Unix: removing duplicates from a file

Over the last few months, I have re-discovered some unix commands (it’s been such a long time)

• Eliminate duplicate lines from a file

#sort -u filename > filename.new

• List all lines that do not match a condition

#grep -v ajsk filename

• Copy contents of two files to one

#cat file1 file2 > file3

• Append output of a command to a file

#cat file1 >> file2