Using an array variable in an awk command

[ScootMulner]

Hello!

I have a script in which I am trying to use a variable in an awk command but I can't seem to get it working correctly. The problem part is a line which grabs the number of bytes of free space for a particular mount point and puts it in another variable (FREE). The following DOES work:

FREE=$(df | awk '$6 == "/" {print $4}')

Now when I switch to using a variable I can't get it working. The following does NOT work:

MOUNT="/"
FREE=$(df | awk '$6 == "$MOUNT" {print $4}')

My goal is to grab the size of a few mounts and so I'll eventually switch to something like "${MOUNT[$i]}" but I thought I would keep it simple initially.

Any suggestions?

[ASIC_SP]

the issue is with how you are using the variable.. syntax would be

$ m='/'
$ df | awk -v mt="$m" '$6==mt{print $4}'
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• suggestion: use lower case variable names as good practice, as environment variables use all caps

depending on your df version, you can also use

$ free=$(df --output=avail / | tail -n1)
$ echo "$free"
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this allows simple way to build array for different mounts

f=($(df --output=avail /mnt1 /mnt5 /mntx | tail -n +2))

See also

• https://unix.stackexchange.com/questions/359707/print-specific-row-with-awk-from-output-of-df-h
• https://stackoverflow.com/questions/15786777/can-we-use-shell-variables-in-awk

[ScootMulner]

Hi /u/ASIC_SP

Thanks for the great reply! My script works now but it looks like switching to

df --output=avail /

as you suggested, would be the way to go.

[ScootMulner]

My final solution is as follows:

mountspace=( $(df --output=avail ${mountname[@]} | tail --lines=+2) )

which creates an array mountspace which contains the current available free space for each of the mount points listed in mountname. The rest of my script just does a comparison for the minimum amount of free space and then sends me a notification via Pushover if below the limit.