Using diff to compare the output of two commands

Question

How does one go about using diff to compare the output of two commands?

I know how to use it to compare the contents of a file filename1 with the output of a command cmd2:

cmd | diff filename -

How do I make it so that I can have another command, say cmd1 in place of filename?

I'm using dash, which doesn't support process substitution.

with process substitution diff <(cmd1) <(cmd2). – Apr 15 '19 at 02:29 — , Apr 15 '19 at 02:29
related https://unix.stackexchange.com/q/310500/72456 – αғsнιη Apr 15 '19 at 09:40 — αғsнιη, Apr 15 '19 at 09:40

Stephen Kitt · Accepted Answer · 2019-04-15T10:04:45.540

7

( cmd1 | ( cmd2 | ( diff /dev/fd/3 /dev/fd/4 ) 4<&0 ) 3<&0 )

edited Apr 15 '19 at 10:04

answered Apr 15 '19 at 07:32

Stephen Kitt

score 0 · Answer 2 · answered Nov 21 '19 at 21:47

0

easy :-)

$ cat file1 | diff /dev/stdin /dev/stderr 2<< EOT
> `cat file2`
> EOT
2c2
< 2
---
> 4

answered Nov 21 '19 at 21:47

defdefred

2 Answers2