bash history grep alias

In a previous post, I introduced many useful bash shell aliases that I use. There's one that I've made a notable improvement to that I'd like to share. If you spend a lot of time on the command-line and use bash, you should really try this out.

'bhg', for "bash history grep," was a pretty simple alias to search through your bash history file. Previously, I used it like this:

alias bhg='cat $HISTFILE | grep'

The deficiency I found with it is that I often keep a shell open for days (even weeks!) at a time. So, I may be searching for a command that has not been written to the history file. What I'd like, then, is one 'bhg' alias that will find any command from my current shell history or my history file. The bash 'history' built-in will give you all of the current shell's command history. We just need to strip out the line numbers -- easy enough with 'sed' -- and then con-'cat'-enate that with the history file and we're in business. So, this is what I use now to accomplish all that:

alias bhg="history | sed 's/^ *[0-9]* *//' | cat $HISTFILE - | grep "

As I mentioned before, if you find this useful, you can make it even more useful by increasing the history size variables in your ".bash_profile". Namely, 'HISTSIZE', which controls how many lines of current history will be available via the history command, and 'HISTFILESIZE', which controls how many lines of command history will be written to your history file. They both default to 500, I think, which I've found to be way too small for my purposes.