Using Bash History More Efficiently

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If you've used bash for a while you probably know that the commands you enter are saved in the file ~/.bash_history when you log out. Next time you log in, bash automatically loads these history commands from the saved file and you can then use the up and down arrow keys to browse your command history and find the command you want rather than re-entering it.

However, there are more effective ways to use bash's history: you can use Ctrl+R (Control key held down at the same time as the R key). This will display the following in your shell:

(reverse-i-search)`':

If you know type some substring found in the command you're searching for, for example "ls", bash will search for matching commands. For example, it might show:

(reverse-i-search)`ls': lsof -nP -p 3930

What it actually shows is going to be dependent on the commands you've previously entered.

When you do this, bash looks for the last command that you entered that contains the substring "ls", in my case that was "lsof ...". If the command that bash finds is what you're looking for, just hit Enter to execute it. You can also edit the command to suit your current needs before executing it (use the left and right arrow keys to move through it). If you're looking for a different command, hit Ctrl+R again to find a matching command further back in the command history. You can also continue to type a longer substring to refine the search, since searching is incremental.

Note that the substring you enter is searched for throughout the command, not just at the beginning of the command.

______________________

Cheng Renquan, Shenzhen, China

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UNIX/Linux

John Barry's picture

more . bash_history

hs example caveats

Anonymous's picture

The example find/rm commands are not bullet proof
if file names e.g. contain spaces. find and xargs
as well as the other alternative have ways of dealing
with that, so "man find" and "man xargs" ;-)

I wasn't suggesting the find/rm examples as models for best practice.
But defining an hs function can be handy, and you can put it
in an appropriate bash initialization file to have it available
automatically if you like.

BTW, this
http://tldp.org/LDP/abs/html/
link leads to a lot of good bash tips.

In bash, the history command

Anonymous's picture

In bash, the history command will list
the whole recorded history to stdout, so you can easily
pipe that to grep and search for an arbitrary pattern.

To make that more handy, you can define a function, e.g.,
hs (for history search, hg already existed for me ;-) thus:

[15:33 ~]$ function hs () { history|grep "$@" ; } # don't leave out spaces

Then, if you remember some complex command, e.g., involving
find and rm, you can do something like

[15:33 ~]$ hs 'find.*rm'
225 find .. -type f -iname '*swp' |xargs rm -iv {} \;
228 for f in $(find .. -type f -iname '*swp'); do rm -iv $f;done
533 hs 'find.*rm'

Hm, that command 228 was safer than 225. I remember using echo to
pre-test the action. Look for that:

[15:34 ~]$ hs 'find.*echo'
227 for f in $(find .. -type f -iname '*swp'); do echo "'$f'";done
534 hs 'find.*echo'
[15:34 ~]$

It pays to pay attention to detail if re-executing with !nnn
e.g. the find above was below the parent directory at the time. It
won't be what you want to repeat from another place, most likely.

Your history will obviously yield different matches from mine.
BTW, do not arbitrarily remove .swp files!! They are vim's way
of protecting you from yourself ;-) Don't mess with them unless you
know for sure they are no longer needed! I only used that example
because most other commands in my history are trivial to retype.

In my humble opinion, there's only <C-R> useful.

Cheng Renquan's picture

In my humble opinion, there's only most useful.

Other commands like "!tail" starts with "!" are not useful just because I don't trust them only if I see and confirm the whole command. Commands like "!tail" are harmless that it never will destory something, but do you dare to execute "!rm" ? Do you know what will be removed if you don't remember the whole command?

Commands like "!tail:p" are also not very useful that it needs more key strokes. I use and "tail" to check the last commands contains "tail", it needs less key strokes.

Setup extra key bindings in ~/.bash_profile is really useful, for those want to customize something, I just only use the default Bourne-again shell.

Cheng Renquan, Shenzhen, China

Onw nice tip is to use

Anonymous's picture

Onw nice tip is to use Up/Down arrows for forward/backward history search:
# a better up/down arrow key behaviour
bind '"\e[A"':history-search-backward
bind '"\e[B"':history-search-forward

Now start typing a command (say - ssh) and hit Up arrow to search for all ssh commands.

Regarding history search with "!".

On July 8th, 2009 Anonymous
# !tail:p

One could:
$ !tail Alt+^
which would complete the !tail command (in cases when you are not sure).

Great stuff

statmonkey's picture

Thanks for the main article and the great comments. That is so cool.

Additional tip

Douglas Potts's picture

Set up the following bindings in your .bashrc or .bash_profile:

# Setup and to act like vi for command line history searching
bind -m vi-insert \C-f:history-search-forward
bind -m vi-insert \C-b:history-search-backward

This allows for Control-B to search back through your history for lines matching the partial command you have already typed. Example:
$ history |tail -10
201 svn checkout -r 5267 .
202 svn update -r 5267
203 ls
204 cd build/
205 ls
206 doxygen Doxyfile 2>&1 | tee doxygen_R5267.log
207 grep c-b ~/.bash*
208 more ~/.bashrc
209 hist |last -10
210 history |tail -10
$ doxy
$ doxygen Doxyfile 2>&1 | tee doxygen_R5267.log

One limitation, it is for Vi-keybinding types.

save time searching through bash history

Anonymous's picture

Good tip. I guess what I'm about to share is also related to this article and most importantly saves you a bit of time when combing through your bash history. In order to execute a command you used before, you can just enter an exclamation mark "!" before the command and it'll be executed.For instance if I ran the command 'tail -n 100' and I wanted to execute it again, instead of typing the whole command, i can just do:

# !tail

and my previous command will be executed. In some cases, you might just want to see the command but not execute it. Then you can do:

# !tail:p

Hope this is useful to someone.

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