Help about sed

[Gandalf]

Hello,

I'm trying to change a file which has the below line in it, i want to comment it


30 3 * * * /var/www/vhcs2/engine/tools/vhcs2-httpd-logs-mngr &>/var/log/vhcs2/vhcs2-httpd-logs-mngr.log


so i've tried to do


sed -i -e "s/\(.*vhcs2-httpd-logs-mngr.*\)/#\1/g"

it will succeed except that running it again will add another comment
can anyone tell me how can i Add # just before the 30 because i need it also to do the reverse operation, uncommenting it

Thanks

[coredump]

Sounds like you need to make 'sed' ignore the line when it's already commented out. One way to do that would be to add something to the pattern that you're matching for, so that the initial hash will make the match fail. How about:


sed -i -e "s/\([^#].*vhcs2-httpd-logs-mngr.*\)/#\1/g"

or even:


sed -i -e "s/\([^#]*vhcs2-httpd-logs-mngr.*\)/#\1/g"

The second one will fail to match if a hash occurs anywhere in the line before the string you're looking for. I'm using the square brackets to specify a character class (i.e. any one character from the range specified will match) and then negating it with the up-arrow so that only the hash will fail to match.

Do let us know if that works!

[Gandalf]

Nope :(

both of them still add # again and over again whenever the process started again :(

[coredump]

Oh crap, I realised as soon as you said that why it won't work -- now why couldn't I have realised before I posted it! All that the [^#] stuff does is make the pattern match one character later, after the '#'. Try adding an uparrow to make it an anchored match:


sed -i -e "s/^\([^#].*vhcs2-httpd-logs-mngr.*\)/#\1/g"

The uparrow is special when it's the first character of a pattern, and it matches the beginning of a line.

Hope that's better...

[jerome bettis]

awk is way easier to use then sed if you know C syntax

awk :cool:

[Gandalf]

@coredump, Thank you that worked like a charm, how about removing it now?
this worked for me


sed -i -e "s/^#\([^#].*vhcs2-httpd-logs-mngr.*\)/\1/g"
but is it good one?

@jerome bettis: can you point me to a guide or tutorial please?