Using "ifne" in a pipeline – running multiple commands In my script, I am using the `ifne` utility from the `moreutils` package. The line can be simplified to the following: printf "asdf\n" | ifne cat - && echo "stream not empty" `ifne` executes only if the stream is non-empty. But how can I make the second command (`echo "stream not empty"`) also execute only if the stream is non-empty? For example, how can change the following command so that it doesn't print "stream not empty"? printf "" | ifne cat - && echo "stream not empty" Surrounding `cat` and `echo` with parentheses generates a syntax error: printf "" | ifne (cat - && echo "stream not empty") How can I execute the last command only if stream is non-empty?

`ifne` doesn't set an exit code based on whether the input is empty or not, so `&&` and `||` aren't going to work as hoped. An alternate approach to Babyy's answer is to use `pee` from the same package:


printf "asdf\
" | pee 'ifne cat -' 'ifne echo "stream not empty"'


This works like `tee`, but duplicates the input stream into a number of pipes, treating each argument as a command to run. (`tpipe` is a similar command, but behaves slightly differently.)

A possible issue though is that each of the commands may be writing to stdout in parallel, depending on buffering and length of input/output there is a chance that output will be interleaved, or vary from run to run (effectively a race). This can probably be eliminated using `sponge` (same package) instead of `cat`, and/or other buffering/unbuffering solutions. It affects the example you gave, but may not affect your real use-case.