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>do..while</TITLE
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NAME="control-structures.do.while"
><TT
CLASS="literal"
>do..while</TT
></A
></H1
><P
>&#13;    <TT
CLASS="literal"
>do..while</TT
> loops are very similar to
    <TT
CLASS="literal"
>while</TT
> loops, except the truth expression is
    checked at the end of each iteration instead of in the beginning.
    The main difference from regular <TT
CLASS="literal"
>while</TT
> loops is
    that the first iteration of a <TT
CLASS="literal"
>do..while</TT
> loop is
    guarenteed to run (the truth expression is only checked at the end
    of the iteration), whereas it's may not necessarily run with a
    regular <TT
CLASS="literal"
>while</TT
> loop (the truth expression is
    checked at the beginning of each iteration, if it evaluates to
    <TT
CLASS="literal"
>FALSE</TT
> right from the beginning, the loop
    execution would end immediately).
   </P
><P
>&#13;    There is just one syntax for <TT
CLASS="literal"
>do..while</TT
> loops:
 
    <DIV
CLASS="informalexample"
><A
NAME="AEN3436"
></A
><P
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="programlisting"
>&#13;$i = 0;
do {
   print $i;
} while ($i&#62;0);
     </PRE
></TD
></TR
></TABLE
><P
></P
></DIV
>
   </P
><P
>&#13;     The above loop would run one time exactly, since after the first
     iteration, when truth expression is checked, it evaluates to
     <TT
CLASS="literal"
>FALSE</TT
> ($i is not bigger than 0) and the loop
     execution ends.
   </P
><P
>&#13;    Advanced C users may be familiar with a different usage of the
    <TT
CLASS="literal"
>do..while</TT
> loop, to allow stopping execution in
    the middle of code blocks, by encapsulating them with
    <TT
CLASS="literal"
>do..while</TT
>(0), and using the <A
HREF="control-structures.break.html"
><TT
CLASS="literal"
>break</TT
></A
>
    statement.  The following code fragment demonstrates this:
    <DIV
CLASS="informalexample"
><A
NAME="AEN3445"
></A
><P
></P
><TABLE
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><TD
><PRE
CLASS="programlisting"
>&#13;do {
    if ($i &#60; 5) {
        print "i is not big enough";
        break;
    }
    $i *= $factor;
    if ($i &#60; $minimum_limit) {
        break;
    }
    print "i is ok";

     ...process i...

} while(0);
     </PRE
></TD
></TR
></TABLE
><P
></P
></DIV
>
   </P
><P
>&#13;    Don't worry if you don't understand this right away or at all.
    You can code scripts and even powerful scripts without using this
    `feature'.
   </P
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