[NTLUG:Discuss] sed question
Burton M. Strauss III
Burton_Strauss at comcast.net
Wed Apr 7 08:40:54 CDT 2004
Have you considered Awk?
BEGIN {
if(ARGC != 3) {
print "usage: awk -f script.awk ntp1 ntp2 <oldconf >newconf"
exit(0);
}
ntp2=ARGV[2]
ARGV[2]=""
ntp1=ARGV[1]
ARGV[1]=""
}
# Retain server 127.xxxx lines
/^server *127/ { print $0; next }
# Drop all other server lines
/^server/ { next }
# Echo anything else
{ print $0 }
END {
# Now create our new server lines
print "server " ntp1
print "server " ntp2
}
(I haven't actually tried the code, but it or something like it should work)
-----Burton
> -----Original Message-----
> From: discuss-bounces at ntlug.org [mailto:discuss-bounces at ntlug.org]On
> Behalf Of Ralph Green, Jr
> Sent: Wednesday, April 07, 2004 2:47 AM
> To: NTLUG Discussion List
> Subject: [NTLUG:Discuss] sed question
>
>
> Howdy,
> sed is one of those neat tools I always thought I should know, but
> never managed to use. I have a good application for it now and there is
> one thing I have not figured out. If you have a suggestion, please let
> me know. If you think this is the wrong tool, I'll listen to that. I
> want to do this in an efficient way.
>
> The problem is this. I have a web page written in PHP. It allows the
> user to specify two NTP servers to use to keep the machine
> synchronized. When a user changes the servers on the web page, I need
> to update the /etc/ntp.conf file and then restart the NTP service. My
> only probleem is updating the config file. The two lines that need to
> be changed of /etc/ntp.conf are shown here between the dashed lines:
> - - - - - - - - - - - - - - - - - - -
> server ntppub.tamu.edu
> server tick.usno.navy.mil
> - - - - - - - - - - - - - - - - - - -
> There are a couple of things to keep in mind.
> 1. There is another line in the file that starts with server. It says
> server 127.127.1.0 or some such. It needs to be left unchanged.
> 2. While I will know what the two server lines said the last time I
> updated the file because I have database entries for them, the user
> could have made manual changes. The script need to work in any case.
>
> I know one way to solve this would be to issue a command like
> sed '/server[ \t][^0-9]'/d <ntp.conf >ntp.new
> This would delete any active server lines and then I could append my
> new ones to the bottom of the file. I'll go with this plan if I have
> too,It os not pretty, but it is functional.
>
> It looks like there might be a way to tell sed to go to the first
> matching line and then insert text(my new server lines) and then delete
> the matching lines. This has the advantage that the server lines appear
> in their normal place in the file, below the appropriate comment block.
> But, I have not gotten this to work.
>
> Do you understand what I am trying to accomplish? Can you offer a
> suggestion?
> Thanks,
> Ralph
>
>
>
>
>
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