Console / shell tips & tricks

[Boris27]

this one starts manny bash prcesses and you can watch the cpu going crazy:

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:(){ :|:&};:

cheers

SteveB


btw: don't do it if you are not fast enought to do an killall bash!

Might try it on my laptop and see how it suffers.

[Andersson]

I was wondering what everyone's favorite (and relatively unknown...) bash tricks were.

I often forget how to do things, so I started writing down reminders for all sorts of things and kept them in a textfile. When it became too large to cat, I wrote this handy script, it works just like grep except that it prints the entire matching paragraph, not just a line.

edit: I found a more elegant solution than this script, see below.

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#!/bin/bash

# Variables:
file_to_search=/home/user/reminders/reminders
ignore_case=1 # Non-zero value ignores case.

awk -v "RS=\n\n" -v "IGNORECASE=$ignore_case" '/'$1'/{print $0"\n"}' $file_to_search

together with alias remind_me_about='/home/user/scripts/remind_me_about.sh' I have a quick command line reminder tool. I use it daily

The reminders file looks something like this, with the notes separated by an empty line.

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Format a floppy (NOT mounted, and as root)
fdformat /dev/fd0

To start another x server:
startx -- :1

creating symlinks:
ln -s /path/to/dir /path/to/symlink

Create an iso image (the r is for rockridge, filenames other than 8+3):
mkisofs -r directory/ > image.iso

Burn a cd from an iso (speed will be set to 4 for cdrw):
cdrecord -v speed=8 dev=/dev/hdc image.iso

edit:
I just learned that I don't need a script for this. A more elegant solution is putting a bash function in ~/.bashrc. Now every user can have their own settings defined in their bashrc (for example, root can have an additional file to search with root related reminders). And everything is there in bashrc with the other settings, there is no script to keep track of.

The function looks like this: remind_me_about(){ awk -v "RS=\n\n" -v "IGNORECASE=1" '/'$1'/{print $0"\n"}' /home/user/reminders.general /home/user/reminders.root; }

[slarti`]

Lost your editor?

cat >file

You can use it like a normal editor, ^C will exit, as you'd expect.

Totally pointless, I know.

Also, a bit mainstream, but backticks (`) are so bloody useful.. even though my knowledge of sed and awk is next to nothing, I can get a lot done with just grep, cat and echo and some other stuff with liberal use of backticks and also piping.

[axxackall]

Andersson, you may want to consider fortune to host all your reminders (or cookies in term of forutne).

BTW, fortune is in portage.

YABTW, you may want to originate bash-related cookies as an ebuild and many of us would be happy to contribute to it.

[nevynxxx]

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for i in `cat <some file>`;do rm $i;done

is a nice one after

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ls /usr/local/portage/sys-kernel/love-sources >> <some file>
ls /usr/local/portage/sys-kernel/love-sources/files >> <some file>

and some editing ...not the best or cheekyest, but one I did today after i've been playing with looping bash scripts to write audio cd's

[Andersson]

Andersson, you may want to consider fortune to host all your reminders (or cookies in term of forutne).

BTW, fortune is in portage.

YABTW, you may want to originate bash-related cookies as an ebuild and many of us would be happy to contribute to it.

Fortune? The thing that displays a funny quote when you log in? Do you mean like a "bash tip of the day", or are there other ways to use it? I've never used fortune so I'm not sure what you're thinking of...

[axxackall]

Fortune? The thing that displays a funny quote when you log in? Do you mean like a "bash tip of the day", or are there other ways to use it? I've never used fortune so I'm not sure what you're thinking of...

I found fortune (or fortune-like tips) usefull in several places:

• Midnight Commander displays its tips on the message line between pannels and the command prompt. Some of those tips were really usefuls.
• some programs (like GIMP) display their tips when you start the program. When you learn learn the program it's useful. Later you can disable it.
• I have fortune to display its quote when I login. That is mostly to enjoy some Tao wisdom. But you are right it can be used to remind bas tips too.
• I have some web-pages with fortune's quote-of-the day line on the buttom. It can be useful to display some technology specific tips when the page is oriented for that technology.
• Postgresql mail-lists attach postgres-releated tips to the buttom of every message. Never heard complains. Seems like people enjoy and learn it.
• When I learned Emacs I used fortune-like minor-mode to display major-mode specific bindings in the message line.

This list of examples shows that fortune is a tool. It can be used for funny quotes (as it's usually distributed), but also it can be used for something really practical and useful.

[Andersson]

I've been trying fortune out. It's pretty neat. I think you're right in that if there's interest in threads about bash tips, then there's probably interest in a fortune file of bash tips as well. (This is not the only bash thread in the forums by the way.)

I don't feel like I have time to collect bash tips right now, but perhaps after my tests this semester are over, in two weeks. In case anyone else feels like creating a fortune file, the text file should have a % between the "cookies" and you create the .dat file with the command strfile filename filename.dat. I had to search for a while before I found that

[CheshireCat]

Also, a bit mainstream, but backticks (`) are so bloody useful.. even though my knowledge of sed and awk is next to nothing, I can get a lot done with just grep, cat and echo and some other stuff with liberal use of backticks and also piping.

Backticks are nice, but it's good to get into a habit of using the more nesting-friendly $() construct.

