On Sun, 2008-04-06 at 22:36 -0400, Richard Lee wrote:
> I am trying to open a big file and go through line by line while
> limiting the resource on the system.
> What is the best way to do it?
>
> Does below read the entire file and store them in memory(not good if
> that's the case)..
>
> open(SOURCE, "/tmp/file") || die "not there: $!\n";
> while (<SOURCE>) {
> ## do something
> }
The above code will read the file one line at a time. It is recommended
that you use the three-argument open statement. (See `perldoc -f
open`).
open( SOURCE, '<', "/tmp/file" ) || die "cannot open /tmp/file: $!\n";
while (<SOURCE>) {
# do something
}
>
> sometime ago I saw somewhere it had something like below which look like
> it was reading them and going through line by line without storing them
> all in memory.
> I just cannot remember the syntax exactly.
>
> open(SOURCE, " /tmp/file |") || die "not there: $!\n";
> while (<>) {
> ## do something
>
> }
This syntax is is used for reading the output of another command. It is
not recommended because your program would not be ****table across
operating systems. But sometimes you have no choice.
open( SOURCE, '-|', "command" ) || die "cannot pipe from command: $!\n";
while (<SOURCE>) {
# do something
}
Also see `perldoc IPC::Open2` and `perldoc IPC::Open3`
--
Just my 0.00000002 million dollars worth,
Shawn
99% of you are just big dumb apes!
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