Command line tips & tricks

PrzemoF · 16-04-2013 10:41am #1

"1. Use "!"

If you use the command line a lot, it is very likely that you will run several different commands in a short span of time. And if you want to re-run a command that was just recently used, using "!" is much faster than using the arrow keys to find the command. With "!", you only have to remember the name of the command. For example, if you want to re run the last "vim" command, you just need to typ "!vim" and vim will open the last file without you typing the whole command.

2. Use "!!"

Using "!!" is the best way to re-call the previous command. It is actually faster than using the arrow keys. For example, when you forget to type "sudo" before the previous command, to re-run it with sudo, you just need to type "sudo !!"."

More here: http://www.linuxandlife.com/2013/04/some-tips-to-use-command-line-faster.html

mickgotsick · 16-04-2013 10:55am

1. Use "!"

You can use "!" with the history command as well. For example, you can search your history for a command of interest: history | grep <command>

Each of the results will be numbered and to re-execute the one you want, you can just do !<number>

Khannie · 16-04-2013 11:18am

My favourite is ctrl+r. It searches back through your history for commands containing whatever string you type.

e.g. ctrl+r, then type vim will bring up your last command containing vim, ctrl+r again and it'll find the one before that, etc.

Tree · 16-04-2013 12:29pm

Ctrl+r is probably the most useful way to root through my history.
The other thing I do is alias the crap out of things I do regularly, using capital letters for the beginning of them helps narrow down the tab-complete a lot

Khannie · 16-04-2013 3:44pm

Oh, the other thing I use all the time is !$ which means "the last argument in the last command line"

So, for example:
vim /long/path/to/file.txt
mv !$ /tmp

will mv file.txt to /tmp

or even better....

mv !$ !$.bak also works

OOOH! Tasty!

Khannie · 16-04-2013 4:02pm

I'm spamming now, but these are things that I'm just coming across during a day....

If you have done key exchange on a remote server, tab completion does work.

e.g.

scp file.txt user@remote_server:~/dir<tab> will fill in the rest of the directory name for you. Obviously only works well on a LAN, but can be OK over the internet in a pinch.

Hotblack Desiato · 17-04-2013 2:38am

Khannie wrote: »

Oh, the other thing I use all the time is !$ which means "the last argument in the last command line"

Or alt-dot which pastes the last argument in, and it can be edited.

mv !$ !$.bak also works

OOOH! Tasty!

That's a good one alright

Khannie · 17-04-2013 10:02am

ninja900 wrote: »

Or alt-dot which pastes the last argument in, and it can be edited.

Beauty! That's a good one. Cheers.

PrzemoF · 17-04-2013 12:28pm

^abc^def Run previous command, replacing abc with def

Ctrl-XX toggles between current position and the beginning of the line

Ctrl-A moves cursor to the beginning of the line

Some more tips here: http://ss64.com/bash/syntax-keyboard.html

mickgotsick · 17-04-2013 1:40pm

PrzemoF wrote: »

^abc^def Run previous command, replacing abc with def

Ctrl-XX toggles between current position and the beginning of the line

Ctrl-A moves cursor to the beginning of the line

Some more tips here: http://ss64.com/bash/syntax-keyboard.html

Ctrl-E moves the cursor to the end of the line.

syklops · 18-04-2013 10:47am

There are some real gems here.

I just used !$ for adding an account, e.g.:

useradd username01
passwd !$

Very handy. I will be using this alot!

mickgotsick · 18-04-2013 11:00am

One thing that took me a while to discover was how to match a tab character using the standard grep command. It's easy to do with a perl one liner (or with one of the grep variants?) but if you want to use the standard grep you can use :space: to match a tab (also matches spaces though).

[-0-] · 18-04-2013 1:48pm

Can we please sticky this thread? It's very useful.

