Re: Timestamp of last entry of command history is different than the last modified time of .bash_history. Is this the proper logic?

[David Wright]

On Fri 25 Jul 2025 at 21:52:36 (+0000), Veronica Cisneros wrote:
> Utterly confused by the timestamp of the last item of command history vs. the 
> last modified time of .bash_history
> 
> I configured all users with HISTTIMEFORMAT="%Y%m%dT%H%M%S%z "
> 
> Below I quote anonymized output from bash to commands date, history 12, and 
> alias lis (i.e., "ls -Zilas")
> 
> someUser:~$ date
> Wed Jul 23 07:12:56 PM PDT 2025
> someUser:~$ history 12
> 1262 20250723T184953-0700 journalctl | grep -F "Jul 23" | grep DBus
> 1263 20250723T185529-0700 tail /home/anotherUser/.bash_history
> 1264 20250723T185726-0700 lis /home/anotherUser/.*
> 1265 20250723T190000-0700 vim /etc/bash.bashrc
> 1266 20250723T190115-0700 whereis history
> 1267 20250723T190138-0700 man history
> 1268 20250723T190229-0700 man -K bash
> 1269 20250723T191113-0700 journalctl | grep "Jul 23" | grep "DBus"
> 1270 20250723T191221-0700 history 10
> 1271 20250723T191240-0700 lis .bash*
> 1272 20250723T191256-0700 date
> 1273 20250723T191303-0700 history 12
> someUser:~$ lis .bash*
> 45408 4 -rw-r--r-- 1 root root ? 46 Jul 9 19:21 .bash_aliases
> 45551 44 -rw------- 1 root root ? 43252 Jul 23 19:06 .bash_history
> 1213 4 -rw-r--r-- 1 root root ? 571 Apr 10 2021 .bashrc
> 
> NOTICE (time stamp in 24hr format 19:12:56)
> someUser:~$ date
> Wed Jul 23 07:12:56 PM PDT 2025
> 
> NOTICE last item of history 12
> 20250723T191303-0700 history 12
> 
> NOTICE
> the last modified time .bash_history file is 20250723T1906
> 
> I expected .bash_history file to be synced to time of last issued command 
> (i.e. 20250723T191303-0700)
> 
> WHAT IS THE RELATIONSHIP BETWEEN THE timestamp of the history command entries 
> and the last modified time of bash_history file for the given user?
> 
> Is this working as it should?

AIUI a bash session only writes to the history file when it quits.
That prevents commands from simultaneous but different instances of
bash getting interleaved.

You need to read the HISTORY section of man bash. That means scrolling
past a /lot/ of stuff about history. Search for HISTORY at the start
of the line.

Cheers,
David.