Crontab entries

[Steven W. Orr]

On Thursday, Feb 16th 2006 at 12:54 -0500, quoth Paul Lussier:

=>Is there a requirement to place parens around a set of commands
=>delimeted by a ';' for crontab entries?
=>
=>At some point I got in the habit of creating entries like:
=>
=>30 02 * * * (foo;bar;baz)
=>
=>But nowhere can I find documentation even mentioning the use of
=>parens. Of course, I haven't even seen mention of having cron exec'ing
=>multiple commands either...
=>
=>Using the parens definitely works, I'm just trying to figure where I
=>picked up that habit...

Parens are one of the two grouping operators. The other is curly braces. 
Note that the syntax for curlys is different than for parens.

{ cmd1; cmd2; cmd3; }

That last semicolon is required.

The functional difference is that parens cause its content to execute in a 
seperate subshell. The only reason to do so is if a command sequence would 
change something about the current environment that subsequent commands 
would not want. e.g., 

pwd		# Here I am
qaz=44		# Here's what it is.
(cd foo; foo=55; bar)
pwd		# I'm still where I started and $foo is still 44.
echo $foo

So the answer is that it is not needed to group your cron entry in parens. 
It just burns an extra shell.

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