From: Yaroslav Halchenko <yoh@onerussian.com>
To: dash@vger.kernel.org
Cc: Kyle Meyer <kyle@kyleam.com>
Subject: stalls whenever PS4 contains $() and set -x
Date: Mon, 25 May 2020 09:41:15 -0400 [thread overview]
Message-ID: <20200525134115.GO423431@lena.dartmouth.edu> (raw)
Dear DASH maintainer(s),
I like to (ab)use PS4 and set -x for tracing execution of scripts.
Reporting time and PID is very useful in this context.
I am not 100% certain if bash's behavior (of actually running the command
embedded within PS4 string, probably eval'ing it) is actually POSIX
compliant, posh seems to not do that; but I think it is definitely not
desired for dash to just stall:
- the script:
#!/bin/sh
set -x
export PS4='+ $(date +%T.%N) [$$] '
echo "lets go"
sleep 1
echo "done $var"
- bash:
/tmp > bash --posix test.sh
+export 'PS4=+ $(date +%T.%N) [$$] '
+PS4='+ $(date +%T.%N) [$$] '
+ 09:15:48.982296333 [2764323] echo 'lets go'
lets go
+ 09:15:48.987829613 [2764323] sleep 1
+ 09:15:49.994485037 [2764323] echo 'done '
done
- posh:
exit:130 /tmp > posh test.sh
+export PS4=+ $(date +%T.%N) [$$]
+ $(date +%T.%N) [$$] echo lets go
lets go
+ $(date +%T.%N) [$$] sleep 1
+ $(date +%T.%N) [$$] echo done
done
- dash: (stalls it set -x)
/tmp > dash test.sh
+export PS4=+ $(date +%T.%N) [$$]
^C^C
--
Yaroslav O. Halchenko
Center for Open Neuroscience http://centerforopenneuroscience.org
Dartmouth College, 419 Moore Hall, Hinman Box 6207, Hanover, NH 03755
Phone: +1 (603) 646-9834 Fax: +1 (603) 646-1419
WWW: http://www.linkedin.com/in/yarik
next reply other threads:[~2020-05-25 14:25 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-25 13:41 Yaroslav Halchenko [this message]
2020-05-27 3:19 ` [PATCH] eval: Prevent recursive PS4 expansion Herbert Xu
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