Re: Doc on simple command expansion

[Greg Wooledge]

On Thu, Mar 03, 2022 at 07:11:51PM +0800, Glen Huang wrote:
> Hi,
> 
> I'm having difficulty understanding this paragraph from Bash Reference
> Manual Chapter 3.7.1.
> 
> > If one of the expansions contained a command substitution, the exit status 
> > of the command
> > is the exit status of the last command substitution performed. If there 
> > were no command
> > substitutions, the command exits with a status of zero.
> 
> Which seems to indicate that for a simple command like this
> 
> echo "$(false)"

You took this quote out of context.  From the man page, here's the whole
paragraph:

       If there is a command name left after expansion, execution proceeds  as
       described  below.   Otherwise, the command exits.  If one of the expan‐
       sions contained a command substitution, the exit status of the  command
       is  the  exit  status  of  the last command substitution performed.  If
       there were no command substitutions, the command exits with a status of
       zero.

The piece that you quoted only applies in the "Otherwise" case, when
there is no command name after expansions.  An example of this would
be:

unicorn:~$ q=$(false)
unicorn:~$ echo "$?"
1