is there process substitution in Bourne Shell like that in Bash?

Question

I'm trying to use cmp to compare outputs of two commands (Bourne shell):

cmp <(ls $file1) <(ls $file2)

It works well in Bash but cannot work in Bourne. Is there any solution? Thanks so much!

Answer 1

Process substitution is (or used to be) implemented using named pipes. You could use mkfifo directly to recreate the same behavior:

mkfifo pipe1 pipe2
ls $file1 > pipe1 &
ls $file2 > pipe2 &
cmp pipe1 pipe2
rm pipe1 pipe2

But besides performances, you won't gain much compared to going thought regular files...