如何在 OS X El Capitan 中禁用 Bash 会话

Question

A seemingly new feature in OS X El Capitan (10.11 Beta) is Bash sessions (Terminal sessions) . I now have a ~/.bash_sessions directory with history files, and my HISTFILE and HISTIGNORE envars are being overridden. How can I disable all of this functionality?

Answer 1

If you startup a new Bash session manually (ie bash -xl ), you can see what is run on login.

You'll see the following line in the output:

....
+++ '[' '!' -e /Users/username/.bash_sessions_disable ']'

You can create a .bash_sessions_disable file in your home directory to disable this functionality.

Answer 2

This behavior is defined in /etc/bashrc_Apple_Terminal . It contains documentation comments describing what it does and how to customize it.

You can disable the per-terminal-session command history feature by setting SHELL_SESSION_HISTORY=0 in your ~/.bashrc script, as described here:

You may disable this behavior and share a single history by setting SHELL_SESSION_HISTORY to 0. There are some common user customizations that arrange to share new commands among running shells by manipulating the history at each prompt, and they typically include 'shopt -s histappend'; therefore, if the histappend shell option is enabled, per-session history is disabled by default. You may explicitly enable it by setting SHELL_SESSION_HISTORY to 1.

Note that, although you can disable the entire session-state restoration mechanism by creating ~/.bash_sessions_disable , this is unnecessary just to disable the per-session command history feature, and is not recommended.

Answer 3

To summarize, this has to do with Apple's Resume feature. When this feature is enabled, when you quit an app or reboot, the next time the app opens it will open the windows that were previously open.

With regard to Terminal, three things have to be in place for this to happen:

1. $HOME/.bash_sessions_disable must not be present
2. System Preferences/General/Close Windows when quitting an app must not be checked.
3. When rebooting, select Reopen windows .

When you reopen Terminal, it will reopen the same windows and tabs you had before in the same screen positions. Additionally, if you have checked Terminal/Preferences/your-window-type/Windows/Resume/Restore-text-when-reopening-windows , it will restore the text on each screen.

Finally, and this relates specifically to the OP's question, it will restore the history in each window/tab if the following conditions hold:

1. SHELL_SESSION_HISTORY is unset or set to 1
2. shopt histappend is not set
3. HISTTIMEFORMAT is not set

If SHELL_SESSION_HISTORY is explicitly set to 1 in .bashrc , the last two requirements are overridden, that is, shopt histappend or HISTTIMEFORMAT could be set.

Additionally, attention needs to be paid to the HISTSIZE and HISTFILESIZE variables. They should not be too large or too small, and some advise to leave them unset so they take Apple's default values.

Answer 4

Everything so far written about this subject is accurate and useful, and the techniques already mentioned should be used in lieu of this. I'm going to mention a totally nuclear approach, just for the sake of entertaining alternatives, and also to expand further understanding of this subject.

The only reason I acquired this knowledge is simply because I was looking for an alternative solution to needing to create a ~/.bash_sessions_disable file; I would have instead preferred preventing the sessions behaviour from happening by just adding some lines to my existing ~/.bash_profile . Unfortunately, that is not possible without going nuclear, so the official answer is still the best approach.

Summary

When Bash first starts up on MacOS, it will first source /etc/profile , which in turn sources /etc/bashrc . The contents of that file include this line:

[ -r "/etc/bashrc_$TERM_PROGRAM" ] && . "/etc/bashrc_$TERM_PROGRAM"

The $TERM_PROGRAM environment variable is only set by Apple's Terminal app. Printing the value of that variable returns Apple_Terminal . In other words, the /etc/bashrc file is attempting to source a /etc/bashrc_Apple_Terminal file if it both exists and is readable. It's in this file where MacOS does its special Bash session handling to tie into the Resume features of the OS.

After all that, Bash will then source any configurations a user has in their home directory (like ~/.bash_profile or ~/.bashrc ). This being stated, there's no way to override all the work done in the /etc/bashrc_Apple_Terminal file on a purely configuration level (vs both configuration and creating a new file) without doing what the others have mentioned, namely, setting $SHELL_SESSION_HISTORY to 0 to eliminate session-based history, and creating a ~/.bash_sessions_disable to prevent the .bash_sessions directory from being created every time Apple's Terminal is started.

Nuclear Approach

The two possible alternatives to eliminate any of this new MacOS functionality would be to either 1) remove that last line from the /etc/bashrc file, or 2) rename or delete the /etc/bashrc_Apple_Terminal to something else.

After doing this, Apple's Terminal app will no longer behave differently than non-Apple terminal emulators.