Ubuntu – Up arrow and .bash_history have different commands, so where does the up arrow get its data

bashhistory

I seem to have discovered that the ~/.bash_history file doesn't contain what is displayed when you use the up arrow. I found this by doing a command like so

smbclient -L 10.2.10.240 -umyuser -p"mypassword on the command line is bad"

This command is actually wrong, it has a mistake, the -u is actually supposed to be a -U and so this command failed.

However I also realized that that was bad to do, because it puts your password into the history, I went into .bash_history and what was interesting was that it doesn't have the mistake. It only has

smbclient -L 10.2.10.240

and that's it. But this is were it gets weird, if you use the up arrow the whole command including mistakes is there for you to edit.

So the question is, why is there a difference between what is in .bash_history and what the up arrow displays? Where does the up arrow data live?

Before you point it out; it's quite convenient in this case because it prevents my password from being saved, but, that's not why it's doing this, I also tested it with correct options and then it does save the whole command including passwords and all.

Best Answer

The ~/.bash_history file is only updated when you close/exit from the terminal. While you are in the terminal you can browse backwards in commands which was entered in that session. So if you exit from that terminal session your history will be updated with the missing command.

Also if you put a space at the beginning of a line, before the command, that command won't be saved in the history. This is a good practice if you issue a command which you don't want to be included in the history.

Related Solutions

Ubuntu – Bash history search, partial + up-arrow

Open your ~/.inputrc. If you don't have this file, see the end for how to create it. Add these lines:

## arrow up
"\e[A":history-search-backward
## arrow down
"\e[B":history-search-forward

Lines starting with # are comments. I can't remember what is backward and what forward. Experiment with it. Maybe you have to switch backward and forward.

Just re-open possibly open terminal windows for the new behaviour to become effective.

A bit background information:

Bash is using readline to handle the prompt. ~/.inputrc is the configuration file for readline. Note that this will also take effect in other software using the readline library, for example IPython.

Read the bash manual for more information about readline. There you can also find more history related readline commands.

To get the escape codes for the arrow keys you can do the following:

Start cat in a terminal (just cat, no further arguments).
Type keys on keyboard, you will get things like ^[[A for up arrow and ^[[B for down arrow.
Replace ^[ with \e.

For more information about ^[ and \e see here: https://unix.stackexchange.com/a/89817/380515

If you don't already have a ~/.inputrc file, copy the default settings over, or all the other default key bindings will be overridden:

cp /etc/inputrc ~/.inputrc

or begin your ~/.inputrc file with the following line

$include /etc/inputrc

[1]:

Ubuntu – Bash script and escaping special characters in password

Use double quotes twice, escaped and not escaped: -p"\"$MYPASSWORD\""

#!/bin/sh
source pass.cre
/usr/bin/ssh -p 91899 user@remoteHost 'mysqldump -u db_user -p"\"$MYPASSWORD\"" my_database |  gzip -c >  my_database.sql.gz'

Or an other version

/usr/bin/ssh -p 91899 user@remoteHost "mysqldump -u db_user -p\"'io#bc@14@9$#jf7AZlk99'\" my_database | gzip -c > my_database.sql.gz"

Examples

% source pass.cre
% ssh user@host mysqldump -u root -p$MYPASSWORD    
user@host's password: 
zsh:1: bad pattern: -p#8111*@uu(

% source pass.cre
% ssh user@host mysqldump -u root -p"$MYPASSWORD"   
user@host's password: 
zsh:1: bad pattern: -p#8111*@uu(

% source pass.cre
% ssh user@host mysqldump -u root -p"\"$MYPASSWORD\""
user@host's password: 
Warning: Using a password on the command line interface can be insecure.

Best Answer

Related Solutions

Ubuntu – Bash history search, partial + up-arrow

Ubuntu – Bash script and escaping special characters in password

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