I love brace expansion:

vi /etc/httpd.conf

cp !${,.bak}

diff /etc/httpd.conf{.bak,}

GreenWolfe · 18-04-2013 3:14pm

Some really handy cd tricks here:

http://www.thegeekstuff.com/2008/10/6-awesome-linux-cd-command-hacks-productivity-tip3-for-geeks/

I really like this one for going up multiple directory levels with cd:

alias cd..="cd .."
alias cd...="cd ../.."
alias cd....="cd ../../.."
alias cd.....="cd ../../../.."
alias cd......="cd ../../../../.."

# cd /tmp/very/long/directory/structure/that/is/too/deep
# cd.....
[Note: use cd..... to go up 4 directory level]
# pwd
/tmp/very/long/directory/structure

syklops · 18-04-2013 4:23pm

I was going to ask this question:

Does anyone know a way to move the cursor back one position, aside from using the arrow key?

I ask, because in the brace expansion example, I would type that as cp !$ {}, then left arrow so I am between the braces and then type ,.bak. The reason being that I can do the {} in one movement and keep my hands in the same position, but I have to move my right hand off the keyboard to hit the arrow key, which is annoying and slows me down(albeit by less than a second, but time is money people!).

But, with a little trial and error I found the answer myself. The answer is CTRL + b.

Now to type the above example, I type !$ {} CTRL + b ,.bak ENTER

Confused yet?

Khannie · 18-04-2013 4:48pm

[-0-] wrote: »

I love brace expansion

Oh yes. Love that!

for i in {0..9}; do <something 10 times>; done

for i in {0..9}{0..9}; do <something 100 times, starting with 00, 01, etc.>; done

[-0-] wrote: »

Can we please sticky this thread?

There is no mod of this forum. We're all to peaceful to require moderation.

[-0-] · 18-04-2013 4:53pm

Khannie wrote: »

Oh yes. Love that!

for i in {0..9}; do <something 10 times>; done

for i in {0..9}{0..9}; do <something 100 times, starting with 00, 01, etc.>; done

These always save me from having to fire up python.

Love it!

There is no mod of this forum. We're all to peaceful to require moderation.

Shame on us then! :P It might be worth dropping the cat mod a PM.

Hotblack Desiato · 18-04-2013 9:33pm

EarthlyPangaea wrote: »

Some really handy cd tricks here:

alias cd...="cd ../.."
alias cd....="cd ../../.."

Or - openSUSE has these built in:

alias ..='cd ..'
alias ...='cd ../..'

Also a good built-in one is

alias ll='ls -l'

I've added one to get rid of Flash cookies.

alias killflash='rm -rf ~/.adobe ~/.macromedia'

syklops · 19-04-2013 9:37am

ninja900 wrote: »
Or - openSUSE has these built in:
alias ..='cd ..'
alias ...='cd ../..'
Also a good built-in one is
alias ll='ls -l'
I've added one to get rid of Flash cookies.
alias killflash='rm -rf ~/.adobe ~/.macromedia'

I used to use ll alot, and then I was on a system(can't remember which one) and it didn't have it, and I got out of the habit of using it. Just tried it now and Fedora has it.

19-04-2013 2:19pm

Prevent disasters, asks for a prompt to delete

alias rm='rm -i'

Not many know this one.. Override the alias!

\rm

This will ignore the alias above!

syklops · 19-04-2013 5:39pm

Shiloh Echoing Tigress wrote: »
Prevent disasters, asks for a prompt to delete
alias rm='rm -i'
Not many know this one.. Override the alias!
\rm
This will ignore the alias above!

On mission critical systems I go one further and I do:

alias rm='mv --target-directory /tmp/garbage

with a cronjob which periodically deletes the contents of the garbage directory.

Saved my ass a few times.

