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Re: PROMPT_COMMAND='history -a; history -n' causes shell hang in OX 10.1


From: Graham Jones
Subject: Re: PROMPT_COMMAND='history -a; history -n' causes shell hang in OX 10.10 Yosemite / bash 3.2.53
Date: Wed, 5 Nov 2014 08:44:32 +1100

> On 5 Nov 2014, at 12:54 am, Chet Ramey <address@hidden> wrote:
> 
> On 11/3/14 5:08 PM, Graham Jones wrote:
>> These are for:
>> bash --version
>> GNU bash, version 4.3.30(1)-release (x86_64-apple-darwin14.0.0)
> 
> This trace looks pretty reasonable.  Maybe you could temporarily move your
> history file to some other name and see if you can reproduce this behavior
> starting fresh with an empty history file.
As you may have seen from the other email, the history file is relatively 
small. 
I did just remove it and start afresh, and the issue still occurs. 
Whilst attempting to reproduce it, I noticed that is doesn’t reoccur 
immediately. 
In my first test, I deleted the history file and closing that session (the only 
one). When I created a single terminal session, I could su to root and hit 
return a large number of times without it reproducing the error. I need created 
another terminal session and (without suing) after issue just a single command, 
the next command on the root terminal exhibited the behaviour.
I retried a similar experiment, again after removing the history file, and 
again it wasn’t immediately reproducible. This time I didn’t create a second 
session but left the terminal along for 3 or 4 minutes. When I next entered a 
command the behaviour has returned. 
In both cases the line count in $HISTFILE was low = ~40.

Now after performing these to experiments I just tried to create a new session 
and found my $HISTFILE owned by root (or at least permission denied, I didn’t 
actually check the file mode and owner before chmoding it). This seems strange 
given I never log in as root only su so presumably the first command executed 
must always be by my own user. 

After chmoding it, I notice this:
address@hidden:~$ wc -l $HISTFILE
  500001 /Users/graham/.bash_history

I have obviously not entered that many commands!

Immediately after I go to check the contents and it’s owned by root again
address@hidden:~$ wc -l $HISTFILE
wc: /Users/graham/.bash_history: open: Permission denied
address@hidden:~$ l $HISTFILE
-rw-------  1 root  staff  1500000  4 Nov 21:36 /Users/graham/.bash_history
address@hidden:~$ ps aux |grep bash
graham          99600   0.0  0.0  2432772    648 s000  S+    9:40pm   0:00.00 
grep bash
graham          99555   0.0  0.5  2492596  39076 s000  S     9:36pm   0:00.49 
-bash

But yet there is only my bash running non-priveledge. 

Now I was expecting a hole in the file, but when I finally get to see the 
contents, I have 500,000 ls commands in there (one of my test commands from 
above)
address@hidden:~$ wc -l $HISTFILE
wc: /Users/graham/.bash_history: open: Permission denied
address@hidden:~$ sudo chown graham $HISTFILE
Password:
address@hidden:~$ sort $HISTFILE | uniq -c | sort -n
   1 sudo chown graham $HISTFILE
   1 vi $HISTFILE
500000 ls


> 
> Chet
> 
> -- 
> ``The lyf so short, the craft so long to lerne.'' - Chaucer
>                ``Ars longa, vita brevis'' - Hippocrates
> Chet Ramey, ITS, CWRU    address@hidden    http://cnswww.cns.cwru.edu/~chet/



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