Hello together,
I have a question regarding process-control. I want to write a perl script
which must not running in more than one process in the same time. The script
creates a directory copys a zip-file in it, unpack it and reads every file in
this package. However, the files must not get opened by another process.
How can I make sure, that my perl-scipt runs only in one process, or eaysier,
is there a function "flock" which blocks a whole directory and not only a
single file?
Step 1, when your script launches, have it create a file in some convenient directory. Maybe call it "LOCK", or something similar. It doesn't need a thing in it, just make a file.
Step 2, if the file already exists when your script launches, have it abort with some notification.
Note: You can, and should, combine the check for the file and creation of it with Perl's sysopen() built-in.
You can also go farther, say writing the creating processes' PID to the file and using that as a secondary check to make sure the process is actually running. This is starting to be work though of super questionable value for a simple script. Use the proper amount of paranoia for your particular case.
Step 3, ensure that your script unlink()s the file on exit. Perl's END { } blocks are ideal for this.
Hope that helps.
James
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