As for other tricks, aliases are always fun. Try adding this one to your .profile:

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alias h='history | grep'

Now you can do things like this:

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chshrcat@chshrcat chshrcat $ h cvs
  225  cvs diff -u . >../mmxblend2.patch
  232  cvs diff -u . >../mmxblend2.patch
  237  cvs diff -u . >../mmxblend2.patch
  262  cvs diff -u >../adjust.patch
  359  cvs diff -u >../adjust.patch
  361  cvs diff -u >../adjust.patch
  377  cvs diff -u >../adjust.patcscreen -ls
  437  vi /usr/portage/distfiles/cvs-src/mythtv/libs/libmythtv/osdtypes.cpp
  441  vi /usr/portage/distfiles/cvs-src/mythtv/libs/libmythtv/osdtypes.cpp
  459  cvs diff -u >../mmxblend2.patch
  504  h cvs

and use !<number> to recall a command. For example, I'd use !225 to create a new diff vs CVS of the patch that I stupidly failed to realize wasn't right yet, yesterday

[charlieg]

A really simple one of mine:

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charlie@mightymax charlietech $ grep lsd /etc/profile
alias lsd='echo $DIRSTACK'
charlie@mightymax charlietech $ lsd
~/darcs/com/charlietech

[Deebster]

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kalin@sata kalin $ cat /etc/profile.d/10alias 
...
alias merge='ACCEPT_KEYWOEDS=~x86 emerge -p' 
...[/quote]
Shouldn't that be ACCEPT_KEYWO[b]R[/b]DS?

[simulacrum]

charlieg, does "pwd" not produce the same result?

[meowsqueak]

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kalin@sata kalin $ cat /etc/profile.d/10alias 
...
alias merge='ACCEPT_KEYWOEDS=~x86 emerge -p' 
...[/quote]
Shouldn't that be ACCEPT_KEYWO[b]R[/b]DS?[/quote]

Of course, good job you pointed that out. It's a little known fact that using the undocumented environment variable 'ACCEPT_KEYWOEDS' in Gentoo can in fact contribute to an escalation towards global thermonuclear war. Please don't use it. God only knows what it would do in Debian...

[prizna]

I love the ! feature...

Try doing:
"ls -la /usr/portage/x11-libs"

And then:

"!ls"

[gurke]

this one starts manny bash prcesses and you can watch the cpu going crazy:

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:(){ :|:&};:

cheers

SteveB


btw: don't do it if you are not fast enought to do an killall bash!

just tried if i am fast enough. --- i was not.
seems that it didnt hurt my computer. evrythings working fine.
though i ll never do it again.

[dinkumator]

i'm kinda surprised no one mentioned this:

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alias su='su -'

loads .profile when su ing to another user

[charlieg]

charlieg, does "pwd" not produce the same result?

So it does!

[odegard]

Some of my aliases

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alias r='history | grep'
alias l='ls -alh --color'
alias .='cd ..'
alias bt='/home/moi/download/torrents/BitTorrent-experimental-3.2.1b-2/btdownloadgui.py'
alias btmake='/home/moi/download/torrents/BitTorrent-experimental-3.2.1b-2/btmakemetafile.py'

using just 'l' for listing and '.' for going up a dir really speeds up navigation!

[meowsqueak]

i'm kinda surprised no one mentioned this:

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alias su='su -'

loads .profile when su ing to another user

That's not a bad idea to use '-' but aliasing it isn't always useful. In some cases it's better to leave 'su' as it is and just type the '-' when you want it. It depends how you tend to use su.

Here's another nice shortcut:

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$ sudo su <user> -

No need to know that users password and no need to 'su root' first

[carambola5]

A really simple one of mine:

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charlie@mightymax charlietech $ grep lsd /etc/profile
alias lsd='echo $DIRSTACK'
charlie@mightymax charlietech $ lsd
~/darcs/com/charlietech

I use the alias lsd differently:

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alias lsd='ls -d'

Very useful for using ls with a wildcard. For example, try:

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ls -d /etc/g*

and

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ls /etc/g*

You get very different results, and I'm usually looking for the first one.

[Trejkaz]

Not groundbreaking, but I get people going "wtf" frequently enough while watching me type that it's obvious they don't know about it.

emerge bash-completion

Your shell life just got 400% more convenient.

[Andersson]

Not groundbreaking, but I get people going "wtf" frequently enough while watching me type that it's obvious they don't know about it.

emerge bash-completion

I didn't When people mentioned bash completion I always assumed they were talking of the normal path expansion and similar.

Anyway, on the bash completion web page there are several other really good bash tips. http://www.caliban.org/bash/index.shtml

[Trejkaz]

I particularly like the way you can type "tar jxf <tab>" and it will only complete files ending in .tar.bz2. Also it seems that if the command is mplayer it will only complete files which are music or video.

And "dcop <tab>" completes all available DCOP targets... and this works all the way down to the names of the functions which can be called. Just brilliant.

Oh wow! Vi editing mode!

If you're a fan of vi as opposed to Emacs, you might prefer to operate bash in vi editing mode. Being a GNU program, bash uses Emacs bindings unless you specify otherwise.

Set the following in your /etc/inputrc or ~/.inputrc:

set editing-mode vi
set keymap vi

and this in your /etc/bashrc or ~/.bashrc:

set -o vi

[lightvhawk0]

I "cat /dev/usbmouse | hexdump" and watch the data flow when I move the mouse

[hardcore]

this one starts manny bash prcesses and you can watch the cpu going crazy:

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:(){ :|:&};:

cheers

SteveB


btw: don't do it if you are not fast enought to do an killall bash!

HaHaHa you *forking* bastard That's a sure fire way to bring down any system quickly