joined command lines in history by LF

[HIROSE Masaaki]

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 goa 4.15.0-47-generic #50-Ubuntu SMP Wed Mar 13
10:44:52 UTC 2019 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:

I set the following environment variable:
  - export HISTTIMEFORMAT='%Y-%m-%d %T '
    to show timestamp in history
  - export PROMPT_COMMAND='history -a; history -n'
    to share history between different terminals

In this environment sometimes command lines in history are joined by LF.


Repeat-By:

I've tested the following environments
  - Ubuntu 18.04
    - bash 4.4.18-2ubuntu1
    - bash 4.4.12 (built by me)
    - bash 4.4.18 (built by me)
    - bash 5.0  (built by me)
  - CentOS 6.5
    - bash 4.4.18  (built by me)


- case-1
# invoke plain bash
env - bash --noprofile --norc

# set environment variables
export HISTTIMEFORMAT='%Y-%m-%d %T '
export PROMPT_COMMAND='history -a; history -n'

# clear history
rm -f ~/.bash_history
history -c
history -r

# execute some commands
ls
cd
df

# show history
history
    1  2019-05-16 19:42:06 history -r
    2  2019-05-16 19:42:00 export PROMPT_COMMAND='history -a; history -n'
export PROMPT_COMMAND='history -a; history -n'
    3  2019-05-16 19:42:02 rm -f ~/.bash_history
rm -f ~/.bash_history
    4  2019-05-16 19:42:08 ls
ls
    5  2019-05-16 19:42:09 cd
cd
    6  2019-05-16 19:42:11 df
df
    7  2019-05-16 19:42:13 history

# type <C-p>
bash-4.4$ history ^Jhistory

# type <C-p>
bash-4.4$ df^Jdf

- case-2
Use 2 terminals (T1 and T2)

@T1
env - bash --noprofile --norc
export HISTTIMEFORMAT='%Y-%m-%d %T '
export PROMPT_COMMAND='history -a; history -n'

@T2
env - bash --noprofile --norc
export HISTTIMEFORMAT='%Y-%m-%d %T '
export PROMPT_COMMAND='history -a; history -n'

@T1
rm -f ~/.bash_history
history -c

@T2
history -c

@T1
ls

@T2
pwd
# history 1 is joined by LF
history
    1  2019-05-16 20:26:29 pwd
ls
    2  2019-05-16 20:26:30 history

@T1
df
# history 2 is joined by LF
history
    1  2019-05-16 20:26:28 ls
    2  2019-05-16 20:26:57 df
ls
    3  2019-05-16 20:26:30 history
    4  2019-05-16 20:26:57 df
    5  2019-05-16 20:26:58 history