Preserve tcsh history in multiple terminal windows

Question

How can we preserve or maintain the same history across multiple terminals?

The same question, but for bash shell , were discussed in the below link

Preserve bash history in multiple terminal windows

let me know the corresponding settings for tcsh shell ?

Answer 1

These variables set the history to merge itself instead of overwrite, and not save duplicates:

set history=1000
set histdup=erase
set savehist=(1000 merge)

the secret sauce is this line:

alias precmd 'history -S; history -M'

which will save and merge your history prior to printing the prompt - i.e. after each command you type.

all of the above should be added to your .tcshrc file.

Answer 2

In addition to Idan answer, I want to add that alias precmd 'history -S; history -M' potentially can mess up the history file, since it also records SIGINT and EOF signal (Ctrl+C and Ctrl+D).

A better way would be save and merge current shell history after running a command.

You can achieve it by this setup below instead, since the tcsh doesn't recognize SIGINT or EOF as a valid command.

alias postcmd       "history -S; history -M"

Answer 3

A single global history file is generally not what is desired, as it garbles command sequences when working on several tabs simultaneously.

If you want to keep your history PER TAB, use this approach:

set histfile=~/.history_`tty|sed "s#^.*/##"`
set history=1000
set savehist=(${history} merge)
alias postcmd 'history -S'

This will create individual history files for each tab, depending on their tty ID.

Using xfce4-terminal, if you do not change the order of tabs, and don't close tabs except the rightmost ones, this will correctly restore each history to its associated tab (and therefore, path). As re-ordering tabs takes the tty ID with them, but a xfwm4 session restore will re-create each tab from scratch (assigning new tty IDs starting from 0), it would restore the history files to the "wrong" tab (i.e., not the one with the directory path of their original tab). I haven't found a solution yet how to keep track of these changes.