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Need bash script to use a sed command as a variable

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# 1  
Old 08-21-2019
Need bash script to use a sed command as a variable

I need to be able to use a sed command as a variable in a bash script. I have the sed command that almost works the way I want it. the command is

sed -n '/inet/,/}/p' config.boot

This gets me this result:

I need to get the IP address into a variable so I can use it. How do I use sed to strip off the inet and the }.

How does the command need to be changed to get this to work?


Last edited by Peasant; 08-22-2019 at 12:20 AM.. Reason: Code tags. Use them please.
# 2  
Old 08-21-2019
ip=$(sed -n '/inet/,/}/{/inet/{s/inet *//;{p;q}}}' config.boot)

Last edited by rdrtx1; 02-18-2020 at 09:28 PM..
# 3  
Old 08-21-2019
Thank you ! That works perfectly
# 4  
Old 08-21-2019
Could be simplified as you want to quit after the first ip encountered:
ip=$(sed -n '/inet */ {s///; p; q}' file)

This User Gave Thanks to RudiC For This Post:
# 5  
Old 08-22-2019
Note that with standard sed (non-GNU) there needs to be a ; before the trailing }:
ip=$(sed -n '/inet */{s///p;q;}' config.boot)

or we can avoid the braces by using negation style:
ip=$(sed '/inet */!d; s///; q' config.boot)

Alternatively we can avoid the sub shell / external command altogether with just standard shell:
until [ "$inet" = inet ]; do
  read inet ip
done < config.boot

Note also that these are all naive approaches without knowing what the format of config.boot looks like. Also, if the are more inet configs in the same file, these will only pick the first one indiscriminately.

Last edited by Scrutinizer; 08-22-2019 at 04:16 AM..
# 6  
Old 08-22-2019
As a professional you should expect the unexpected.
What happens if the read fails or the "inet" is not found?
The following ends the loop if the read fails.
  read inet ip &&
  [ "$inet" != inet ]
done < config.boot

This User Gave Thanks to MadeInGermany For This Post:
# 7  
Old 08-22-2019
Yes that was indeed not a good approach. Also a good thing you pointed out that the shell approach only gives a proper answer if inet is present in the file. But this would still not solve that issue.

This may be more appropriate:

while read key value; do
  if [ "$key" = inet ]; then
done < config.boot

Last edited by Scrutinizer; 08-22-2019 at 05:39 AM..

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