Possible bug in how OpenBSD ksh(1) handle the ERR trap

[phillbush]

To help me identify whether a command fails and what is its exit code, I trap the ERR special signal to print the exit code of a command that returns nonzero.

trap 'printf "\e[1;31mEXIT: %s\e[0m\n" "$?"' ERR

You can try it in your shell.
Run this and then run `false` or `cat nonexistent/file.txt`.

However, OpenBSD pdksh behaves a little different from ksh93 and bash when the command terminates from a signal.

For example. Try this in bash(1) or ksh93(1): run the trap command and then run `cat` (without any arguments) and immediately type `^C` (ctrl+c) to send `SIGINT` to cat. The shell will print `EXIT: 130` (or `EXIT: 258`) right after the command is terminated and before the next prompt.

Try this again in OpenBSD ksh(1). The `EXIT: 130` string will not be printed immediately. Now enter a successful command, such as grep(1) or ls(1). NOW the error string will be printed.

This image illustrates what I am saying:

• First, I'm on a ksh93(1) subshell.
  I run `false`, and it prints `EXIT: 1`.
  I run `cat` and type `^C` and it prints `EXIT 258`.
  I run `grep -V` and it prints nothing.
• Then, I exit ksh93(1) and return to ksh(1).
  I run `false`, and it prints `EXIT: 1`.
  I run `cat` and type `^C` and it prints nothing.
  I run `grep -V` and it prints `EXIT 130`.

Is this a bug? If yes, is it known by the developers?
I think that it can be a problem in a script to not handle a ERR trap right after a command terminates from a signal.

[ibara]

Probably want to report this to bugs@

[phillbush]

Originally Posted by ibara

Probably want to report this to bugs@

I want to certify that this is not happening only with me.
Someone on #openbsd IRC channel tried to replicate the bug and nothing happened... the "EXIT: 130" string was not printed after true(1).
Could you replicate the bug?

[ibara]

On ksh(1):
false
EXIT: 1

cat
^C
(no output, but if you run echo $? you see 130)

true
(no output)

[phillbush]

Originally Posted by ibara

On ksh(1):
false
EXIT: 1

cat
^C
(no output, but if you run echo $? you see 130)

true
(no output)

What happens if you use a non-builtin (like ls(1)) in place of true?

[Head_on_a_Stick]

Hopefully not off-topic but this is from Alpine Linux running ibara's port of OpenBSD's ksh(1):

~$ trap 'printf "\e[1;31mEXIT: %s\e[0m\n" "$?"' ERR
~$ false
EXIT: 1
1~$ cat
^C
130~$ ls
[snip]
EXIT: 0
~$

Note my prompt, which shows the exit status of the last command if it is non-zero:

~$ echo $PS1
\e[91m${?#0}\e[0m\w\e[97m$\e[0m
~$

[phillbush]

Just sent the bug to bugs@.