From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephane Chazelas Subject: command substitutions in $PS4 Date: Mon, 17 Nov 2014 21:49:32 +0000 Message-ID: <20141117214931.GA4601@chaz.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from plane.gmane.org ([80.91.229.3]:41670 "EHLO plane.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751464AbaKQVuO (ORCPT ); Mon, 17 Nov 2014 16:50:14 -0500 Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1XqUBZ-00034G-0p for dash@vger.kernel.org; Mon, 17 Nov 2014 22:50:13 +0100 Received: from 5ec33b79.skybroadband.com ([94.195.59.121]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Mon, 17 Nov 2014 22:50:13 +0100 Received: from stephane.chazelas by 5ec33b79.skybroadband.com with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Mon, 17 Nov 2014 22:50:13 +0100 Content-Disposition: inline Sender: dash-owner@vger.kernel.org List-Id: dash@vger.kernel.org To: dash@vger.kernel.org Hello. [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. -- Stephane