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===The following is networking specific=== | ===The following is networking specific=== | ||
Revision as of 09:41, 28 June 2010
This page requires major clean-up!
The basics
Writing a shell function
user@computer:~$ minute() { foo=`date +%S`; echo $foo; if [ "$foo" -lt "30" ]; then echo "under half"; else echo "over half"; fi; }
- Simple shell function that uses a variable and if/then/else logic
user@computer:~$ minute
29
under half
- Using the shell function we just wrote, outputs the current time in seconds (only the seconds part) and whether it is closer to the last minute or next minute. Shell functions are only available for the terminal session. Save in .bashrc or .profile to be persistent/saved
user@computer:~$ minute
31
over half
Intermediate
user@computer:~$ /usr/bin/camera &
- Everything is run from a terminal, quite literally in *NIX. A GUI program is a running instance of a terminal process. Therefore the camera program can be launched. The & amperstand tells it to disassociate from the current terminal and create it's own process
user@computer:~$ ln -s /sbin/ifconfig /usr/bin
- The user PATH does not include /sbin for some reason by default on NITs, which is annoying as typing in /sbin/ifconfig - which should be in /usr/bin/ anyway. Thus we are going to symlink it.
user@computer:~$ ifconfig | grep "inet addr"
- Example use of grep. grep outputs the entire line matching the pattern, in this case "inet addr" which is piped into it from the output of ifconfig using the | pipe character
user@computer:~$ ifconfig | grep "inet addr" | awk '{ print $2 }' | cut -d : -f2
- Advanced example pipes from ifconfig to grep to awk and finally to cut to output the clean IP address which can then be fed into something else if desired
Logged in as root from here on out. Not necessary for every command but for some of them. If you have sudoer installed you can simply prefix each command with sudo. If not you are gonna use an equivalent of sudo su - or simply login a root using another method. For easyroot users, simply type $ root and enter.
This next section is Debian-based specific
The following is networking specific
root@computer:~# ssh name@192.168.1.100
...
Are you sure you want to continue connecting (yes/no)?yes
name@desktop:~$ exit
- SSH example. Specify the user _at_ the IP address of the computer you want to access. Keep in mind that this works only over LAN by default (you need to forward port 22 on the router and give outside IP address or use some type of fake VPN). If you get a RSA error message, simply delete ~/.ssh/known_hosts using $ rm ~/.ssh/known_hosts Type exit to leave remote session
root@computer:~# scp name@192.168.1.100:/home/name/randomfile /home/user/
user@computer:~$ ls /home/user/randomfile
- File is copied from remote computer to local computer to user's home directory. Root's home directory is /root
root@computer:~# ssh name@192.168.1.100
name@desktop:~$ screen
name@desktop:~$ hello
- Leaves a shared session open
friend@laptop:~$ ssh name@192.168.1.100
name@desktop:~$ hello world
- Allows you to work with a friend or simply resume a session later. Good for long tasks that need to disconnect from a machine and reconnect later.
root@computer:~# ssh name@192.168.1.100
name@desktop:~$ screen -ln nano /etc/resolv.conf
- [Nano instance]
[CTRL]+[A]+[D]
- Detaches from a screen leaving a process running on a remote machine
name@desktop:~$ exit
root@computer:~# ssh name@192.168.1.100
name@desktop:~$ screen -r
- [Nano instance]
[CTRL]+[X]
name@desktop:~$ exit
- [screen is terminating]
name@desktop:~$ exit
root@computer:~#
- Detach a process. If you are running a process via ssh on a remote machine, the process is killed when the connection is interrupted, unless it was detached with screen.