Re: sed file processing?

This action is happening on a free-bsd system and I don't know if eol 
markers are put on ends of lines in native format.  I am using 
spamassassin and sending spam to probably-spam for further action.  
Aside from what the program learns or fails to learn, the script 
searches down through probably-spam and finds all of the From: lines and 
saves those to a file called rf.  What I'm going to do with sed is to do 
a command like sed -e "%s/^/blacklist-/ rf <cr> that should tack 
blacklist- onto the beginning of every line in rf.  Once that's done, 
~/.spamassassin/user_prefs needs a little concatenation of the file 
called rf.  Once that's done I delete the file called rf and a .logout 
script runs sa-learn --spam then deletes all email in probably-spam.  
Last time I checked, 794 unique entries in user_prefs that are 
blacklisted.  This has started in October 2013 so that will give you an 
idea as to the spam volume around here.  I figure the more I can 
automate the fewer mistakes happen and sed is golden in terms of these 
capabilities!  I could probably have automated more in this work flow 
with sed than was done, but I figured at least this operation might have 
been something sed could handle well and it appears sed will do it 
better than I expected.

On Fri, 14 Feb 2014, [email protected] wrote:

> That was a great question. 
> 
> As in previous response, if the file is totally empty, sed tries to read the first line, fails, and exits.
> 
> If the file has one line, but no EOL marker, sed reads the line, but somehow figures out NOT to an EOL marker when it outputs the pattern space. 
> 
> Here is the normal case with EOL marker:
> 
> $ echo  "X" | sed "s/X/Y/"
> Y
> $
> 
> Here is the case with EOL marker missing:
> 
> $ echo -n "X" | sed "s/X/Y/"
> Y$
> 
> Are you wanting sed to take no action if no EOL marker on single line?
> 
> Daniel
>  
> ---In [email protected], <dave_br@...> wrote:
> 
>  On Fri, 14 Feb 2014 06:05:12 -0500 (EST), Jude DaShiell
>  <jdashiel@... mailto:jdashiel@...> wrote:
>  
>  > Is it within sed's logical capacity to check a file and only do a command 
>  > on that file if it has at least one line of text in it? For what I'm 
>  > trying to do with a script, if the file has zero lines it should not have 
>  > anything done to it.
>  
>  If a file has zero lines sed can't do anything on it anyway, since by
>  definition sed works on input lines.
>  
>  $ touch a
>  $ sed 's/^/foobar/' a
>  $
>  
>  Pleae note that a file that is NOT 0 bytes in size is neither an empty file
>  nor one with no lines of text.
>  
>  -- 
>  D.
> 
> 

jude <[email protected]>