There was a bug in bash a while back where tab complete didnt append the '/', instead completed the word and added a space. I don't need to tell you what happened when I meant to do ' rm /bin/somedir/*' and instead did 'rm /bin/somedir *'

Ant · 20-04-2013 3:51pm

Many of the bash shell's best features have already been mentioned in this thread but one of my favourites is:

set -o vi

I used to be reasonably nifty with the default Emacs key bindings but, as a vim user, my command line editing has been much faster since I started using the vi key bindings.

More recently, I've also added

shopt -s histreedit

to my bashrc. This provides the opportunity to re-edit bash history substitutions that didn't work the first time (which happens often enough for me).

It's worth having a read of the bash manual every so often and experimenting with features you didn't know about or haven't previously tried.

PrzemoF · 01-05-2013 9:54am

Rename all htm files to html:

rename .htm .html *.htm

or

rename all files containing strange_file_name to image:

rename strange_file_name image strange_file_name*

i.e.
strange_file_name_001.jpg -> image_001.jpg
strange_file_name_002.jpg -> image_002.jpg

I noticed that it's quite common to rename files using some one line bash scripts, but that's the easiest way.

Ant · 06-05-2013 1:18pm

PrzemoF wrote: »
Rename all htm files to html:
rename .htm .html *.htm

This is indeed a very useful command - and one I've used many times. It's worth mentioning that the rename program described by PrzemoF is the one from the util-linux package which usually forms part of the stock install of Red Hat derived distributions.

However, in Debian-based distributions (including Ubuntu and Mint) rename is sym-linked to a Perl script povided by the perl package. This script similarly allows the user to rename multiple files but it works differently: it's basically a wrapper to modify multiple file names using the same Perl expression. e.g. the above use case would be implemented as:

rename s/htm/html/ *.htm

An advantage with the Perl version is that it's more flexible. Also, it doesn't silently over-write files if a file with the same destination name already exists - which once happened to me.

Khannie · 13-05-2013 4:57pm

Got a good one today - let's say you've kicked off a long running process and now you want to shift it to a screen session instead of killing it.

(as root)
echo 0 > /proc/sys/kernel/yama/ptrace_scope

(as yourself)
screen
reptyr <pid>

bingo, bango!

Hotblack Desiato · 13-05-2013 11:39pm

Hmm was stumped there for a minute until I did a search, Yama only came in with 3.4 kernel and I'm still on 3.1

will have to upgrade soon anyway though!

KAGY · 14-05-2013 8:49am

Been using the find command a lot recently. Esp with the exec option

find ./ -type f -exec sudo chmod -c 640 {} \;
For when I need to change perms for files only recursively
Or using it with mplayer over ssh from my phone to the htpc to play music without turning the screen on . (Scared the skit out of the OH from work accidently running that)

Khannie · 14-05-2013 9:46am

ninja900 wrote: »

Hmm was stumped there for a minute until I did a search, Yama only came in with 3.4 kernel and I'm still on 3.1 will have to upgrade soon anyway though!

It may just work without that config change on older kernels. Worth a whirl anyway.

syklops · 14-05-2013 11:00am

KAGY wrote: »

Or using it with mplayer over ssh from my phone to the htpc to play music without turning the screen on . (Scared the skit out of the OH from work accidently running that)

Sh!t like this is why I love Linux.

PrzemoF · 21-05-2013 9:34am

Copy/move all files (filtered) from subdirectories to a new directory:

Real life example - I had to copy all gnome icons containing word 'symbolic' to a new directory. The directory symbolic was already existing.

find . -type f -name '*symbolic*' | xargs -I {} cp {} symbolic

And more generic:

find [any-find-options] | xargs -I {} cp {} /any/directory/you/want
find [any-find-options] | xargs -I {} mv {} /any/directory/you/want

Khannie · 21-05-2013 10:31am

Handy. FYI - find has an exec option, so:

find <stuff> -exec cp {} <destination> \;

I regularly use it to grep stuff in a large set of files / directory tree:

find <stuff> -exec grep --with-filename <pattern> {} \;

Command line tips & tricks

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