Why shouldn't ^J (linefeed) be used as a command in an application?

[Doug Gwyn]

In article <4404 at sfsup.UUCP> gill at sfsup.UUCP (Timothy D. Gill) writes:
>we want to change it because of a conflict with the use of ^Z for 
>the SUSPEND line discipline character for BSD-style job control.  

Note that you can disable or change that special character in the
new-tty handler, permitting its continued use in your application.

>Our only choices are ^C and ^J because all other control characters 
>are used by the tool already.

Ouch.  What are you going to do when you need to add another
function?  This might be a good time to figure that out.

>What are the historical or cultural reasons that ^J is not used in UNIX
>tools?  Is there a strong reason not to use it now?

^J (ASCII LF) is, of course, the character UNIX uses in text files
and streams to denote "new line".  Depending on the terminal handler
modes, a received CR may be mapped into LF (also there are some
options concerning how CR and LF are echoed).

Some terminals don't have CR, just NL (same code as LF).