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>Advanced Bash-Scripting Guide: An in-depth exploration of the art of shell scripting</TH
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>Chapter 36. Bash, versions 2, 3, and 4</TD
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>36.2. Bash, version 3</H1
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>On July 27, 2004, Chet Ramey released version 3 of Bash.
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This update fixed quite a number of bugs and added new
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>Some of the more important added features:
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>A new, more generalized <B
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HREF="special-chars.html#BRACEEXPREF"
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CLASS="PROGRAMLISTING"
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3 for i in {1..10}
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4 # Simpler and more straightforward than
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5 #+ for i in $(seq 10)
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7 echo -n "$i "
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12 # 1 2 3 4 5 6 7 8 9 10
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16 # Or just . . .
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18 echo {a..z} # a b c d e f g h i j k l m n o p q r s t u v w x y z
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19 echo {e..m} # e f g h i j k l m
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20 echo {z..a} # z y x w v u t s r q p o n m l k j i h g f e d c b a
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21 # Works backwards, too.
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22 echo {25..30} # 25 26 27 28 29 30
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23 echo {3..-2} # 3 2 1 0 -1 -2
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24 echo {X..d} # X Y Z [ ] ^ _ ` a b c d
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25 # Shows (some of) the ASCII characters between Z and a,
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26 #+ but don't rely on this type of behavior because . . .
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27 echo {]..a} # {]..a}
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31 # You can tack on prefixes and suffixes.
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32 echo "Number #"{1..4}, "..."
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33 # Number #1, Number #2, Number #3, Number #4, ...
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36 # You can concatenate brace-expansion sets.
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37 echo {1..3}{x..z}" +" "..."
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38 # 1x + 1y + 1z + 2x + 2y + 2z + 3x + 3y + 3z + ...
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39 # Generates an algebraic expression.
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40 # This could be used to find permutations.
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42 # You can nest brace-expansion sets.
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43 echo {{a..c},{1..3}}
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44 # a b c 1 2 3
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45 # The "comma operator" splices together strings.
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48 # Unfortunately, brace expansion does not lend itself to parameterization.
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51 echo {$var1..$var2} # {1..5}</PRE
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expands to all the indices of a given <A
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HREF="arrays.html#ARRAYREF"
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3 Array=(element-zero element-one element-two element-three)
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5 echo ${Array[0]} # element-zero
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6 # First element of array.
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8 echo ${!Array[@]} # 0 1 2 3
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9 # All the indices of Array.
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11 for i in ${!Array[@]}
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13 echo ${Array[i]} # element-zero
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14 # element-one
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15 # element-two
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16 # element-three
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18 # All the elements in Array.
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HREF="regexp.html#REGEXREF"
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> matching operator within a <A
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(Perl has a similar operator.)</P
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3 variable="This is a fine mess."
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5 echo "$variable"
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7 # Regex matching with =~ operator within [[ double brackets ]].
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8 if [[ "$variable" =~ T.........fin*es* ]]
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9 # NOTE: As of version 3.2 of Bash, expression to match no longer quoted.
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11 echo "match found"
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12 # match found
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>Or, more usefully:</P
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6 if [[ "$input" =~ "[0-9][0-9][0-9]-[0-9][0-9]-[0-9][0-9][0-9][0-9]" ]]
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7 # ^ NOTE: Quoting not necessary, as of version 3.2 of Bash.
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8 # NNN-NN-NNNN (where each N is a digit).
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10 echo "Social Security number."
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11 # Process SSN.
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13 echo "Not a Social Security number!"
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14 # Or, ask for corrected input.
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>For additional examples of using the
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HREF="contributed-scripts.html#WHX"
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HREF="here-docs.html#MAILBOXGREP"
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HREF="contributed-scripts.html#FINDSPLIT"
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HREF="contributed-scripts.html#TOHTML"
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useful for debugging <A
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this option is set, then the <A
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HREF="exit-status.html#EXITSTATUSREF"
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is the exit status of the last command in the pipe to
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> (return a non-zero value), rather
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than the actual final command in the pipe.</P
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HREF="communications.html#FC4UPD"
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SRC="common/caution.png"
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>The update to version 3 of Bash breaks a few scripts
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that worked under earlier versions. <SPAN
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>Test critical legacy
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scripts to make sure they still work!</I
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>As it happens, a couple of the scripts in the
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>Advanced Bash Scripting Guide</I
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HREF="variables2.html#TOUT"
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>36.2.1. Bash, version 3.1</H2
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>The version 3.1 update of Bash introduces a number of bugfixes
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and a few minor changes.</P
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> operator is now permitted in
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in places where previously only the <SPAN
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assignment operator was recognized.</P
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4 a+=5 # Won't work under versions of Bash earlier than 3.1.
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8 echo $a # 15Hello</PRE
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> operator. Note that its behavior
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in this particular context is different than within a
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4 let a+=5 # Integer arithmetic, rather than string concatenation.
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7 let a+=Hello # Doesn't "add" anything to a.
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8 echo $a # 6</PRE
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>36.2.2. Bash, version 3.2</H2
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>This is pretty much a bugfix update.</P
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parameter substitutions</A
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>, the pattern no longer anchors
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at the start of the string.</P
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>process substitution</A
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HREF="quoting.html#QUOTINGREF"
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HREF="tests.html#DBLBRACKETS"
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>In fact, quoting in this context is
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> advisable as it may
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> evaluation to fail.
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Chet Ramey states in the <A
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HREF="biblio.html#BASHFAQ"
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> that quoting explicitly disables regex evaluation.
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HREF="https://bugs.launchpad.net/ubuntu-website/+bug/109931"
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HREF="http://en.wikinerds.org/index.php/Bash_syntax_and_semantics"
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> Wikinerds on Bash syntax</A
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>shopt -s compat31</I
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in a script causes reversion to the original
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>Bash, versions 2, 3, and 4</TD
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