I notice that the hush parameter expansion ${parameter:+word} is backwards compared to bash.

Here is a test case comparing 'u-boot hush' against 'debian bash'. It shows that at lines 4 and 8, the results are backwards:

shell command result u-boot hush result debian-bash ------------------------------------- --------------------- --------------------- 1. var='' 2. echo "${var} = (${var})" ${var} = () ${var} = () 3. echo "${var:-bbbb} = (${var:-bbbb})" ${var:-bbbb} = (bbbb) ${var:-bbbb} = (bbbb) 4. echo "${var:+cccc} = (${var:+cccc})" ${var:+cccc} = (cccc) ${var:+cccc} = ()

5. var='aaaa' 6. echo "${var} = (${var})" ${var} = (aaaa) ${var} = (aaaa) 7. echo "${var:-bbbb} = (${var:-bbbb})" ${var:-bbbb} = (aaaa) ${var:-bbbb} = (aaaa) 8. echo "${var:+cccc} = (${var:+cccc})" ${var:+cccc} = () ${var:+cccc} = (cccc)

The bash manual says at: https://www.gnu.org/software/bash/manual/html_node/Shell-Parameter-Expansion...

${parameter:+word} ------------------ If parameter is null or unset, nothing is substituted, otherwise the expansion of word is substituted.

Example: -------- $ var=123 $ echo ${var:+var is set and not null} var is set and not null