Handy commands in Mac/Linux systems

Here’s a list of common commands I use in Linux. I will continue to update this list with more stuff.

1. Checking fireball logs:

[code lang=”bash” gutter=”false”]
cat /var/log/appfirewall.log

# You will see stuff like
Jun 21 10:37:51 prakhars-MacBook-Pro Firewall[90]: postgres is listening from 0.0.0.0:5432 proto=6
Jun 21 10:38:11 prakhars-MacBook-Pro Firewall[90]: mysqld is listening from ::ffff:0.0.0.0:3306 proto=6
Jun 21 10:40:21 prakhars-MacBook-Pro Firewall[90]: Dropbox is listening from 0.0.0.0:17500 proto=6
Jun 21 10:40:21 prakhars-MacBook-Pro Firewall[90]: java is listening from ::ffff:0.0.0.0:0 proto=6
Jun 21 10:44:38 prakhars-MacBook-Pro Firewall[90]: GoogleTalkPlugin is listening from 127.0.0.1:49198 proto=6
Jun 21 10:45:35 prakhars-MacBook-Pro Firewall[90]: python is listening from 127.0.0.1:8000 proto=6
[/code]

2. screen command: Use it to create parallel sessions in terminal. Useful for running long processes on remote servers even after signing out of server.Usage:
   [code lang=”bash”]
   screen
   # This creates a separate screen.

   screen -ls
   #lists all attached/detached screens IDs

   screen -x 13152
   # Enter (Attach) screen ID 13152 (just an example, can be any ID number)

   echo $STY
   # Displays current screen ID you are working in.
   [/code]
   Ctrl-a d Detach from current screen.

3. dpkg --get-selections List all installed packages. (Only on debian systems like Ubuntu which support apt-get)
   Smartly grep to find package you are looking for eg- dpkg --get-selections | grep mysql