Shell Programming and Scripting

Hi there,

How can I run a script being sure that it runs all the way to the end even if the source file is deleted or replaced while running?
Actually, I have a script that runs daily on several servers. It replaces local files by updates from a master server. But I'd like it to replace itself too if an update is found on the master server.

Here is an example of what happens if a script is replaced while running:

Code:

~# cat script
echo statement 1
cp $0.update $0
echo statement 2
~# cat script.update
echo statement 3
cp $0.update $0
echo statement 4
~# bash script
statement 1
statement 4

How can I make sure the script runs entirely even if replaced while running?
1) The replacement file should not run immediately, this update will run the next day.
2) I would prefer not to have to create temporary files.
3) Although it would be a simple solution, it's hard for me to wait until the end of the script to do the replacement because other tasks run after files are updated.

Thanks in advance
Santiago

it should be posible to replace a script while it is running withou any problem bcs the file is loaded into memory at execution time

Although I'm a newbie, I think the following code clearly shows that this is not the case:

Code:

~# cat script
echo statement 1
cp $0.update $0
echo statement 2
~# cat script.update
echo statement 3
cp $0.update $0
echo statement 4
~# bash script
statement 1
statement 4

Here is a solution that I found,
Tell me if this looks OK.

Code:

~# cat myscript
(( $inside )) || { inside=1; . "$0"; exit; }
echo statement 1
cp $0.update $0
echo statement 2
~# cat myscript.update
(( $inside )) || { inside=1; . "$0"; exit; }
echo statement 3
cp $0.update $0
echo statement 4
~# myscript
statement 1
statement 2
~# myscript
statement 3
statement 4