CODEWITHSUNDEEP
linuxbash
Alex
Alex

Reputation: 43

Script which subtract two file sizes

I would like to subtract sizes of two files. I found location of that files and then I used command: 

du -h /bin/ip | cut -d "K" -f1

I got 508 and I wanted to create variable 

x=$((du -h /bin/ip | cut -d "K" -f1))

but at the result I got

"-bash: du -h /bin/ip | cut -d 'K' -f1: division by 0 (error token is "bin/ip | cut -d 'K' -f1")"

What did I do wrong? How can i put this value in variable?

Upvotes: 1

Views: 279

Answers (2)

KamilCuk
KamilCuk

Reputation: 140960

What did I do wrong?

You used arithmetic expansion $(( ... )) instead of a command substitution $( ... ). As a result shell interpreted /bin as / as division and bin as 0 (because there is no variable named bin) and tried to divide by 0.

How can i put this value in variable?

Use a command substitution:

x=$(du -h /bin/ip | cut -d "K" -f1)

But it would be way more reliable to use stat for collecting information about files:

x=$(stat -c %s /bin/ip)

To substract two file sizes, you can again use command substitutions to get the size, but use arithmetic expansion to calculate the difference.

difference=$(( $(stat -c %s file1) - $(stat -c %s file2) ))

Upvotes: 2

choroba
choroba

Reputation: 241828

Perl to the rescue!

perl -le 'print((-s "file1.txt") - (-s "file2.txt"))'
  • -l adds newline to print
  • -s returns a file size (see -x)

Upvotes: 0

Related Questions