Jasmine
Administrator
Jan 26, 2001, 10:04 AM
Post #1 of 1
(2888 views)
|
|
How can I manipulate fixed-record-length files?
|
Can't Post
|
|
(From the Perl FAQ)
How can I manipulate fixed-record-length files?
The most efficient way is using pack() and unpack(). This is faster than using substr() when take many, many strings. It is slower for just a few.
Here is a sample chunk of code to break up and put back together again some fixed-format input lines, in this case from the output of a normal, Berkeley-style ps: # sample input line:
# 15158 p5 T 0:00 perl /home/tchrist/scripts/now-what
$PS_T = 'A6 A4 A7 A5 A*';
open(PS, "ps|");
print scalar <PS>;
while (<PS>) {
($pid, $tt, $stat, $time, $command) = unpack($PS_T, $_);
for $var (qw!pid tt stat time command!) {
print "$var: <$$var>\n";
}
print 'line=', pack($PS_T, $pid, $tt, $stat, $time, $command),
"\n";
}
|
MAIN
SEARCH
WHO'S 
LOG 