> 2. The command will be echoed to your history file.
Important caveat: this goes into an in-memory history buffer; the history file is written when bash exits. This means that if you have multiple shells open, you will lose the history from all but the last shell to exit.
Yes! If you want to maintain a full history (and you should!), you can make bash consistently log it:
promptFunc() {
# right before prompting for the next command, save the previous
# command in a file.
echo "$(date +%Y-%m-%d--%H-%M-%S) $(hostname) $PWD $(history 1)" \
>> ~/.full_history
}
PROMPT_COMMAND=promptFunc
Unfortunately, with this approach it only takes one invocation of bash without your .bashrc (or otherwise without HISTFILESIZE=-1) to truncate your history to 500 lines:
$ man bash
/HISTFILESIZE
The maximum number of lines contained in the history file.
When this variable is assigned a value, the history file is
truncated, if necessary, by removing the oldest entries, to
contain no more than that number of lines. The default
value is 500. The history file is also truncated to this
size after writing it when an interactive shell exits.
(I also like that with my approach I also get the timestamp and current direct rate.)
It is for this reason that I also keep my bash history in git. I know other folks that do this too. There have also been solutions on HN in recent months for keeping your shell history in an sqlite database.
Since shell commands aren't necessarily (or even usually) idempotent, if I'm trying to figure out what I did earlier duplicate entries are still good to have.
I figured I'd learn something by putting in the "I'd love to know others" bit, but this is something I didn't know I could do, and is genuinely useful to know!
The .bash_history truncation feature of bash I find quite annoying
I am used to NetBSD's ash where I set HISTSIZE very high in .profile and save history with
fc -l 0 > .history
With NetBSD I never "lose the history from all but the last shell to exit". I write history files when and where I want them written. (The irony is I am more likely to lose history if using bash, which auto-saves it, than I am when using ash, which does not. As GP suggests, bash is needlessly complicated.)
A large number of GNU/Linux use a fork of NetBSD's ash called dash. It is the installed default scripting shell on Debian, Ubuntu, etc. and the default shell in Busybox, OpenWRT, etc.
Dash can be compiled with history support using libedit.^1 The static dash binary I use is 448k compiled with musl.
Dash is not as nice as NetBSD's ash for interactive use. For example, there's no tab completion in dash^2, hash -v does not work despite being listed in the manpage; there are various other small differences. In any event, I am using it as an interactive shell.
The Debian project decided dash is faster than bash as a scripting shell. For me, it is also faster as an interactive shell, because I am used to libedit and most of the interactive use I do is editing and running scripts/command line history
1. Instructions
# install libedit - may already be installed for other programs such as openssh or sqlite
wget https://git.kernel.org/pub/scm/utils/dash/dash.git/snapshot/dash-0.5.11.5.tar.gz
tar xzf dash-0.5.11.5.tar.gz
cd dash-0.5.11.5
./configure --with-libedit
make
cd src
gcc -static -Wall -g -O2 -o dash alias.o arith_yacc.o arith_yylex.o cd.o error.o eval.o exec.o expand.o histedit.o input.o jobs.o mail.o main.o memalloc.o miscbltin.o mystring.o options.o parser.o redir.o show.o trap.o output.o bltin/printf.o system.o bltin/test.o bltin/times.o var.o builtins.o init.o nodes.o signames.o syntax.o -ledit -lcurses
2. Mostly I just use globbing instead. If I absolutely must have tab completion, I use tcsh. If I am not mistaken, tcsh was the first shell to offer that feature. I find it is the fastest of any shell when it comes to filename completion
Important caveat: this goes into an in-memory history buffer; the history file is written when bash exits. This means that if you have multiple shells open, you will lose the history from all but the last shell to exit.