The Real Linux World

Mark Sargent powderkeg at snow.email.ne.jp
Thu Apr 28 06:26:36 UTC 2005


Hi All,

tasty heading..? Ok, whilst I enjoy spinning people with the following, 
"Nah, mate, don't use Windows", which usually gets the suprised 
response, "oh, what do u use, MAC".  Of which I reply, "ah, u all know 
what I reply with". BUT, I feel I'm not really a Linux person unless 
I've mastered, Shell Programming, where I believe the real power of 
Linux World exists. Anyway, enough dribble, and on to my question of the 
day. I'm following this tut,

http://www.tldp.org/LDP/abs/html/sha-bang.html

and in the code on that page, there is are variables, $1 and $LINES. Um, 
what are they..?

if [ -n "$1" ]
# Test if command line argument present (non-empty).
then
  lines=$1
else  
  lines=$LINES # Default, if not specified on command line.
fi  

and then further down, I see this use of one of them,

tail -$lines messages > mesg.temp # Saves last section of message log file.
mv mesg.temp messages             # Becomes new log directory.


Can anyone explain this in plain English.? I understand that a portion of messages is being written to mesg.temp,
and that the rest is deleted. Just don't get where $1 and $LINES is being generated from. Cheers.

Mark Sargent.







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