198 lines
3.3 KiB
HTML
198 lines
3.3 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<HTML
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>Tests and Comparisons: Alternatives</TITLE
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TITLE="Miscellany"
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>Advanced Bash-Scripting Guide: </TH
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>Chapter 36. Miscellany</TD
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NAME="TESTSANDCOMPARISONS"
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>36.3. Tests and Comparisons: Alternatives</H1
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><P
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>For tests, the <A
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HREF="testconstructs.html#DBLBRACKETS"
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>[[ ]]</A
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>
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construct may be more appropriate than <TT
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CLASS="USERINPUT"
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><B
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>[
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]</B
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></TT
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>. Likewise, <A
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HREF="comparison-ops.html#ICOMPARISON1"
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>arithmetic
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comparisons</A
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> might benefit from the <A
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HREF="dblparens.html"
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>(( ))</A
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> construct.
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<TABLE
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BORDER="0"
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BGCOLOR="#E0E0E0"
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WIDTH="100%"
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><TR
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><TD
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><FONT
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COLOR="#000000"
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><PRE
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CLASS="PROGRAMLISTING"
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>a=8
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# All of the comparisons below are equivalent.
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test "$a" -lt 16 && echo "yes, $a < 16" # "and list"
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/bin/test "$a" -lt 16 && echo "yes, $a < 16"
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[ "$a" -lt 16 ] && echo "yes, $a < 16"
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[[ $a -lt 16 ]] && echo "yes, $a < 16" # Quoting variables within
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(( a < 16 )) && echo "yes, $a < 16" # [[ ]] and (( )) not necessary.
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city="New York"
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# Again, all of the comparisons below are equivalent.
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test "$city" \< Paris && echo "Yes, Paris is greater than $city"
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# Greater ASCII order.
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/bin/test "$city" \< Paris && echo "Yes, Paris is greater than $city"
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[ "$city" \< Paris ] && echo "Yes, Paris is greater than $city"
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[[ $city < Paris ]] && echo "Yes, Paris is greater than $city"
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# Need not quote $city.
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# Thank you, S.C.</PRE
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>Recursion: a script calling itself</TD
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