Test data

Test input (file pg.txt inside pg.7z): https://disk.yandex.ru/d/mOY5CrveIAOtnQ

7z e pg.7z

Reference output (file pgref.txt inside pgref.txt.7z): https://disk.yandex.ru/d/p3W1pGZwj95PAQ

7z e pgref.txt.7z

How to test:

./freq pg.txt out.txt
md5sum out.txt pgref.txt

MD5 sums for different line endings:

850944413ba9fd1dbf2b9694abaa930d *lf.txt
d1362c6c9de664c34c3066ec1d01078f *crlf.txt

One also can generate reference output (file pgref.txt) manually:

bash freq.sh pg.txt pgref.txt