rc.subr add Exists so we can find sed

[sjg]

Summary

SED=Exists -x /usr/bin/sed /rescue/sed

avoids adding /rescure to $PATH, and allows use of sed
before /usr is mounted (if a separate filesystem).

[jlduran]

This looks good. It makes an extra effort to find sed.
I just wonder if it is possible to define SED=${SED:-$(Exists -x /usr/bin/sed /rescue/sed)} only once in rc.subr, maybe at the beginning?
ShellCheck usually recommends avoiding backticks (https://www.shellcheck.net/wiki/SC2006).

[sjg]

In D43826#999880, @jlduran_gmail.com wrote:

This looks good. It makes an extra effort to find sed.
I just wonder if it is possible to define SED=${SED:-$(Exists -x /usr/bin/sed /rescue/sed)} only once in rc.subr, maybe at the beginning?

we could but it is only needed if /usr isn't mounted which is checked by have basename
the extra SED=${SED:- in rc_trace is just incase that is called from local.rc.subr before we check for basename.

ShellCheck usually recommends avoiding backticks (https://www.shellcheck.net/wiki/SC2006).

old habits...

[sjg]

Use $() rather than backticks, and only look once.