cat - concatenate or write files, text or binary

cat > list.txt

aaa

bbb ccc Press CTRL+D to stop inputting and save file.

cat list.txt

aaa

bbb ccc

cat f1 f2

aaa bbb

cat f1 f2 > f3

cat f3

aaa bbb

cat >> f3

ddd

Append input to file.

cat f1 - f2 > f3 

This is what I entered in the middle.

cat f3

aaa

This is what I entered in the middle. bbb

cat video.001 video.002 video.003 > vid.avi

Joining split binary file.