hemanth/unix-tricks.md

## unix-tricks.md

      
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              unix-tricks.md
            
          
    I have marked with a * those which I think are absolutely essential
Items for each section are sorted by oldest to newest. Come back soon for more!
BASH

In bash, 'ctrl-r' searches your command history as you type


Add "set -o vi" in your ~/.bashrc to make use the vi keybindings instead
of the Emacs ones. Takes some time to get used to, but it's fantastic!
Input from the commandline as if it were a file by replacing
'command < file.in' with 'command <<< "some input text"'
'^' is a sed-like operator to replace chars from last command
'ls docs; ^docs^web^' is equal to 'ls web'. The second argument can be empty.


'!!:n' selects the nth argument of the last command, and '!$' the last arg
'ls file1 file2 file3; cat !!:1-2' shows all files and cats only 1 and 2


More in-line substitutions: http://tiny.cc/ecv0cw
'nohup ./long_script &' to leave stuff in background even if you logout
'cd -' change to the previous directory you were working on
'ctrl-x ctrl-e' opens an editor to work with long or complex command lines


Use traps for cleaning up bash scripts on exit http://tiny.cc/traps
'shopt -s cdspell' automatically fixes your 'cd folder' spelling mistakes

PSEUDO ALIASES FOR COMMONLY USED LONG COMMANDS

function lt() { ls -ltrsa "$@" | tail; }
function psgrep() { ps axuf | grep -v grep | grep "$@" -i --color=auto; }
function fname() { find . -iname "$@"; }

VIM

':set spell' activates vim spellchecker. Use ']s' and '[s' to move between
mistakes, 'zg' adds to the dictionary, 'z=' suggests correctly spelled words
check my .vimrc http://tiny.cc/qxzktw and here http://tiny.cc/kzzktw for more

TOOLS

'htop' instead of 'top'


'ranger' is a nice console file manager for vi fans
Use 'apt-file' to see which package provides that file you're missing
'dict' is a commandline dictionary
Learn to use 'find' and 'locate' to look for files
'find . -type d -exec chmod g+x {} ;' let people in your group access
folders without messing up file permissions (never do 'chmod g+x * -R'!)
Compile your own version of 'screen' from the git sources. Most versions
have a slow scrolling on a vertical split or even no vertical split at all


'trash-cli' sends files to the trash instead of deleting them forever.
Be very careful with 'rm' or maybe make a wrapper to avoid deleting '' by
accident (e.g. you want to type 'rm tmp' but type 'rm tmp *')


'file' gives information about a file, as image dimensions or text encoding
'awk '!x[$0]++'' to check for duplicate lines
'echo start_backup.sh | at midnight' starts a command at the specified time
Pipe any command over 'column -t' to nicely align the columns


Google 'magic sysrq' and learn how to bring you machine back from the dead


'diff --side-by-side fileA.txt fileB.txt | pager' to see a nice diff


'j.py' http://tiny.cc/62qjow remembers your most used folders and is an
incredible substitute to browse directories by name instead of 'cd'


'dropbox_uploader.sh' http://tiny.cc/o2qjow is a fantastic solution to
upload by commandline via Dropbox's API if you can't use the official client
learn to use 'pushd' to save time navigating folders (j.py is better though)
if you liked the 'psgrep' alias, check 'pgrep' as it is far more powerful

NETWORKING

SMB is better than NFS for most cases. 'sshfs_mount' is not really stable,
any network failure will be troublesome
'python -m SimpleHTTPServer 8080' shares all the files in the current
folder over HTTP, port 8080
'ssh -R 12345:localhost:22 server.com "sleep 1000; exit"' forwards
server.com's port 12345 to your local ssh port, even if you machine
is not externally visible on the net.
Now you can 'ssh localhost -p 12345' from server.com and you will
log into your machine.
'sleep' avoids getting kicked out from server.com for inactivity


Read on 'ssh-keygen' to avoid typing passwords every time you ssh


'socat TCP4-LISTEN:1234,fork TCP4:192.168.1.1:22' forwards your port
1234 to another machine's port 22. Very useful for quick NAT redirection.


Configure postfix to use your personal Gmail account as SMTP:
http://tiny.cc/n5k0cw. Now you can send emails from the command line.
'echo "Hello, User!" | mail user@domain.com'


Some tools to monitor network connections and bandwith:
'lsof -i' monitors network connections in real time
'iftop' shows bandwith usage per connection
'nethogs' shows the bandwith usage per process


Use this trick on .ssh/config to directly access 'host2' which is on a private
network, and must be accessed by ssh-ing into 'host1' first
Host host2
ProxyCommand ssh -T host1 'nc %h %p'
HostName host2


Pipe a compressed file over ssh to avoid creating large temporary .tgz files
'tar cz folder/ | ssh server "tar xz"'
                               -~-


(CC) by-nc, Carles Fenollosa carles.fenollosa@bsc.es
Retrieved from http://mmb.pcb.ub.es/~carlesfe/unix/tricks.txt
Last modified: jue 07 mar 2013 04:21:12  CET