Favorite Unix Commands

python -m SimpleHTTPServer
Serve current directory tree at http://$HOSTNAME:8000/

cd -
change to the previous working directory

mtr google.com
mtr, better than traceroute and ping combined
mtr combines the functionality of the traceroute and ping programs in a single network diagnostic tool.
As mtr starts, it investigates the network connection between the host mtr runs on and HOSTNAME. by sending packets with purposly low TTLs. It continues to send packets with low TTL, noting the response time of the intervening routers. This allows mtr to print the response percentage and response times of the internet route to HOSTNAME. A sudden increase in packetloss or response time is often an indication of a bad (or simply over?loaded) link.

> file.txt
Empty a file

$ssh-copy-id user@host
Copy ssh keys to user@host to enable password-less ssh logins.

reset
Salvage a borked terminal
If you bork your terminal by sending binary data to STDOUT or similar, you can get your terminal back using this command rather than killing and restarting the session. Note that you often won't be able to see the characters as you type them.

ffmpeg -f x11grab -s wxga -r 25 -i :0.0 -sameq /tmp/out.mpg
Capture video of a linux desktop

'ALT+.' or '<ESC> .'
Place the argument of the most recent command on the shell
When typing out long arguments, such as:
cp file.txt /var/www/wp-content/uploads/2009/03/
You can put that argument on your command line by holding down the ALT key and pressing the period '.' or by pressing <ESC> then the period '.'. For example:
cd 'ALT+.'
would put '/var/www/wp-content/uploads/2009/03/ as my argument. Keeping pressing 'ALT+.' to cycle through arguments of your commands starting from most recent to oldest. This can save a ton of typing.

mount | column -t
currently mounted filesystems in nice layout
Particularly useful if you're mounting different drives, using the following command will allow you to see all the filesystems currently mounted on your computer and their respective specs with the added benefit of nice formatting.

ssh -N -L2001:localhost:80 somemachine
start a tunnel from some machine's port 80 to your local post 2001
now you can access the website by going to http://localhost:2001/

echo "ls -l" | at midnight
Execute a command at a given time
This is an alternative to cron which allows a one-off task to be scheduled for a certain time.
dig +short txt <keyword>.wp.dg.cx
Functions: dig
Query Wikipedia via console over DNS
Query Wikipedia by issuing a DNS query for a TXT record. The TXT record will also include a short URL to the complete corresponding Wikipedia entry.You can also write a little shell script like:
$ cat wikisole.sh
#!/bin/sh
dig +short txt ${1}.wp.dg.cx
and run it like
./wikisole.sh unix
were your first option ($1) will be used as search term.

netstat -tlnp
Lists all listening ports together with the PID of the associated process
The PID will only be printed if you're holding a root equivalent ID.
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dd if=/dev/dsp | ssh -c arcfour -C username@host dd of=/dev/dsp
output your microphone to a remote computer's speaker
This will output the sound from your microphone port to the ssh target computer's speaker port. The sound quality is very bad, so you will hear a lot of hissing.

curl -u user:pass -d status="Tweeting from the shell" http://twitter.com/statuses/update.xml
Update twitter via curl

!!:gs/foo/bar
Runs previous command replacing foo by bar every time that foo appears
Very useful for rerunning a long command changing some arguments globally.
As opposed to ^foo^bar, which only replaces the first occurrence of foo, this one changes every occurrence.

mount -t tmpfs tmpfs /mnt -o size=1024m
Mount a temporary ram partition
Makes a partition in ram which is useful if you need a temporary working space as read/write access is fast.
Be aware that anything saved in this partition will be gone after your computer is turned off.

man ascii
Quick access to the ascii table.

sshfs name@server:/path/to/folder /path/to/mount/point
Mount folder/filesystem through SSH
Install SSHFS from http://fuse.sourceforge.net/sshfs.html
Will allow you to mount a folder security over a network.

curl ifconfig.me
Get your external IP address
curl ifconfig.me/ip -> IP Adress
curl ifconfig.me/host -> Remote Host
curl ifconfig.me/ua ->User Agent
curl ifconfig.me/port -> Port
thonks to http://ifconfig.me/



use iperf. It's a client server arrangement in that you run it in server mode at one end and connect to its from another computer on the other side of the network.

One both machines run:

sudo apt-get install iperf
Then on Computer A:

iperf -s
And on Computer B:

iperf -c <address of Computer A>
On the client machine, you'll see something like this:

oli@bert:~$ iperf -c tim
------------------------------------------------------------
Client connecting to tim, TCP port 5001
TCP window size: 16.0 KByte (default)
------------------------------------------------------------
[  3] local 192.168.0.4 port 37248 connected with 192.168.0.5 port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec  1.04 GBytes    893 Mbits/sec
Of course, if you're running a firewall on the server machine, you'll need to allow connections on port 5001 or change the port with the -p flag.


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

SHELL - APPEND ONE FILE TO ANOTHER IN LINUX - STACK OVERFLOW
cat file2 >> file1


Using `find` is nice to get just directories:
$ find . -type d -maxdepth 1


Here's my list, a very compact plaintext file: http://mmb.pcb.ub.es/~carlesfe/unix/tricks.txt

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
  '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

VIM
- ':set spell' activates vim spellchecker. Use ']s' and '[s' to move between
  mistakes, 'zg' adds to the dictionary, 'z=' suggests correctly spelled words

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
- 'sort | uniq' 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

NETWORKING
- SMB is better than NFS. Use 'sshfs_mount' as a last resort,
  any network failure will be trouble
- '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 [email protected]'
- 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

                                     -~-

(CC) by-nc, Carles Fenollosa <[email protected]>
Retrieved from http://mmb.pcb.ub.es/~carlesfe/unix/tricks.txt
Last modified: Mon 07 Jan 2013 09:48:46 PM CET