The man page of bash (Special Parameters section) says:
? expands to the exit status of the most
recently executed foreground pipeline.
Nevertheless, background commands also modify the
value of this variable.
Example:
esoriano@omac:~$ false
esoriano@omac:~$ sleep 2 &
(wait 3 seconds)
esoriano@omac:~$ echo $?
0
esoriano@omac:~$
In this example, the most recently executed foreground
command is false, so the value of $? should be 1.
Configuration Information [Automatically generated, do not change]:
Machine: x86_64
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS: -DPROGRAM='bash' -DCONF_HOSTTYPE='x86_64'
-DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='x86_64-pc-linux-gnu'
-DCONF_VENDOR='pc' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash' -DSHELL
-DHAVE_CONFIG_H -I. -I../. -I.././include -I.././lib -Wdate-time
-D_FORTIFY_SOURCE=2 -g -O2 -fdebug-prefix-map=/build/bash-vEMnMR/bash-4.4.18=.
-fstack-protector-strong -Wformat -Werror=format-security -Wall
-Wno-parentheses -Wno-format-security
uname output: Linux omac 4.15.0-34-generic #37-Ubuntu SMP Mon Aug 27 15:21:48
UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
Machine Type: x86_64-pc-linux-gnu
Bash Version: 4.4
Patch Level: 19
Release Status: release
Description:
[Detailed description of the problem, suggestion, or complaint.]
Repeat-By:
[Describe the sequence of events that causes the problem
to occur.]
Fix:
[Description of how to fix the problem. If you don't know a
fix for the problem, don't include this section.]
