Question

in UNIX scripting programming, cat is a command that could combine 2 files together:

cat file1 file2 > file3

this generate the 3rd by combining the first two.

also, cat could be used with pipe:

cat file1 | tail -4

this will list the last 4 lines of file 1.

question: how could I combine the last 4 lines of file 1 and 2, to generate file 3?

i’m a bit lost here: how to give 2 streams inputs to cat?

Answer 1

Bash has a process substitution feature:

  cat <(tail -4 file1) <(tail -4 file2)

I often use this feature to diff slightly altered versions of two files.