Beefy Boxes and Bandwidth Generously Provided by pair Networks
more useful options
 
PerlMonks  

Re: Blank data file

by kvale (Monsignor)
on Jul 09, 2002 at 21:15 UTC ( #180611=note: print w/replies, xml ) Need Help??


in reply to Blank data file

I have seen this problem before, due to multiple processes trying to read and write files simulataneously. Here is a more cautious style of locking using flock that hasn't let me down yet (probably adapted from the Cookbook, I can't remember):
# reading open NEWSRC, "< $newsgroup_file" or die "Could not open newsgroup file $newsgroup_file\n"; unless (flock NEWSRC, LOCK_SH | LOCK_NB) { print "Contention: cannot get a shared lock the file, blocking ($!) +...\n"; unless (flock NEWSRC, LOCK_SH) { die "ERROR: cannot get a shared file lock on $newsgroup_file: $! +\n"; } } print "Initial newsrc read lock granted\n"; my @news_lines = <NEWSRC>; close NEWSRC; # writing open NEWSRC, "+< $newsgroup_file" or die "Could not open newsgroup file $newsgroup_file\n"; unless (flock NEWSRC, LOCK_EX | LOCK_NB) { print "$group ($$): Contention: cannot get an exclusive lock the fi +le,\n blocking ($!) ...\n"; unless (flock NEWSRC, LOCK_EX) { die "$group ($$): ERROR: cannot get an exclusive file lock on $n +ewsgroup_file: ($!)\n"; } } print "$group ($$): Write lock granted\n"; print NEWSRC @news_lines or die "Disk full\n"; close NEWSRC;
-Mark

Log In?
Username:
Password:

What's my password?
Create A New User
Node Status?
node history
Node Type: note [id://180611]
help
Chatterbox?
[Corion]: A good daypart!
Corion feels slightly bad for initiating a discussion yesterday and then running away. I guess I should write that up as a meditation or SoPW
[Corion]: Not the "running away" part but the question+ discussion about IO-less HTTP modules
[Corion]: (or how/where to patch AnyEvent::HTTP or LWP::UserAgent to take control of both the callstack and the data transfer)

How do I use this? | Other CB clients
Other Users?
Others rifling through the Monastery: (5)
As of 2016-12-08 09:03 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?
    On a regular basis, I'm most likely to spy upon:













    Results (137 votes). Check out past polls.