Today upon bringing up a bash terminal I tried finding a frequently-used command from my bash history via Ctrl-r. To my surprise, it wasn't found. Upon inspecting ~/.bash_history, I saw instances of the command on several lines. Does the command history not work by checking the file, either in real time or against a cached copy?
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2 Answers
It turns out there was a little more nuance than I was aware of: HISTFILESIZE determines the maximum number of lines saved in .bash_history, while HISTSIZE determines the number of lines from ~/.bash_history loaded into a searchable cache. Upon increasing HISTSIZE to match HISTFILESIZE, I was able to find the command via Ctrl-r.
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Thanks for posting this Q&A. I hope this clear demonstration of the interaction of these variables will help others too. Commented Sep 22, 2020 at 15:05
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It actually started as just a Q, but a few more minutes of digging yielded an answer! Commented Sep 22, 2020 at 15:08
Apart from this (HISTFILESIZE), there is one reason why a line won't appear in history: A leading space. If you start a command with a space in the front like this:
$ ls -l
$ ls -l (extra space at the beginning)
then the latter won't show up in history. Related, here is what my .bashrc looks like:
.bashrc:HISTCONTROL=ignoreboth
.bashrc:export HISTSIZE=100000
.bashrc:export HISTFILESIZE=100000
.bashrc:export HISTCONTROL=ignoredups:erasedups
.bashrc:export HISTTIMEFORMAT="%d/%m/%y %T "
HTH
