maemo.org - Talk - Where to learn x terminal?

I think that last post might seem snobby so here's a quick primer to make up for that.

Open your favorite terminal emulator (osso-xterm) or a Virtual Terminal (desktop/laptop). On a desktop my preference is gnome-terminal.

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user@computer:~$ echo "hello world"
hello world
says/outputs/prints text to sdtout
user@computer:~$ echo $USER
user
says/outputs/prints the currently logged in user's name
user@computer:~$ echo $PWD
/home/user
says/outputs/prints the current CD'ed directory
user@computer:~$ cd /home/user/MyDocs
Change Directory to another one. Can also be relative location, in this case $ cd MyDocs
user@computer:~/MyDocs$ echo $PWD
/home/user/MyDocs
user@computer:~/MyDocs$ cd ~
Change Directory to home directory. Can also be relative location, in this case $ cd ..
user@computer:~$ mkdir asdf
Create a directory/folder
user@computer:~$ rm -R /home/user/asdf
Be very careful with the remove command. Especially with the -R recursive parameter which deletes any files and folders within a specified folder
user@computer:~$ uname -r
2.6.21-omap1
List the kernel version. the -a parameter outputs all known information
user@computer:~$ ls -A /home/user/MyDocs
.documents .......... .sounds
.games .................. .videos
.images ................. randomfile
Lists all files and directories, including hidden ones. Hidden files and directories start with a dot/period
user@computer:~$ cat /etc/resolv.conf
#nameserver 127.0.0.1
nameserver 192.168.1.1
#nameserver 4.2.2.2
Cat spits out an entire text file to terminal. resolv.conf (remember *NIX is case-sensitive) is where DNS servers are stored. The # pound character comments/"comments out" aka disables a line of text in a BASH script/file
user@computer:~$ ps | awk '{ print $5 }'
...
/usr/bin/osso-xterm
/usr/libexec/gnome-vfs-daemon
bash
ps
awk
ps lists running processes, you might also be interested in the interactive top command. piped to awk which in this case says to only show the 5th column (separated by tab characters)
user@computer:~$ foobar='example'; echo $foobar
example
Basic example of a variable
user@computer:~$ uname -s > /dev/shm/os; cat /dev/shm/os
Example of directing output to a file. Files stored in /dev/shm are stored directly in RAM and thus are deleted on shutdown
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
user@computer:~$ /usr/bin/camera &
Everything is run from a terminal, quite literally in *NIX. A GUI program is simply a GUI over 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
root@computer:~# apt-cache search nano
nano-tiny - free Pico clone
traceroute-nanog - Determine route of packets
nano - nano editor
Searches repos for packages by keyword
root@computer:~# apt-get install nano
install package nano. It's an easy to use CLI text editor.
root@computer:~# wget http://nitstuff.appspot.com/dists/ch....0.6_armel.deb
Instead of using the repos using wget to download .deb package from website.
root@computer:~# dpkg -i nano_2.0.6_armel.deb
Installing locally saved debian package.

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.