sed help needed

avijitp · 11-19-2007, 03:40 AM

I want to remove USERID from my /etc/xinetd.conf in 300 servers and for that I want to use "sed" through a script.
The file

Code:

defaults
{
        instances               = 60
        log_type                = SYSLOG authpriv
        log_on_success          = PID HOST USERID EXIT DURATION
        log_on_failure          = HOST USERID ATTEMPT
        cps                     = 25 30
}

includedir /etc/xinetd.d

Should look like ...

Code:

defaults
{
        instances               = 60
        log_type                = SYSLOG authpriv
        log_on_success          = PID HOST EXIT DURATION
        log_on_failure          = HOST ATTEMPT
        cps                     = 25 30
}

includedir /etc/xinetd.d

I used
sed 's/USERID //' /etc/xinetd.conf

But it is showing me correct output in the screen, but it is not writing to the file.

acid_kewpie · 11-19-2007, 03:59 AM

it won't write it to the file, it's not meant to. you would save that as a temp file and replace it afterwards with sed. yo could use ex instead to directly modify the file rather than editing a stream on the fly.

jschiwal · 11-19-2007, 04:03 AM

GNU sed has an inplace option to perform the edit on the file directly.
sed -i '/log_on_success/s/USERID //' /etc/xinetd.conf

acid_kewpie · 11-19-2007, 04:14 AM

ah, duly noted...

avijitp · 11-19-2007, 04:16 AM

jschiwal,

You are the One!!

I just did the same with
sed -i 's/USERID //' /etc/xinetd.conf

and it does what I wanted to to. e.i, remove the USERID from muliple lines too.

Thanks a lot.

pppaaarrrkkk · 11-19-2007, 08:14 AM

Quote:

Originally Posted by acid_kewpie

it won't write it to the file, it's not meant to. you would save that as a temp file and replace it afterwards with sed. yo could use ex instead to directly modify the file rather than editing a stream on the fly.

Does this mean that if you know what you want to replace, there is a utility 'ex' which is better than 'sed' ?

acid_kewpie · 11-19-2007, 08:22 AM

well ex is a command line version of vi, which you *should* know intimately already. the -i option clearly does the job too though, so it's down to user comfort only...

pixellany · 11-19-2007, 08:24 AM

Quote:

Originally Posted by pppaaarrrkkk

Does this mean that if you know what you want to replace, there is a utility 'ex' which is better than 'sed' ?

"ex" invokes a special mode of the VIM editor. I don't know VIM, but I assume it must have a search and replace function. (Search and replace is of course one of the main things SED does).

"better"? I would say SED is probably more powerful---but an editor might be easier to use

acid_kewpie · 11-19-2007, 08:33 AM

you don't know vi? shame on you, i thought you were better than that

I actually took a long time to try vi, stuck firm with pico / nano for about 5 years, but vi clearly is totally awesome.