Modify fstab in a bash function using sed

kb9mfd · 05-17-2014, 06:32 PM

I have a function to modify fstab using sed but I cannot get it to work correctly - ($1 = /dev/md0)

Code:

modify_fstab () {
  sed -i "s/LABEL=\/boot/$1/g" /etc/fstab
}

That gives a error because $1 has / in it, if I use single quotes the varible is not expanded. How do I get around that? Thanks!

Firerat · 05-17-2014, 06:49 PM

I usually use [ instead of /

.e.g

Code:

modify_fstab () {
  sed -i "s[LABEL=/boot[$1[g" /etc/fstab
}

You probably don't need the g, not that it matters

syg00 · 05-17-2014, 08:52 PM

It would pay to have a very good understanding of sed before screwing with fstab with -i. If you mess that up, you can't boot.

kb9mfd · 05-17-2014, 09:14 PM

Quote:

Originally Posted by Firerat

I usually use [ instead of /

.e.g

Code:

modify_fstab () {
  sed -i "s[LABEL=/boot[$1[g" /etc/fstab
}

You probably don't need the g, not that it matters

Thank you! I did not realize you can change the delimiter. It worked perfect.

kb9mfd · 05-17-2014, 09:19 PM

Quote:

Originally Posted by syg00

It would pay to have a very good understanding of sed before screwing with fstab with -i. If you mess that up, you can't boot.

Yes, good thing I am working on a non-production unit. I have tested and reloaded this machine about 6 times now to test all the scripts, this was the last thing I could not fully resolve. I was creating a script to convert it from a single drive to raid. Thanks!

(it was setting my boot to $1, it took took a couple of those reloads before I remebered to fix that before rebooting)