user@linux:~ $ file /tmp/t.txt*
/tmp/t.txt: ASCII text, with CRLF line terminators

user@linux:~ $ perl -i.bak -pe 's/\r\n/\n/'  /tmp/t.txt 

user@linux:~ $ file /tmp/t.txt*
/tmp/t.txt:     ASCII text
/tmp/t.txt.bak: ASCII text, with CRLF line terminators