Terminal (Bash) - Process Management and Conditional execution

Process Management

Run command in background

Imagine that you want to execute a command, but you want to keep using the prompt. To do that you need to execute the command like this:

$ command1 &
[1] 1234

$ 

The command1 will run in the background and the process id (PID) is 1234.

List processes

To list the processes running at your machine we can use the "ps" command.

$ ps
  PID TTY          TIME CMD
    8 tty1     00:00:00 bash
 1383 tty1     00:00:00 ps

Kill processes

To kill a process currently running we can use the "kill" command

$ kill 1234
[2]+ Terminated command1

The "kill" command sends signals to processes. And there is a variety of signals that the the "kill" command can send to processes.

Signal Number	Name	Description
1	SIGHUP	Hang up signal
2	SIGINT	Interrupt signal
9	SIGKILL	Kill signal
15	SIGTERM	Termination signal

Conditional Execution

Run command1 and if succeeds, then, run command2

command1 && command2

Run command2 if, and only if, command1 fails

command1 || command2