Shell tips and tricks

[VirginSnow at vfemail.net]

> Date: Wed, 31 Oct 2007 13:35:07 -0400 (EDT)
> From: "Steven W. Orr" <steveo at syslang.net>

> Ok. In that vein, I have two areas that I personally find interesting.
> 
> 1. The area of *proper* bash initialization. How people set up their init 
> files is an area of universal shame.
> 
> 2. How to write scripts that do what the shell is capable of with (more) 
> minimal callouts to external programs. This is more than turning things 
> like cat fn | grep into grep < fn. Good things happen when people get more 
> comfortabler with looking constructs, signals, advanced descriptor 
> management, to name just a few.
> 
> Just for starters, one things I see on a pretty regular basis is this 
> erroneous construct:
> 
> foo=44
> p1 | while read line
> do
>     dosomething
>     foo=$((foo + 1))
> done
> echo "foo = $foo"

Did you intentionally leave the "$" out of "$foo + 1"?

Things I think may be worth studying:

 (1) Managing file descriptors on the command line.  What's already
     open?  What's open read-only, read-write, etc.?

 (3) Here-documents and here-strings.  How is this here-document going
     to be munged?  (i.e., What the heck is going to be substituted
     in my hear-document?)

 (4) All that ${%%:-//} funny variable parsing stuff.  (Good
     replacement for some calls to cut/sed.)

 (5) Variable scope (see above riddle).

 (5) Using /dev/{tcp,udp}.  Save calls to netcat.

 (7) Shell options?  What are those?