dos to unix CR/LF conversion?

[Henry Spencer]

On Sat, 8 Nov 2003, Max Blanco wrote:
> you were right.  My mac/ie5 converted linefeeds to ^m, instead of \r.
> I can't see straight anymore between '\n', '\r', "^M", "^L", C, perl, tr, 
> unix, dos, mac, dog, cat.  Arrgh.  

Let's get this one sorted out once and for all...

Unix end-of-line is ASCII LF = linefeed = newline = \n = \012 = ^J.  (This
actually follows the ASCII standard, which says that if one character is
used for newline, it shall be LF.)

Mac end-of-line is ASCII CR = carriage return = \r = \015 = ^M.  (This is
just wrong, a stupid violation of standards, but it's a bit late to fix
Apple's botch.)

DOS/Windows end-of-line is ASCII CR followed by ASCII LF.  (This also
follows the ASCII standard, which by default separates CR "go back to left
margin" from LF "go down to next line".  However, with two characters, you
have all sorts of fun questions about what happens if they show up in the
wrong order, or if only one of them shows up.  Unix made the right choice
by using a single character.)

^L is formfeed, and ^R is an obscure device-control character, and neither
of those is involved at all. 

Converting Unix to Mac or vice-versa is easy on most modern systems:

	tr '\n' '\r' <input >output	# Unix to Mac
	tr '\r' '\n' <input >output	# Mac to Unix

(On old systems, it may be necessary to spell \n as \012 and \r as \015.)
This just transforms one character into the other.

Converting DOS to Unix is likewise easy:

	tr -d '\r' <input >output	# DOS to Unix

This deletes the silly CRs, leaving the LFs which are already in the 
right places.

Going *to* DOS is a little harder, because it requires inserting the
missing characters, which "tr" can't do.  You could do it with "sed", but
that's a little awkward because of the lack of good escape conventions for
the unprintable characters.  So let's use awk instead: 

	awk '{ print $0 "\r" }' <input >output		# Unix to DOS

                                                          Henry Spencer
                                                       henry-lqW1N6Cllo0sV2N9l4h3zg at public.gmane.org

--
The Toronto Linux Users Group.      Meetings: http://tlug.ss.org
TLUG requests: Linux topics, No HTML, wrap text below 80 columns
How to UNSUBSCRIBE: http://tlug.ss.org/subscribe.shtml