Comment lines in the Bourne shell

[Andy Merritt]

> I've noticed that on my system (2.8BSD) the Bourne shell
> comment character doesn't do what I expected.  The shell
> still looks at some characters on the line, even though
> the line is commented out.  For example, the comment
> 
> : to use this file type <name> | lpr
> 
> produces a message referring to the pipe, even though the whole
> line is commented out.  What am I missing?
> 
> -- 
> 	Jeff Percival ...!uwvax!uwmacc!jwp

According to the SysV documentation I have, ':' is a special command for which
the manual says
:	no effect; the command does nothing. A zero exit code is returned.

This implies that the effect is not to ignore the rest of the line as you  
expected, but to take as arguments anything up to a normal terminator and
then do nothing with them. The | is met in this case, and nothing is in the
input for the lpr.

I guess this must be what is happening on the 2.8BSD system also.

		Andy
    /^^^\
   ( o o )
--w---U---w--	  UUCP: ...!ukc!stc!iclbra!apm
"Wot, no news?"   MAIL: Andrew Merritt, ICL, Lovelace Rd, Bracknell, Berkshire