tail -f /dev/null » while

Process A File Line By Line In A Script

Uncle Jubba — Thu, 15 Jan 2009 18:54:32 +0000

There are multiple ways to skin this cat. For now one of the simplest.

#!/bin/sh

while read LINE
do
...DO SOME STUFF WITH THE ${LINE}...
done 
Replace “somefile.txt” with the file you want to process.
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Spawning Sub-Shells

Uncle Jubba — Thu, 18 Dec 2008 21:59:56 +0000

Creating sub-shells in bash is simple: just put the commands to be run in the sub-shell inside parentheses. This causes bash to start the commands as a separate process. This group of commands essentially acts like a separate script file, their input/output can be collectively redirected and/or they can be executed in the background by following the closing parenthesis with an ampersand.

#!/bin/bash

server_cmd=server
pid_file=$(basename $server_cmd .sh).pid
log_file=$(basename $server_cmd .sh).log

(
    echo "Starting server"
    echo "Doing some init work"
    $server_cmd   # server becomes a daemon

    while true
    do
        if [[ -f $pid_file ]]; then
            sleep 15
        else
            break
        fi
    done
    mail -s "Server exitted" joe@example.com <<&1 >> $log_file &

echo "Server started"
quote and example via LinuxJournal
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Increase Loadaverage

Uncle Jubba — Sat, 06 Dec 2008 17:03:37 +0000

Increase the load average on a machine for testing.

while true; do w & w & w & w; done
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