Database Reference
In-Depth Information
Line 8
Line 9
Line 10
Notice that with
tail
you have to add one. Removing the last three lines can be done
with
head
:
$
< lines head -n -3
Line 1
Line 2
Line 3
Line 4
Line 5
Line 6
Line 7
You can print (or extract) specific lines (4, 5, and 6 in this case) using either
sed
,
awk
,
or a combination of
head
and
tail
:
$
< lines sed -n
'4,6p'
$
< lines awk
'(NR>=4)&&(NR<=6)'
$
< lines head -n 6 | tail -n 3
Line 4
Line 5
Line 6
Print odd numbered lines with
sed
by specifying a start and a step, or with
awk
by
using the modulo operator:
$
< lines sed -n
'1~2p'
$
< lines awk
'NR%2'
Line 1
Line 3
Line 5
Line 7
Line 9
Printing even numbered lines works in a similar manner:
$
< lines sed -n
'0~2p'
$
< lines awk
'(NR+1)%2'
Line 2
Line 4
Line 6
Line 8
Line 10
Based on pattern
Sometimes you want to extract or remove lines based on their contents. Using
grep
,
the canonical command-line tool for filtering lines, we can print every line that
matches a certain pattern or regular expression. For example, to extract all the chap‐
ter headings from
Alice's Adventures in Wonderland
:
