Built in Variables

df -h > size.txt

awk '{ print $1, $2, $3 }' abc.txt

abc def ghi
jkl mno pqr
stu vwx yz

awk '{ print $1 }' abc.txt
# Output:
abc
jkl
stu

awk '{ print $2 }' abc.txt
# Output:
def
mno
vwx

awk '{ print $3 }' abc.txt
# Output:
ghi
pqr
yz

awk '{ print NR, $1, $4 }' size.txt

1 Filesystem Avail
2 udev       1.8G
3 tmpfs      356M
4 /dev/sda1  9.3G
...

awk 'NR == 8 { print $4 }' size.txt
# Output:
360G

awk '{ print NF }' size.txt

7
6
6
6
6
6
6
6
6

awk '{ print NR, NF }' size.txt

1 7
2 6
3 6
4 6
...

awk '{ print "Line", NR, "has", NF, "fields" }' size.txt

Line 1 has 7 fields
Line 2 has 6 fields
...

awk '{ print $NF }' size.txt

on
/dev
/run
/
...

awk '{ print FILENAME, $1 }' size.txt

size.txt Filesystem
size.txt udev
size.txt tmpfs
...

df -h | awk '{ print FILENAME, $1 }'
# Output:
 Filesystem
 udev
 tmpfs
 ...

awk -F, '{ print $1, $NF }' data.csv