UNIX for Dummies Questions & Answers

Hi,

I have a file named as 'Todays.prm'. This file has a date on a second line. I want to replace the date to todays date whenever this command is executed.

My File looks as below:

Code:

[GLOBAL]
$$TODAYSDATE=2014-06-24-18.45.50

When this command will be run tomorrow the data in the file shoudl look like

Code:

[GLOBAL]
$$TODAYSDATE=2014-06-25-18.45.50

The variable $$TODAYSDATE will always be on second line of the file. Could you please help me out with this. I tried using SED/AWK coomand but nothing seemed to be working.

-Vrushank Patel

Welcome to forums,

Try [untested]

Code:

$ sed "2s/=.*/=$(date +"%Y-%m-%d-%H.%M.%S" )/" file

Code:

$ awk 'FNR==2{sub(/=.*/,strftime("=%Y-%m-%d-%H.%M.%S",systime()))}1' file

Thanks Akshay. When I run this cmd it displays me the content of file with updated date but when I try to open up File its still showing the old date.Its not updating the file. Is this because the owner of the file is someone else and I am trying to 'sed' it with different ID?

-Vrushank Patel

use this sed -i.bak "2s/=.*/=$(date +"%Y-%m-%d-%H.%M.%S" )/" file

Code:

-i[SUFFIX], --in-place[=SUFFIX]
   edit files in place (makes backup if extension supplied)

The common way is to redirect the output output to a new file.
some_cmd file > newfile

If the output is correct then you can replace the old file with the new file. If that file is important, you can chose to make an extra backup of the original file first:

Code:

mv file file.backup
mv newfile file

You can also do something like this:

Code:

some_cmd file > newfile && mv newfile file

That way the the mv operation is only performed if the first part was technically successful and thus the part after && gets executed..

Thank you Akshay & Scrutinizer. It worked for me.

You specified to change the date only. Akshay Hegde's proposal will replace the time as well. To just replace the date part, try

Code:

sed "2s/=.*-.*-.*-/=$(date +"%Y-%m-%d" )-/" file