Date:Fri, 22 Nov 2019 16:16:58 +0800
From:Clark Wang
Message-ID:
| Curious why people care about this?
For some people it seems to be related to wanting to see $? in their
prompt, and either have it explicit that a SIGINT interrupted command
entry, or continue with previous $? ..
For me it is partly just because of what $? is. From posix:
? Expands to the decimal exit status of the most recent pipeline
(see Section 2.9.2).
nothing about being altered by anything other than (at least attempted)
execution of a pipeline (ie: some command or other).
More practically, the times when I want it are when I have run a command,
then start typing the next one, and realise that I really meant to check
the exit status of the last one before running another. If I finish typing
my next command I just mentally curse my forgetfulness, and take whatever
action I can (often re-running the previous command, if that makes sense).
But if I catch it before I have finished the next command, I have the
opportunity to abort what I'm doing, and check $? before it is lost.
If that happens while still on the first (or only) line of the new command,
then a line kill char (^U often) is OK, deletes whatever I typed, and I
can replace that with "echo $?" or whatever.
But if it happens after a \n has been entered, that no longer works,
whereas SIGINT (^C usually) does:
Compare bash...
jinx$ false
jinx$ while sleep 3
do
^C
jinx$ echo $?
130
(in bash my PS2 is set to be (become really) invisible so I can cut/paste
whole command sequences)
to the NetBSD sh (where editline doesn't handle my PS2 "properly")
[jinx]{2}$ false
[jinx]{2}$ while sleep 3
> do
>
[jinx]{2}$ echo $?
1
[jinx]{2}$ true
[jinx]{2}$ while sleep 3
> do
>
[jinx]{2}$ echo $?
0
(there was a ^C, not echoed explicitly, after the PS2 prompt on the line
after each "do" ... the lack of the echo another difference between editline
and readline I assume, the ^C is echoed if I disable editline and just
use the tty driver, my PS2 also works as planned then).
[jinx]{2}$ set +V
[jinx]{2}$ true
[jinx]{2}$ while sleep 3
do
^C
[jinx]{2}$ echo $?
0
kre
