Help with strings in Bourne shell

[Stephen J. Friedl]

In article <1493 at vsedev.VSE.COM>, logan at vsedev.VSE.COM (James Logan III) writes:
> 
> BTW, you can also read from a specific file by redirecting the
> input to the read command like this:
> 
> 	while read DEFINITION < inputfile; do
> 		echo "$DEFINITION";
> 		# other stuff
> 	done;

This is a common mistake.  The redirection applies to only the
read command, and every time the while hits the read, the input
file is opened anew and the same first line is read over and
over (and the while never terminates).  Try:

	while read line < /etc/passwd ; do
		echo $line
	done

and you'll learn your encrypted root password quite well.

The {Bou,Ko}rn shells support piping and redirection into and
out of control flow, so things like:

	while read foo ; do
		stuff here
	done < inputfile
or
	while condition ; do
		stuff here
	done > outputfile
or
	grep stuff file | while read line ; do .... ; done

all do things that make sense.

     Steve

-- 
Stephen J. Friedl / V-Systems, Inc. / Santa Ana, CA / +1 714 545 6442 
3B2-kind-of-guy   / friedl at vsi.com  / {attmail, uunet, etc}!vsi!friedl

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