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I'm working on a bash script that backs up a configuration file before copying over a new file.

Here's what my snippet looks like:

mv ~/myStuff.conf  ~/myStuff.conf.bak
cp ~/new/myStuff.conf ~/myStuff.conf

Every time this script is run, I'd like there the backup to have a unix timestamp in the filename. I tried this

DATEVAR=date +%s
mv ~/myStuff.conf  ~/myStuff.conf.$DATEVAR.bak

But this doesn't work, since the date function doesn't execute and bash sees it as a string, and the resulting file ends up being

Any ideas on how to get the results of the date function into a variable?

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up vote 4 down vote accepted

This is possible with command substitution.

DATEVAR=$(date +%s)
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export datevar=`date` # date embedded in backquotes


echo $datevar

Lun 25 Gen 2016 15:56:14 CET
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Besides correctly formatting for code, an explanation of what is going on would improve this answer. – Nattgew Jan 25 at 15:51
Well, Nattgew FYI: export makes the variable available in the environment to be used in next steps. Backquotes surround a bash-command that will be executed. I thought superusers are supposed to know these basics, but of course we have to think of readers who arrive here via any search engine :-) – Klaas-Z4us-V Jan 26 at 9:40
For bash you may read any shell and I used the command without parameters to see what is the default. – Klaas-Z4us-V Jan 26 at 9:49

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