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How To Use Bash History to Improve Your Command-Line Productivity

Whether you re new to the Linux command-line or you re a seasoned veteran,

these tricks will help turn your text-based meanderings into full-blown

marathons. Save time, speed up your productivity, and enhance your Linux-Fu,

all at once!

History Commands

The majority of these tricks utilize the history command in some way, so let

s cover that one first. Just type:

history

It s that simple! You ll output similar to the following:

To execute a specific command from your history, you can just type an

exclamation point followed by the number of the command as listed by history.

Here, I ll re-execute command number 510.

!510

By the way, an exclamation point is referred to colloquially as a bang.

You can also refer to a command by how long ago it was run. Next, let s execute

whatever we typed three commands ago.

!-3

Quick Substitutions

Let s say you want to rerun your previous command. Just type two exclamation

points. This is perfect for when you run a command that needs super-user

privileges and you forgot to do that. Just give it the old sudo bang bang

treatment:

sudo !!

Let s say you want to run a command with the last argument you used. Typing it

out is too tedious. Just use a bang dollar to substitute your last argument

automatically.

cd !$

What if you ran a command with two arguments and you want to run the first one?

Bang caret to the rescue! This works well when you make a backup of a config

file and then want to edit it.

nano !^

Next, let s search for a specific command from your history. Ctrl+R will search

backwards for whatever you type. It will autocomplete as you type, and you can

scroll through with the arrow keys to find the specific instance you re looking

for.

ctrl r

If you know the last command you ran with a specific keyword, you can skip the

search process and pare down your key presses by at least one.

!keyword

Now, for the power substitution: you can substitute an argument for your last

specific command using something similar to the previous method. Just add a

colon and the number of the argument.

ls !ln:2

Cleaning Up Your Tracks

If you want to clear your history, use this:

history c

And if you want to disable history altogether, use this:

HISTSIZE=0

To re-enable it, you can just change that value from 0 to something else (the

defaults are usually 500 or 1000).

But why should you choose between all or nothing? Use the following command to

make sure that any command that leads with a space does not get recorded in

your history.

HISTCONTROL=ignorespace

No Duplicates Here

I love using Bash s history. The one thing I don t like is duplicates. Use the

following command to ignore duplicate entries:

HISTCONTROL=ignoredups

If you want to use both ignorespace and ignoredups, you ll need to use

ignoreboth .

HISTCONTROL=ignoreboth

Pretend to Be Busy

As a bonus for you How-To Geek readers, I ll include the following, completely

irrelevant command:

cat /dev/urandom | hexdump -C | grep ca fe

This will continually generate random characters and values in a specific

format, which is nice to stare at for therapeutic reasons.

It also can come in handy in case you want to look busy or take a quick coffee

break at work. Don t be too responsible with this one, guys. ;-)

http://www.howtogeek.com/howto/44997/

how-to-use-bash-history-to-improve-your-command-line-productivity/