226 lines
3.5 KiB
HTML
226 lines
3.5 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<HTML
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>Nested Loops</TITLE
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TITLE="Loops and Branches"
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>Advanced Bash-Scripting Guide: </TH
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>Chapter 11. Loops and Branches</TD
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><H1
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><A
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NAME="NESTEDLOOPS"
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></A
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>11.2. Nested Loops</H1
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><P
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>A <I
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CLASS="FIRSTTERM"
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>nested loop</I
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> is a loop within a
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loop, an inner loop within the body of an outer one. How
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this works is that the first pass of the outer loop triggers
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the inner loop, which executes to completion. Then the
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second pass of the outer loop triggers the inner loop
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again. This repeats until the outer loop finishes. Of course,
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a <I
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CLASS="FIRSTTERM"
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>break</I
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> within either the inner or outer
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loop would interrupt this process.</P
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><DIV
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CLASS="EXAMPLE"
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><A
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NAME="NESTEDLOOP"
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></A
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><P
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><B
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>Example 11-20. Nested Loop</B
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></P
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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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>#!/bin/bash
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# nested-loop.sh: Nested "for" loops.
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outer=1 # Set outer loop counter.
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# Beginning of outer loop.
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for a in 1 2 3 4 5
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do
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echo "Pass $outer in outer loop."
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echo "---------------------"
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inner=1 # Reset inner loop counter.
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# ===============================================
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# Beginning of inner loop.
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for b in 1 2 3 4 5
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do
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echo "Pass $inner in inner loop."
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let "inner+=1" # Increment inner loop counter.
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done
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# End of inner loop.
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# ===============================================
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let "outer+=1" # Increment outer loop counter.
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echo # Space between output blocks in pass of outer loop.
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done
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# End of outer loop.
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exit 0</PRE
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></FONT
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></TABLE
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></DIV
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><P
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>See <A
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HREF="arrays.html#BUBBLE"
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>Example 27-11</A
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> for an illustration of nested
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<A
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HREF="loops1.html#WHILELOOPREF"
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>while loops</A
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>, and <A
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HREF="arrays.html#EX68"
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>Example 27-13</A
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> to see a while loop nested inside an <A
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HREF="loops1.html#UNTILLOOPREF"
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>until loop</A
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>.</P
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