How to extract lines when two columns strings are not equal

Question

I have a CSV file that looks like this format:

text1,text2,string1,string2
text3,text3,string3,string2
text4,text5,string1,string2
text6,text6,string6,string7

I want to extract rows when column1 and column2 are not equal. The expected result in the above example would be:

text1,text2,string1,string2
text4,text5,string1,string2

When column1 and column2 are not equal. I am familiar with commands that allow me extract specific column like the following to extract the first column:

cat input.csv | cut -d ',' -f1 > output.csv

Answer 1

Assuming that this is a simple CSV file, without any fancy embedding of commas or newlines within the fields of the actual data, you may use awk to do this:

awk -F ',' '$1 != $2' <input.csv

This is a shorthand way of writing

awk 'BEGIN { FS = "," } $1 != $2 { print }' <input.csv

and it sets the input field separator to a comma and prints each line if the first and second fields ($1 and $2) are not identical.

An equivalent Perl variant:

perl -F ',' -na -e 'print if $F[0] ne $F[1]' <input.csv

Answer 2

GNU sed solution:

sed -E '/^([^,]+,)\1/d' input.csv

The output:

text1,text2,string1,string2
text4,text5,string1,string2

Answer 3

$ awk -F "," '{if ($1 != $2)print $0}' filename
text1,text2,string1,string2
text4,text5,string1,string2