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
-
Are you posting in the right place? Check out Where do I post X? to know for sure.
-
Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
<code> <a> <b> <big>
<blockquote> <br /> <dd>
<dl> <dt> <em> <font>
<h1> <h2> <h3> <h4>
<h5> <h6> <hr /> <i>
<li> <nbsp> <ol> <p>
<small> <strike> <strong>
<sub> <sup> <table>
<td> <th> <tr> <tt>
<u> <ul>
-
Snippets of code should be wrapped in
<code> tags not
<pre> tags. In fact, <pre>
tags should generally be avoided. If they must
be used, extreme care should be
taken to ensure that their contents do not
have long lines (<70 chars), in order to prevent
horizontal scrolling (and possible janitor
intervention).
-
Want more info? How to link
or How to display code and escape characters
are good places to start.
|