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<H2><A NAME="s7">7. Loops for, while and until</A> </H2>
<P> In this section you'll find for, while and until loops.
<P> The <B>for</B> loop is a little bit different from other programming
languages. Basically, it let's you iterate over a series of
'words' within a string.
<P> The <B>while</B> executes a piece of code if the control expression
is true, and only stops when it is false (or a explicit break is found
within the executed code.
<P> The <B>until</B> loop is almost equal to the while loop, except that
the code is executed while the control expression evaluates to false.
<P> If you suspect that while and until are very similar you are right.
<H2><A NAME="ss7.1">7.1 For sample</A>
</H2>
<P>
<BLOCKQUOTE><CODE>
<PRE>
#!/bin/bash
for i in $( ls ); do
echo item: $i
done
</PRE>
</CODE></BLOCKQUOTE>
<P>
<P> On the second line, we declare i to be the variable that
will take the
different values contained in $( ls ).
<P> The third line could be longer if needed, or there could
be more lines
before the done (4).
<P> 'done' (4) indicates that the code that used the value of $i has
finished and $i can take a new value.
<P> This script has very little sense, but a more useful way to use the
for loop would be to use it to match only certain files on the previous
example
<P>
<H2><A NAME="ss7.2">7.2 C-like for</A>
</H2>
<P> fiesh suggested adding this form of looping. It's a for loop
more similar to C/perl... for.
<BLOCKQUOTE><CODE>
<PRE>
#!/bin/bash
for i in `seq 1 10`;
do
echo $i
done
</PRE>
</CODE></BLOCKQUOTE>
<H2><A NAME="ss7.3">7.3 While sample</A>
</H2>
<P>
<BLOCKQUOTE><CODE>
<PRE>
#!/bin/bash
COUNTER=0
while [ $COUNTER -lt 10 ]; do
echo The counter is $COUNTER
let COUNTER=COUNTER+1
done
</PRE>
</CODE></BLOCKQUOTE>
<P>
<P> This script 'emulates' the well known
(C, Pascal, perl, etc) 'for' structure
<H2><A NAME="ss7.4">7.4 Until sample</A>
</H2>
<P>
<BLOCKQUOTE><CODE>
<PRE>
#!/bin/bash
COUNTER=20
until [ $COUNTER -lt 10 ]; do
echo COUNTER $COUNTER
let COUNTER-=1
done
</PRE>
</CODE></BLOCKQUOTE>
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