On Mon, Nov 17, 2014 at 09:49:32PM +0000, Stephane Chazelas wrote: > [tested on current git head > f6d4def4e27b13fab174e948b94cd10550d3e10e]
> Command substitution doesn't seem to work in $PS4 (used for > xtrace prompt): > $ PS4='$(date +%T)> ' dash -xc : > dash: 1: Syntax error: end of file unexpected (expecting ")") > And with the old syntax: > $ PS4='`date +%T`> ' dash -xc : > > : > And with more than one command: > $ PS4='`date +%T`> ' dash -xc ':;:' > > : > dash doesn't return and seems to go in a forking loop, > presumably because the `date` there triggers another PS4 > expansion and so on recursively > If I prevent the recursion with: > --- a/src/eval.c > +++ b/src/eval.c > @@ -776,7 +776,15 @@ evalcommand(union node *cmd, int flags) > int sep; > > out = &preverrout; > + > + /* > + * reset xflag temporarily for command substitutions performed > + * upon $PS4 expansion > + */ > + xflag = 0; > outstr(expandstr(ps4val()), out); > + xflag = 1; > + > sep = 0; > sep = eprintlist(out, varlist.list, sep); > eprintlist(out, arglist.list, sep); > $ PS4='`date +%T`> ' ./src/dash -xc ':;sleep 1; date' > > : > 21:43:47> sleep 1 > 21:43:48> date > Mon Nov 17 21:43:48 GMT 2014 > The command substitution still fails upon the first expansion > only. I quickly gave up trying to find out why as I found the > code there hard to follow. In FreeBSD sh, I have disabled command substitution in PS4 (POSIX does not require it anyway). It is treated as a syntax error. Talking about syntax errors, dash has a problem there as well. If there is a syntax error in PS4 and set -x is enabled, it will not execute any simple commands (assignments to PS4 cause an error and are subsequently reverted). FreeBSD sh prints the error messages and subsequently uses the raw unexpanded text. -- Jilles Tjoelker -- To unsubscribe from this list: send the line "unsubscribe dash" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
