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Replace a specific column with a specific value

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# 1  
Old 09-01-2014
Replace a specific column with a specific value
Hi,

I am looking to replacing value of a specific column of /etc/pam.d/system-auth file. My file looks like this

Code:
password sufficient pam_unix.so md5 shadow nullok try_first_pass use_authtok

expected result

Code:
password sufficient pam_unix.so md5 shadow nullok try_first_pass use_authtok remeber=10

Any suggestion would be appreciated...

Regards,
Litu
# 2  
Old 09-01-2014
Hi Litu,

Following may help you in same.

Code:
echo "password sufficient pam_unix.so md5 shadow nullok try_first_pass use_authtok" | awk '$(NF+1)="remeber=10"'
OR
awk '$(NF+1)="remeber=10"' filename
OR
echo "password sufficient pam_unix.so md5 shadow nullok try_first_pass use_authtok" | awk '$(NF+1)=s1' s1="remeber=10"

Output will be as follows.

Code:
password sufficient pam_unix.so md5 shadow nullok try_first_pass use_authtok remeber=101


Thanks,
R. Singh
Last edited by RavinderSingh13; 09-01-2014 at 11:39 AM.. Reason: Added one more solution
# 3  
Old 09-01-2014
this file may contain other entries as well. does this logic will work ?

also would you pls explain this command.
# 4  
Old 09-01-2014
Litu,

This solution will work when you need to add variable at the last of the line. If any conditions are there for the variable to be added please let us know with full description, but if you need to add variable at last solution will work. Explaination of the solution is as follows.
Code:
echo "password sufficient pam_unix.so md5 shadow nullok try_first_pass use_authtok" | awk '$(NF+1)="remeber=10" 1'

$(NF+1) means I am adding one more field at last of the line as a line will have acually NF number of fields only, then I am giving 1 which means I am making condition part set to true so be default print operation will take place. Please refer man awk also for same, will be helpful for you.

EDIT: Please use the following solution for same as above solution will not give requested output, thanks Franklin for pointing it out.

Code:
awk '$(NF+1)="remeber=10"' filename

Thanks,
R. Singh
Last edited by RavinderSingh13; 09-01-2014 at 11:44 AM.. Reason: Adding correct solution to the thread
# 5  
Old 09-01-2014
Quote:
Originally Posted by RavinderSingh13
Litu,

This solution will work when you need to add variable at the last of the line. If any conditions are there for the variable to be added please let us know with full description, but if you need to add variable at last solution will work. Explaination of the solution is as follows.
Code:
echo "password sufficient pam_unix.so md5 shadow nullok try_first_pass use_authtok" | awk '$(NF+1)="remeber=10" 1'

$(NF+1) means I am adding one more field at last of the line as a line will have acually NF number of fields only, then I am giving 1 which means I am making condition part set to true so be default print operation will take place. Please refer man awk also for same, will be helpful for you.


Thanks,
R. Singh
Code:
awk '$(NF+1)="remember=10" 1'

doesn't give the correct output.

You should surround the command with braces:
Code:
awk '{$(NF+1)="remember=10"}1'

or
Code:
awk '$(NF+1)="remember=10"'

If you add a field with a value which is not empty, awk considers the action as true, so a 1 is superfluous.
# 6  
Old 09-01-2014
Thanks Franklin52 for letting us know, I will remove that code but other code
Code:
echo "password sufficient pam_unix.so md5 shadow nullok try_first_pass use_authtok" | awk '$(NF+1)=s1' s1="remeber=10"

is working fine.


Thanks,
R. Singh
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