Re: [FWP] TMTOWTDI

[Peter Scott <Peter@PSDT.com>]

At 11:17 AM 6/26/99 -0700, Vicki Brown wrote:
># Which way would you pick?  Why

Why, it depends, of course :-)

># Problem
># You have an external command to run from perl; the command returns a
># large chunk of newline separated data which you want to process, line
># per line.
>#
># Would you:
>#
>#    1) write the returned data to a file, open it, and loop through the
lines

Unlikely, but if I was in an environment where fault tolerance and
checkpoint/restart or having an audit trail in the event of a crash was
important, I might do this.

>#    2) do an open with a pipe when you call the external command and attach
>#       the data to the filehandle, then iterate over <HANDLE>
>
>         open(HANDLE, "command |")
>         ...
>         while (<HANDLE>) {

The best way in general, unless the command is going to output more data
than my input loop is going to handle in time and I have some concern about
how long I want the command process to stick around.  This would not do for
real-time monitoring, for instance, if command was returning data faster
than I could or wanted to process it.

>#    3) stuff the returned data into a large string variable, split it, and
>#       foreach across the result
>
>          $result = `command`;
>          @lines = split(/\n/, $result);
>          foreach $line (@lines) {

What I usually do when I know the command is going to output a known and
not large amount of data is just

	foreach (`command`) {

rather than create the extra variables.  I make sure that command always
ends in 2>&1.

>#    4) none of the above (in which case what would you do?)

Send data in morse code by going into tight loops in the child and watching
for jumps in the system clock in the parent :-)


Peter Scott
Pacific Systems Design Technologies


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