A process is an instance of a running program. A process can spawn child processes. The ps command shows running processes and options like -e and -f provide more details. An interactive process launched by the shell that is not a daemon is called a job. Child processes are not jobs. Daemons run in the background. The jobs command shows running jobs. Processes can run in the background using & or by suspending and backgrounding with CTRL-Z and bg. The fg command brings suspended/background jobs to the foreground by job number or most recent. The kill command terminates processes and jobs by process ID, job number, or process name.

1. Processes

2. • A process is created every time you issue a command. It is
an instance of a running program.
• Question: What is an instance? (Think programming)
• A running process may spawn child processes
• e.g., a man process may invoke your default pager, thereby spawning a more process.
• The command ps will let you see all of your running processes. Some useful
options include:
• -e – lets you see information about all running processes, even those that are not yours.
• -f – displays more detailed information
Processes

3. • A interactive process launched by the shell that is not a daemon is called a
job.
• Child processes would not be jobs
• Question: What is a daemon?
• To see your running jobs, issue the jobs command.
Jobs

4. • There are two was to run processes/jobs in the background:
1. Start the job as you normally would. Suspend the job. Tell the system to
run the suspended job in the background; e.g.,
• man sort
• CTRL^Z
• Bg
2. Start the job in the background using the
ampersand:
• man sort &
• Question: Which of these is a command line command and why?
Running processes/jobs in the background

5. • To foreground your most recently suspended or backgrounded job, type fg
• To foreground another job:
• Determine its job number, via the jobs command
• Suppose you were interested in foregrounding job number 3. You would then issue the
command:
fg %3
Foregrounding a job

6. • To kill a process:
kill –SIGKILL processID or kill –s 9 processID
• To kill a job:
 kill –SIGKILL %job-number
**Note the percent symbol!**
• To kill all processes by name rather than process ID:
kill –SIGKILL name
For example: kill –SIGKILL man will all instances of the man command as well as any
child processes
Killing jobs and processes