On Sun, Nov 06, 2016 at 03:25:33PM +0100, Lars Schneider wrote:
> This looks good to me (and it works on my machine).
> However, I took a look at the "write_script" function and found this,
> added by Junio in 840c519d:
>
> echo "#!${2-"$SHELL_PATH"}" &&
>
> There is some kind of variable expansion happening with the "2-" but
> I can't quite figure out what is going on. Plus, I can't find anything
> about this in the sh docs.
>
> Can anyone help me to understand it?
See the section on parameter expansion in "man bash". Basically:
${foo:-bar}
expands to $foo, or "bar" if it is unset or empty. Without the colon:
${foo-bar}
expands to $foo, "bar" if it unset (but not if it is empty). I don't
think we really care about the distinction here, and either is fine (you
would not ever pass an empty argument).
So in this context you may pass in the interpreter:
write_script "$PERL_PATH" <<\EOF
... some perl code ...
EOF
or it defaults to shell, which is what most of the callers want:
write_script <<\EOF
... some shell code ...
EOF
-Peff