I'm running KSH on RHEL 2.6 on x86. KSH version is:
sh (AT&T Research) 93u+ 2012-08-01
Switching to Bash or back to Tcsh (which I happily used at my old job) is not possible.
The first annoying thing I noticed about KSH is that sometimes my history from different terminals (I have many terminals open at a time) got mixed together when scrolling through history with the up key. I then learned that there's a single HISTFILE shared by all my terminals. Fine, but still weird that they weren't always getting intermixed. I also noticed the HISTFILE wasn't always updated immediately. Eventually I decided that KSH was probably buffering some command history and periodically flushing the contents to HISTFILE. I couldn't find that behavior documented anywhere but it seems like a reasonable explanation.
I really want different history for each session, so I added this to my .kshrc file:
HISTFILE=~/.hist.$(tty | sed 's;.*/;;')
which is supposed to give a unique HISTFILE per terminal. It does that, which is great. But...these HISTFILES seem to periodically get cleared. Most of mine have a file size of 0 bytes right now.
Update: The individual HISTFILEs for all my open terminals are being cleared every 10 minutes. Like clockwork.
Anybody seen this before???
Update: Two years later and I am still no closer to an answer. It's been particularly annoying lately. Started poking around the ksh source but I'm a hardware designer and there aren't a lot of comments so this is pretty tough.
Well maybe this is a clue. Every line in my history files starts with a ^@ character (as rendered by emacs). I think that means 0x40 (@ character) + 0x80 (for the control bit) = 0xc0 = octal 300. The only special characters mentioned in history.c, as far as I can tell, are 0201 and 0202. My history files do start with \201 (again, as rendered by emacs, I guess this is octal).
Here's a sample of a typical history file, does this seem normal:
�ls pwd clear ls ls ttyHmm those control characters don't display correctly. Transcribed as regular characters it looks like:
\201^Als^@pwd^@^@clear^@^@ls^@ls^@tty^@^@Sometimes I get two of those ^@ characters and sometimes one, and I can't figure out why. This might not be a clue but I have no other leads right now.
UPDATE: SOLVED! Well almost. No sooner did I post that then I started searching for some other things in history.c. I saw this:
/* * clean out history file OK if not modified in HIST_RECENT seconds */static int hist_clean(int fd){ struct stat statb; return(fstat(fd,&statb)>=0 && (time((time_t*)0)-statb.st_mtime) >= HIST_RECENT);}and no surprise here, HIST_RECENT is set to 600, exactly the 10 minute interval I was looking for. I haven't quite figured out how to disable this yet, but it sure seems like intentional behavior, no matter how much I hate it.
