09-04-2008
Quote:
Originally Posted by
DILEEP410
fine.But my question is if i go with your way of letting the script sleep for 1800 seconds, the entire code remains in memory for 30 minutes,right?
But if i reschedule it the memory will be free for 30 minutes.
Since the server is supposed to run a lot of cron jobs may be simultaneously,is better to think from memory perspective.
Please correct me if am wrong,because am not an expert in this!
It's an interesting and valid point, as it's an interpreted script, you'd have the perl engine + any variables etc declared sitting about in memory wheras an 'at' invocation would clear out and leave the memory free until it's needed. I'm of the same school of thought that if we don't need to use RAM, we shouldn't.
But, there are some things to consider:
- Your average perl binary is pretty small as far as memory footprints go
- Modern unix systems typically don't have the kind of memory issues we used to have, physical chip ram is still precious but swap space on disk is usually rather copious.
- CPU time is still precious, to start a new perl interpreter up is considerably more expensive on CPU than just running a sleep (to all intents and purposes, 0% cpu used) for 30 mins.
- The operational risk _could_ be greater using 'at', this really depends on how the job works though. If you run this thing and it's waiting on some condition to complete before it carries on, could someone make the mistake of seeing it's finished running and thinking that means it's done? They might either run it again (resulting in two 'at' jobs scheduled) or assume it's fully complete.
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LEARN ABOUT NETBSD
script
SCRIPT(1) BSD General Commands Manual SCRIPT(1)
NAME
script -- make typescript of terminal session
SYNOPSIS
script [-adfpqr] [-c command] [file]
DESCRIPTION
script makes a typescript of everything printed on your terminal. It is useful for students who need a hardcopy record of an interactive
session as proof of an assignment, as the typescript file can be printed out later with lpr(1).
If the argument file is given, script saves all dialogue in file. If no file name is given, the typescript is saved in the file typescript.
Option:
-a Append the output to file or typescript, retaining the prior contents.
-c command
Run the named command instead of the shell. Useful for capturing the output of a program that behaves differently when associated
with a tty.
-d When playing back a session with the -p flag, don't sleep between records when playing back a timestamped session.
-f Flush output after each write. This is useful for watching the script output in real time.
-p Play back a session recorded with the -r flag in real time.
-q Be quiet, and don't output started and ended lines.
-r Record a session with input, output, and timestamping.
The script ends when the forked shell exits (a control-D to exit the Bourne shell (sh(1)), and exit, logout or control-d (if ignoreeof is not
set) for the C-shell, csh(1)).
Certain interactive commands, such as vi(1), create garbage in the typescript file. script works best with commands that do not manipulate
the screen, the results are meant to emulate a hardcopy terminal.
ENVIRONMENT
The following environment variable is used by script:
SHELL If the variable SHELL exists, the shell forked by script will be that shell. If SHELL is not set, the Bourne shell is assumed. (Most
shells set this variable automatically).
SEE ALSO
csh(1) (for the history mechanism).
HISTORY
The script command appeared in 3.0BSD.
BUGS
script places everything in the log file, including linefeeds and backspaces. This is not what the naive user expects.
BSD
October 17, 2009 BSD