Finding an old command in the shell history

Question

How can I find an old command I ran in my terminal?

I used an appengine command and wish to just find it in my local command history without researching it online again.

Run history in terminal or if u remember some parts of the command history | grep <command-parts>, but note if you have made other commands and ure history settings in .bashrc is not large then you might never see it. — George Udosen, Mar 26 '17 at 15:56
Not sure it's worth a full answer... but you can also hit the ~/.bash_history file in your editor of choice ie: vim ~/.bash_history and search inside the file/editor. — WernerCD, Mar 27 '17 at 00:40

M. Becerra · Accepted Answer · 2017-03-26T20:40:48.270

27

History is what you are looking for.

Run history to get a list of the last 1000 commands, or run:

history | grep command_to_search

to search some pattern within the history generated list, for example:

history | grep apt

To search any apt related command, note that grep does not anchor your pattern to either end of the string, so no wildcards needed in most cases.

The history list is generated from the last 1000 commands (by default) stored in ~/.bash_history (which stores the last 2000 by default), and such file gets only updated whenever you exit your Bash session cleanly. That means, all commands from your current session will not be in that file until you close your terminal. They will also not be written if you kill the shell process.

Therefore, the command history (2000 last commands) can also be found at ~/.bash_history, by either:

less ~/.bash_history or, e.g. gedit ~/.bash_history
Opening Nautilus, Ctrl+h, and searching for the .bash_history file.

Both history and ~/.bash_history behavior can be changed by adding or modifying the options in ~/.bashrc, these are a few examples:

Append export HISTCONTROL=ignoreboth:erasedups or modify the existing HISTCONTROL line, to remove duplicate commands, i.e. if one runs echo Hello immediately after echo Hello, only one will appear in bash_history.
Modify HISTSIZE=1000 to extend or reduce the amount of commands shown with history
Modify HISTFILESIZE=2000 to extend or reduce the amount of commands stored in bash_history. Set HISTFILESIZE=-1 for unlimited.
Append HISTFILE=/path/to/file to save the history somewhere else.

Sources and further reading:

Bash man pages

Credit to comments from Byte Commander

edited Mar 26 '17 at 20:40

answered Mar 26 '17 at 15:59

M. Becerra

3,448

3

grep apt* does not what you think it does. First, the apt* will be processed by Bash's filename globbing, so if you have any files in your current directory that start with "apt", the glob will be replaced with them and grep would only search for those full filenames. To prevent globbing, wrap the pattern in double- or better single-quotes: grep 'apt*'. – Byte Commander Mar 26 '17 at 16:24
2

But this is still not what you want, because grep treats the pattern as regular expression, and in regular expressions, a * means "match the previous character any time, including zero" - so the pattern would match "ap", "apt", "aptt", "apttt" etc. You could write grep 'apt.*', because the . in a regular expression matches any character, but this is superfluous because grep does not anchor your pattern to either end of the string, so just write grep 'apt' and you will be good. – Byte Commander Mar 26 '17 at 16:26
2

Note also please that ~/.bash_history gets only updated whenever you exit your Bash session cleanly. That means, all commands from your current session will not be in that file until you close your terminal. They will also not be written if you kill the shell process. – Byte Commander Mar 26 '17 at 16:27
1

However, enough bashing for today. Your answer is nice other than those few points and I see you already started editing it to fix them. So have a +1 and hopefully you learned something today :) – Byte Commander Mar 26 '17 at 16:29
Yes I am learning indeed, thanks a lot for taking that time to explain. Just added the extra info :) – M. Becerra Mar 26 '17 at 16:53
@ByteCommander, re. grep apt* without any quotes, I made a small text file with the following strings, one per line: ap appointment appearance apt aptly aptitude aptness . Then I ran grep apt* on that file. The only hits were (one word per line): apt aptly aptitude aptness – DK Bose Mar 26 '17 at 17:28
@DKBose Could you possibly have had any file called apt in your current directory? – Byte Commander Mar 26 '17 at 18:36
Wow.. Tot I ask a simple question but am wow by the quality of answers.. And details about history and bash_history files.. Reverse search etc... Clearly written essays.. God bless you guys.. This has been the best responses I have ever received – saviour123 Mar 26 '17 at 20:30
@ByteCommander, yes! That was the name I gave that small file! I will try again with another name. – DK Bose Mar 26 '17 at 22:17
@ByteCommander, I did the same thing in an empty folder but this time calling the file test.txt and got exactly the results with grep apt*, 'grep apt*' and "grep apt*" as you predicted. Thanks! – DK Bose Mar 26 '17 at 22:24
It's not so much as "grep command_to_search" as it is "grep text_to_find" - it should search more than just "commands". history | grep zcvf will find tar -zcvf file.txt. You could also throw the ~/.bash_history file into an editor and find the commands that way. – WernerCD Mar 27 '17 at 00:32

Byte Commander · Answer 2 · 2017-03-26T21:45:44.973

There are many ways to find an recently executed command.

The most simple one is to just hit the ↑ key and cycle through your command history line by line until you spot what you looked for.
You can also press Ctrl+R to enter the so-called (reverse-i-search) mode.

It is a search prompt that will automatically complete what you start to type with the most recently run command that contains this string. When it shows what you looked for, press Enter to run it, or Esc to exit the search prompt while keeping the command on the prompt, so that you can edit it. To discard the result and exit search, hit Ctrl+C.
You can use the history Bash built-in to show the complete list of recorded commands from your history.

You can filter that list for lines matching a specific pattern using e.g. grep, like history | grep 'appengine'.

More info about the history built-in command of Bash can be found by typing help history.
Use bang-expansion to directly run the most recently executed command containing a string. This will replace the line you typed with the matching line from history and run it immediately, without confirmation, so be careful.

Simply type !string and it will replace that with the most recent command-line that started with "string".

If you want to run the last command that ended with "string", type !?string instead.

Or if you want the last command-line containing "string" anywhere, type !?string?.

More info about history bang expansion can be found by typing man history.

Wow.. Tot I ask a simple question but am wow by the quality of answers.. And details about history and bash_history files.. Reverse search etc... Clearly written essays.. God bless you guys.. This has been the best responses I have ever received — saviour123, Mar 26 '17 at 20:29

score 0 · Answer 3 · answered Mar 26 '17 at 15:59

0

If it was somewhat recently used it may be easy for you to find it by opening a terminal and using the up and down arrows on your keyboard to go through your last used commands.

answered Mar 26 '17 at 15:59

cP4n

275

Finding an old command in the shell history

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