Re: Common History across Shell

On Jul 10, 1:36 pm, quarkLore <agarwal.prat...@xxxxxxxxx> wrote:
AFAIK history in bash is implemented such that each bash instance
maintains its individual history in memory. As and when a bash session
exits it updates history file.

If there are multiple shells running together then commands entered in
one can't be accessed using history command from other shells.

I am looking for a feature where if a user has multiple shells and on
a special keystroke / command all shells get a common history which is
sum of all histories.

Does such a feature exist in bash or any other shell?
Can such a feature be implemented without changing the shell's code?

Yes. That is precisely what bash appears to be doing. .bash_history is
opened in read only mode and appends the commands to the file when
bash exits.

[root@braveheart]# truss -t open bash
open("/var/ld/ld.config", O_RDONLY) Err#2 ENOENT
open("/lib/libcurses.so.1", O_RDONLY) = 3
open("/lib/libsocket.so.1", O_RDONLY) = 3
open("/lib/libnsl.so.1", O_RDONLY) = 3
open("/lib/libdl.so.1", O_RDONLY) = 3
open("/lib/libc.so.1", O_RDONLY) = 3
open64("/dev/tty", O_RDWR|O_NONBLOCK) = 3
open("/proc/2546/psinfo", O_RDONLY) = 3
open64("/var/run/name_service_door", O_RDONLY) = 3
open64("/root/.bashrc", O_RDONLY) = 4
open64("/root/.bash_profile", O_RDONLY) = 4

open("/usr/share/lib/terminfo//x/xterm", O_RDONLY) = 4
open64("/root/.bash_history", O_RDONLY) = 4
open64("/root/.bash_history", O_RDONLY) = 4

open("/usr/share/lib/terminfo//x/xterm", O_RDONLY) = 4
[root@braveheart]# exit
exit
open64("/root/.bash_history", O_WRONLY|O_APPEND) = 4
open64("/root/.bash_history", O_RDONLY) = 4
open64("/root/.bash_history", O_WRONLY|O_TRUNC) = 4
[root@braveheart]#

There is no syncing of bash_history that happens if you have multiple
shells which are run by same user. I have verified that

.

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