Delete several lines from a file using grep

Question

I have a file with multiple lines which looks like that :

brand,model,inches,price

dell       xps      13    9000     
macbook    pro      13    13000
asus       zenbook  13    10500

I want to delete the lines where the price is more than 10000. I want to ask if it is possible by using grep?

Answer 1

You can use the following to get the lines where price is greater than 10000 :

$ grep -E '.* [0]*[1-9][0-9]{4,}$' file.txt 
macbook    pro      13    13000
asus       zenbook  13    10500

If you want to remove those lines add -v :

$ grep -vE '.* [0]*[1-9][0-9]{4,}$' file.txt 
dell       xps      13    9000     

• .* will match all characters upto the last column containing prices

• [1-9] will match the first digit of the price

• [0-9]{4,}$ will match 4 or more digits after the first digit so we have a total of five digits meaning 10000 or greater

Answer 2

It's possible, but grep uses regular expressions that operate on strings, not numbers.

grep -v '[0-9]\{5\}$' input.txt

-v removes the matching lines. [0-9] matches any digit, \{n\} means the preceding thing is repeated n times (5 times in this case, i.e. 10000 and more). $ matches the line end.

awk can compare numbers, so it's more suitable for the job:

awk '$4<10000{print}' input.txt

or Perl:

perl -ane 'print if $F[-1] < 10000' input.txt

Answer 3

Given your sample input:

$ cat /tmp/foo
dell       xps      13    9000
macbook    pro      13    13000
asus       zenbook  13    10500

You can use awk:

$ awk '{ if ($4 <= 10000) print; }' /tmp/foo
dell       xps      13    9000

Answer 4

try

cp input.txt original.txt
awk 'NR==1 || $4 < 10000 ' original.txt > input.txt

where

• condition with NR==1 to keep header line.