How to cut lines in a file by criteria?

Question

bash

Hello colleagues. The task is this. I have an input - a .txt file that has lines, each containing entries like 55555,dif and 55555,bat. How do I cut only those lines that contain a dif in the string? Perhaps with cut or something else?

Answer 1

grep -v dif file.txt > out.txt

Answer 2

sed -i.bak '/dif/d' filename.txt
filename.txtLines that contain text will be removed from the file dif. The file will be backed up before changes.

Answer 3

for kit, on awk:
awk '!/dif/' file.txt