From: Bart Schaefer <schaefer@brasslantern.com>
To: zsh-workers@sunsite.dk
Subject: Value of $? after signal
Date: Sat, 8 Sep 2001 06:50:25 +0000 [thread overview]
Message-ID: <1010908065025.ZM18493@candle.brasslantern.com> (raw)
The manual says under the "return" builtin:
If return was executed from a trap in a TRAPNAL function, the
effect is different for zero and non-zero return status. With zero
status (or after an implicit return at the end of the trap), the
shell will return to whatever it was previously processing; with a
non-zero status, the shell will behave as interrupted except that
the return status of the trap is retained. Note that the numeric
value of the signal which caused the trap is passed as the first
argument, so the statement `return $((128+$1))' will return the
same status as if the signal had not been trapped.
This is the only reference I can find to "exit status == 128 plus signal"
in the zsh manual, but the bash2 manual says in the "simple command"
grammar:
The return value of a simple command is its exit status,
or 128+n if the command is terminated by signal n.
Both zsh and bash appear to do this, i.e. if you interrupt "sleep 10" with
a ^C (SIGINT), $? is set to 130 in both shells.
The odd bit is what happens when a command is stopped with ^Z (SIGSTOP) or
with any other stop-signal (STOP, TTOU, etc.). In this case bash sets $?
to 0, but zsh sets it to the signal number -- not 128+n, but n. So, e.g.,
if you ^Z mutt, which catches TSTP and then sends itself STOP, you get $?
set to 19; but if you ^Z any command that doesn't catch TSTP, you get $?
set to 20.
I guess the reasoning in zsh is to not add 128 if the command has not been
terminated, but still report the signal number? Or was the intent to use
128+n and we simply forgot the 128 somewhere? Does anybody remember how
we arrived at this behavior?
--
Bart Schaefer Brass Lantern Enterprises
http://www.well.com/user/barts http://www.brasslantern.com
Zsh: http://www.zsh.org | PHPerl Project: http://phperl.sourceforge.net
next reply other threads:[~2001-09-08 6:50 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-09-08 6:50 Bart Schaefer [this message]
[not found] <200109101450.KAA75715@raptor.research.att.com>
2001-09-11 14:36 ` Bart Schaefer
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1010908065025.ZM18493@candle.brasslantern.com \
--to=schaefer@brasslantern.com \
--cc=zsh-workers@sunsite.dk \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://git.vuxu.org/mirror/zsh/
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).