach: An Eternal Golden Braid",
|
||||
#+ p. 137, ff.
|
||||
|
||||
|
||||
LIMIT=100 # Number of terms to calculate
|
||||
LINEWIDTH=20 # Number of terms printed per line
|
||||
LIMIT=100 # Number of terms to calculate.
|
||||
LINEWIDTH=20 # Number of terms printed per line.
|
||||
|
||||
Q[1]=1 # First two terms of series are 1.
|
||||
Q[2]=1
|
||||
|
|
@ -26,8 +26,8 @@ echo -n "${Q[2]} "
|
|||
|
||||
for ((n=3; n <= $LIMIT; n++)) # C-like loop conditions.
|
||||
do # Q[n] = Q[n - Q[n-1]] + Q[n - Q[n-2]] for n>2
|
||||
# Need to break the expression into intermediate terms,
|
||||
# since Bash doesn't handle complex array arithmetic very well.
|
||||
# Need to break the expression into intermediate terms,
|
||||
#+ since Bash doesn't handle complex array arithmetic very well.
|
||||
|
||||
let "n1 = $n - 1" # n-1
|
||||
let "n2 = $n - 2" # n-2
|
||||
|
|
@ -42,7 +42,7 @@ Q[n]=`expr $T0 + $T1` # Q[n - Q[n-1]] + Q[n - Q[n-2]]
|
|||
echo -n "${Q[n]} "
|
||||
|
||||
if [ `expr $n % $LINEWIDTH` -eq 0 ] # Format output.
|
||||
then # mod
|
||||
then # ^ Modula operator
|
||||
echo # Break lines into neat chunks.
|
||||
fi
|
||||
|
||||
|
|
@ -54,4 +54,4 @@ exit 0
|
|||
|
||||
# This is an iterative implementation of the Q-series.
|
||||
# The more intuitive recursive implementation is left as an exercise.
|
||||
# Warning: calculating this series recursively takes a *very* long time.
|
||||
# Warning: calculating this series recursively takes a VERY long time.
|
||||
|
|
|
|||
|
|
@ -4,15 +4,15 @@ echo
|
|||
|
||||
echo "Enter a string terminated by a \\, then press <ENTER>."
|
||||
echo "Then, enter a second string, and again press <ENTER>."
|
||||
read var1 # The "\" suppresses the newline, when reading "var1".
|
||||
read var1 # The "\" suppresses the newline, when reading $var1.
|
||||
# first line \
|
||||
# second line
|
||||
|
||||
echo "var1 = $var1"
|
||||
# var1 = first line second line
|
||||
|
||||
# For each line terminated by a "\",
|
||||
# you get a prompt on the next line to continue feeding characters into var1.
|
||||
# For each line terminated by a "\"
|
||||
#+ you get a prompt on the next line to continue feeding characters into var1.
|
||||
|
||||
echo; echo
|
||||
|
||||
|
|
|
|||
|
|
@ -1,6 +1,7 @@
|
|||
#!/bin/bash
|
||||
# Starting the script with "#!/bin/bash -r"
|
||||
# runs entire script in restricted mode.
|
||||
|
||||
# Starting the script with "#!/bin/bash -r"
|
||||
#+ runs entire script in restricted mode.
|
||||
|
||||
echo
|
||||
|
||||
|
|
|
|||
|
|
@ -58,7 +58,7 @@ do #+ columns vary,
|
|||
done
|
||||
|
||||
# The simpler equivalent is
|
||||
# echo ${alpha[*]} | xargs -n $Columns
|
||||
# echo ${alpha[*]} | xargs -n $Columns
|
||||
|
||||
echo
|
||||
}
|
||||
|
|
@ -67,7 +67,7 @@ filter () # Filter out negative array indices.
|
|||
{
|
||||
|
||||
echo -n " " # Provides the tilt.
|
||||
# Explain why.
|
||||
# Explain how.
|
||||
|
||||
if [[ "$1" -ge 0 && "$1" -lt "$Rows" && "$2" -ge 0 && "$2" -lt "$Columns" ]]
|
||||
then
|
||||
|
|
@ -102,7 +102,8 @@ for (( row = Rows; row > -Rows; row-- ))
|
|||
let "t2 = $column + $row"
|
||||
fi
|
||||
|
||||
filter $t1 $t2 # Filter out negative array indices. Why?
|
||||
filter $t1 $t2 # Filter out negative array indices.
|
||||
# What happens if you don't do this?
|
||||
done
|
||||
|
||||
echo; echo
|
||||
|
|
|
|||
|
|
@ -10,11 +10,22 @@ echo "Just initialized \"\$variable\" to $variable."
|
|||
let "variable *= 3"
|
||||
echo "Just multiplied \"\$variable\" by 3."
|
||||
|
||||
# The "trap 'commands' DEBUG" construct would be more useful
|
||||
# in the context of a complex script,
|
||||
# where placing multiple "echo $variable" statements might be
|
||||
# clumsy and time-consuming.
|
||||
exit $?
|
||||
|
||||
# The "trap 'command1 . . . command2 . . .' DEBUG" construct is
|
||||
#+ more appropriate in the context of a complex script,
|
||||
#+ where placing multiple "echo $variable" statements might be
|
||||
#+ clumsy and time-consuming.
|
||||
|
||||
# Thanks, Stephane Chazelas for the pointer.
|
||||
|
||||
exit 0
|
||||
|
||||
Output of script:
|
||||
|
||||
VARIABLE-TRACE> $variable = ""
|
||||
VARIABLE-TRACE> $variable = "29"
|
||||
Just initialized "$variable" to 29.
|
||||
VARIABLE-TRACE> $variable = "29"
|
||||
VARIABLE-TRACE> $variable = "87"
|
||||
Just multiplied "$variable" by 3.
|
||||
VARIABLE-TRACE> $variable = "87"
|
||||
|
|
|
|||
Loading…
Reference in New Issue