Re: How to use sed to remove a line from a cron file and also remove all commented lines directly above it

On 10Jul2012 13:57, [email protected] <[email protected]> wrote:
| From: "Jim Schneider" <[email protected]> 
| > [...] I realize I'm cheating here but 
| > crontab -l | grep -p -v 'Purge tables' > new.crontab 
| > 
| > will do the trick.  The '-p' flag treats blocks of text separated by
| > blank lines as a single unit.  The '-v' flag excludes that block of text.
| > After verifying new.crontab, move it into place. 
| > 
| > I realize I'm suggesting unix commands in place of sed and don't intend to offend this group. 
| 
| Thanks, I learned something from that answer. 

But again, PLEASE, reply inline and trim redundant text. It makes things
MUCH easier for the readers.

| However, when I sent the original email, there were no blank lines in the text. 
| Those were inserted by something between my Comcast account and the users group. 
| I think cron doesn't allow blank lines. 

It does. Please read "man 5 crontab". An excerpt:

  Blank lines and leading spaces and tabs are ignored.  Lines whose first
  non-space  character is a pound-sign (#) are comments, and are ignored. 

| Also, I am looking to remove the block of commented lines, if any, that are directly 
| above the specified pattern.  In the example I gave it begins with "# Purge" but in general 
| it could be any commented line (or no line at all). 

I would also be uncomfortable about grep's -p option here: it only takes
an accidental (manual) removal of the blank lines between clauses to
bundle two command lines in the one paragraph, and then badness ensues.

Cheers,
-- 
Cameron Simpson <[email protected]>

>>>How do you blip the throttle and wave? Do you blip it real high, then wave
>>>before the revs drop back?
>>Blip = right hand; Wave = left hand.  Do both simultaneously.  QED.
>Doesnt this make the bike lurch forward thru the intersection?
Not if the disk lock is in place...
        - Dean Woodward <[email protected]>