bash "do-while" post-test syntax

orange.toaster · 07-07-2009, 11:45 AM

The syntax for a while loop in bash is

Code:

while [ condition ]
do<commands>
done

but what is the equivalent for the c-style

Code:

do
{<commands>
}while(condition);

I can't seem to get the post-test loop syntax working in a bash script.

A possible work around is to use a break:

Code:

while [ 1 ]
do<commands>
<condition> || break
done

I would assume that there must be syntax for a post-test loop in bash.

pixellany · 07-07-2009, 02:20 PM

A quick glance at the ABS** boat anchor says there is no "do....while" construct in BASH. There is an "until" loop which might be useful.

**Advanced BASH Scripting Guide----free at http://tldp.org

GazL · 07-07-2009, 03:02 PM

Quote:

Originally Posted by pixellany

A quick glance at the ABS** boat anchor says there is no "do....while" construct in BASH. There is an "until" loop which might be useful.

**Advanced BASH Scripting Guide----free at http://tldp.org

UNTIL in bash is just a while with the condition negated. So it's logically speaking just a more readable version of.

Code:

while ! condition

It's not like the repeat/until post-test loop construct in Pascal or good old BASIC so it's not a great deal more use than the while.

There doesn't appear to be any post-test loop construct in bash that I can find.

Similar to Orange's example with the break, you could also do it like this, though it's still pretty kludgy.

Code:

while command
do
  continue
done

gapan · 07-07-2009, 04:26 PM

I guess you could also do:

Code:

whatyouwanttodo()
{
<commands>
}

whatyouwanttodo
while [ condition ]
do
  whatyouwanttodo
done