* Bash monitor mode remains enabled if disabled in .bashrc
@ 2017-08-30 23:26 Michel LaBarre
2017-08-31 12:31 ` cyg Simple
0 siblings, 1 reply; 3+ messages in thread
From: Michel LaBarre @ 2017-08-30 23:26 UTC (permalink / raw)
To: cygwin
Playing with set -m/+m and shopt -s lastpipe, in an interactive bash shell,
I came across a situation
which is minor unless it has broader implications for others that I do not
know about.
Specifically if "set +m" is present in .bashrc, it looks like job control
(monitor mode) is off
in an interactive shell (as per "echo $-") but it is actually on.
I ran into this with "shopt -s lastpipe" behaviour with and without job
control.
I can also reproduce it with "sleep 25&" then "fg" will fail with "no job
control".
If I "set +m" within the interactive shell rather than, or in addition to,
.bashrc, both the
flags ($-) and behaviour (lastpipe and fg) reflect job control being off.
I include only an example with lastpipe.
FYI - from bash reference for shopt:
lastpipe If set, and job control is not active, the shell runs the last
command
of a pipeline not executed in the background in the current shell
environment.
My .bashrc includes "shopt -s lastpipe" and "set +m".
My objective was to produce the same conditions as within a script for
debugging a messy statement at a command line
and I had no need for job control while doing this and I would sometimes
forget to disable monitor mode after a new bash.
If somebody trying to debug some bash statements and is unaware that a
second "set +m" is required, they
might be confused for a bit. (An option to make an interactive shell behave
the same as a non-interactive shell
might facilitate such debugging.)
C:\mybin>bash
$ echo "$-" # no "m" meaning monitor mode is off i.e.
no job control...
hiBHs
$ echo abc | read zot # zot is therefore in a sub-process hence value
not available in this process
$ echo $zot
$ set +m
$ echo "$-" # still no m but behaviour is
different...
hiBHs
$ echo abc | read zot # read zot now running in this process so value is
available
$ echo $zot
abc
$ bash --version
GNU bash, version 4.4.12(3)-release (x86_64-unknown-cygwin)
By the way, the "s" set option ($- above) is not defined in the bash
reference manual that I have and is not accepted
by the "set" built into bash so I don't know how it gets set. (i.e."set -s
s" or "set +s s" both fail with "invalid option".)
Michel LaBarre
--
Problem reports: http://cygwin.com/problems.html
FAQ: http://cygwin.com/faq/
Documentation: http://cygwin.com/docs.html
Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Bash monitor mode remains enabled if disabled in .bashrc
2017-08-30 23:26 Bash monitor mode remains enabled if disabled in .bashrc Michel LaBarre
@ 2017-08-31 12:31 ` cyg Simple
[not found] ` <000601d32265$f9f85880$ede90980$@rogers.com>
0 siblings, 1 reply; 3+ messages in thread
From: cyg Simple @ 2017-08-31 12:31 UTC (permalink / raw)
To: cygwin
On 8/30/2017 7:26 PM, Michel LaBarre wrote:
> Playing with set -m/+m and shopt -s lastpipe, in an interactive bash shell,
> I came across a situation
> which is minor unless it has broader implications for others that I do not
> know about.
>
> Specifically if "set +m" is present in .bashrc, it looks like job control
> (monitor mode) is off
> in an interactive shell (as per "echo $-") but it is actually on.
>
> I ran into this with "shopt -s lastpipe" behaviour with and without job
> control.
> I can also reproduce it with "sleep 25&" then "fg" will fail with "no job
> control".
>
> If I "set +m" within the interactive shell rather than, or in addition to,
> .bashrc, both the
> flags ($-) and behaviour (lastpipe and fg) reflect job control being off.
>
Are you sure that .bashrc is being sourced? The initial start of an
interactive shell doesn't read .bashrc by default. It reads
.bash_profile when starting interactive mode. Now most likely your
.bash_profile contains lines to check the existence of .bashrc and
source it but you need to check.
--
cyg Simple
--
Problem reports: http://cygwin.com/problems.html
FAQ: http://cygwin.com/faq/
Documentation: http://cygwin.com/docs.html
Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2017-08-31 15:50 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2017-08-30 23:26 Bash monitor mode remains enabled if disabled in .bashrc Michel LaBarre
2017-08-31 12:31 ` cyg Simple
[not found] ` <000601d32265$f9f85880$ede90980$@rogers.com>
2017-08-31 15:50 ` cyg Simple
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 read-only IMAP folder(s) and NNTP newsgroup(s).