CODEWITHSUNDEEP
javaregexunix
Iulian Rosca
Iulian Rosca

Reputation: 1015

Use regex or unix to select specific columns

I am using Runtime.getRuntime().exec("df") to get the space details for my partitions.

Filesystem     1K-blocks    Used Available Use% Mounted on
/dev/sdb12      41022792 4219168  34713128  11% /
udev             8103980       4   8103976   1% /dev
tmpfs            3245332     924   3244408   1% /run
none                5120       0      5120   0% /run/lock
none             8113328     160   8113168   1% /run/shm
/dev/sdb2         262144   28584    233560  11% /boot/efi

How can I use regex or UNIX commands to get as the output just the 2nd,3rd and 4th columns - changing the headers as follows - Available Memory, Used Memory and Total memory exactly in this order.
So the desired output is : 

Available    Used     Total
34713128   4219168    41022792
8103976       4       8103980
3244408      924      3245332
             ...

Thank you!

Upvotes: 1

Views: 255

Answers (3)

Floris
Floris

Reputation: 46375

The following rather long string does what you ask:

df | awk 'BEGIN {print "   Available        Used       Total";} {if (NR>1)  printf("%12d%12d%12d\n", $4, $3, $2);}'

Explanation:

| awk          take the output of the df command as input to awk
BEGIN          do this first: print headers. Note the use of spaces to align things
if (NR > 1)    skip "record 1" = do not do anything with the headers
printf()       do formatted printing
%12d           print integer in fixed width of 12 characters (maintains alignment

Result on my machine:

   Available        Used       Total
    71644456   551306776   623463232
           0         372         372
           0           0           0
           0           0           0
   407510704   377391216   784901920
   618400760   549288520  1167689280

Not terribly useful without the name of the disks, but this is what you were asking...

Upvotes: 2

maaartinus
maaartinus

Reputation: 46432

For me this works

df | perl -pe \
  's!^(?:\S+\s+){2}(\S+)\s+(\S+).*!"$1\t$2\t" . ($1 eq "Used" ? "Total" : $1 + $2)!e'

It's not nice: It finds the columns as non-blanks separated by blanks, which is a bit fragile. It computes the last column as the sum or "Total" based on the column name. Rather fragile, I'd say.

Upvotes: 0

asthasr
asthasr

Reputation: 9407

You can use awk to do this:

df | awk '{print ""$4" "$3" "$2""}'

Upvotes: 0

Related Questions