Re: Ctrl+C during ~/.bashrc evaluation leads to unexpected behavior

[Chet Ramey]

On 3/17/25 3:26 PM, Ionut Nicula wrote:

Bash Version: 5.2
Patch Level: 15
Release Status: release

Description:
     Had this weird issue on my work laptop where my .bash_history file
would get truncated from time to
     time, and I had no idea what caused it because no background or
foreground process should modify
     .bash_history in that way.

     Turns out that this was caused by pressing Ctrl+C when ~/.bashrc
was being evaluated.

     Normally, on my PC, ~/.bashrc is very lightweight and I have a
very very small window when I can
     press Ctrl+C and have it aborted. But at work, the init takes
longer (~1 second) and I sometimes
     press Ctrl+C to abort it, run a command that doesn't depend on the
.bashrc init, and then close
     the shell. But this effectively sets the history length to 500
(the system default, instead of
     my actual infinite length in ~/.bashrc). When this happened
before, I didn't notice it right
     away. I only noticed like a couple of hours after I accidentally
truncated my bash history file,
     so I was very confused. It happened like 8 times in the last 12
months and it happened again
     today, so I decided to spend a bit of time on it and find the issue.

Repeat-By:
     1. Write a ~/.bashrc file that sets the history length to allow
infinite number of entries.
     2. Write a global bash config that sets the history length limit to 500.
     3. Add 1000 lines to the bash history file.
     4. Add a command like 'sleep 999' to your ~/.bashrc before the
lines that set up the infinite
        history size, in order to simulate a slow initialization.
     5. Start a new bash instance, press Ctrl+C, and notice how
.bash_history gets truncated to 500
        lines.

It's fairly straightforward: if you interrupt startup file execution before
setting important variables, those variables aren't set and, in some cases,
receive default values.

Fix:
     I'm not sure what tweaks are 'allowed' here, but ideally, I would
like some kind of flag that
     simply closes the bash instance if I ever press Ctrl+C during
.bashrc evaluation because, as my
     report demonstrates, it can quite easily lead to weird and

confusing behavior.

If you want this, set a trap on SIGINT in your .bashrc that exits the
shell. You can reset the trap to the default as the last command in
your .bashrc.


--
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    c...@case.edu    http://tiswww.cwru.edu/~chet/

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