PS in Unix

By Jwalitha N J, Divya Monisha

Syntax : ps [options]

Ps is used to list all the active process. It list the process ID, parent processs ID, user ID, name, terminal.

There are various options that could be given along the ps command such as

To list simple process

Ps –A or ps-e,

Ps –a

Ps T

Ps r

Ps f

To list standard process

Ps –ef

Ps –eF

Ps –ely

To list BSD format

Ps –aux

Ps aux

To list root process ps –u root

To list threads ps -eLF

Syntax: ps [options]

Definition: ps lists the information of active process.

There are various options that could be given in ps , they are as follows

1. ps

When ps alone is executed at the Linux terminal the output generated is

PID TTY TIME CMD

5839 pts/2 00:00:00 bash

5885 pts/2 00:00:00 ps

Here bash is the name of the working terminal and the process that currently running is man ps. Hence here the list has two processes with process-id(PID),file name of the terminal(tty),TIME and CMD

2. ps –A or ps –e

Selects all the process. The output contains PID,TTY,TIME and CMD

3. ps – a

Selects all the process except the process associated with the terminal.

PID TTY TIME CMD

5849 pts/0 00:00:00 man

5858 pts/0 00:00:00 less

5897 pts/2 00:00:00 ps

4. ps –d

Select all process except session leaders. Session leader is one that creates another session.

5. ps r

Selects only running process.

PID TTY STAT TIME COMMAND

5685 pts/0 R+ 0:00 ps r

6. ps T

Selects those process that are associated with the terminal

PID TTY STAT TIME COMMAND

5637 pts/0 Ss 0:00 bash

5702 pts/0 R+ 0:00 ps t

Here bash is the name the working terminal and the process that is associated with bash is ps t command that is currently running.

There are options that displays files in particularformat such as standard format and BSD format

To display standard format process

1. ps -e : selection of all process.

2. Ps –ef

UID PID PPID C STIME TTY TIME CMD

root 1 0 0 19:56 ? 00:00:00 /sbin/init

root 2 0 0 19:56 ? 00:00:00 [kthreadd]

root 3 2 0 19:56 ? 00:00:00 [ksoftirqd/0]

root 4 2 0 19:56 ? 00:00:00 [kworker/0:0]

3. ps -eF

UID PID PPID C STIME TTY TIME CMD

root 1 0 0 19:56 ? 00:00:00 /sbin/init

root 2 0 0 19:56 ? 00:00:00 [kthreadd]

root 3 2 0 19:56 ? 00:00:00 [ksoftirqd/0]

root 4 2 0 19:56 ? 00:00:00 [kworker/0:0]

4. ps -ely

S UID PID PPID C PRI NI RSS SZ WCHAN TTY TIME CMD

S 0 1 0 0 80 0 1812 730 poll_s ? 00:00:00 init

S 0 2 0 0 80 0 0 0 kthrea ? 00:00:00 kthreadd

S 0 3 2 0 80 0 0 0 run_ks ? 00:00:00 ksoftirqd/0

S 0 4 2 0 80 0 0 0 worker ? 00:00:00 kworker/0:0

To display process of BSD format

1. ps -aux

This selects process those associated with a particular user.

PID TTY STAT TIME COMMAND

1 ? Ss 0:00 /sbin/init

2 ? S 0:00 [kthreadd]

3 ? S 0:00 [ksoftirqd/0]

2. ps aux

This selects all the process with the complete details The difference in aux and -aux is that , in -aux the user name is given example –ausylar.If that user does not exists then the command is treated as aux displaying all the process.

To get information on threads we use the options as

1. ps -eLf

Example:

UID PID PPID LWP C NLWPSZ RSS PSR STIME TTY TIME CMD

root 1 0 1 0 1 549 704 0 19:51 ? 00:00:01 init [5]

root 2 0 2 0 1 0 0 1 19:51 ? 00:00:00 [kthreadd]

sylar 5795 5637 5795 0 1 650 852 0 20:11 pts/0 00:00:00 ps -eLF

Sample program

ps // to list current working process.

#ps –e

ps u // to list process that run as root

ps -u root

ps -eopid // to list all process PID.

ps -p 2454 // to list the name of the process with PID 2454.

Output

// output for ps

PID TTY TIME CMD

5927 pts/3 00:00:00 bash

6006 pts/3 00:00:00 sh

6007 pts/3 00:00:00 ps

// output for ps u

USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND

sylar 5637 0.0 0.0 5028 2272 pts/0 Ss 19:53 0:00 bash

sylar 5652 0.0 0.0 5028 2268 pts/2 Ss 19:53 0:00 bash

sylar 5668 0.0 0.0 4508 1656 pts/2 S+ 19:53 0:00 man ps

sylar 5677 0.0 0.0 3848 996 pts/2 S+ 19:53 0:00 less

sylar 5854 0.0 0.0 2600 868 pts/0 R+ 20:18 0:00 ps u

// output for ps –u root

PID TTY TIME CMD

1 ? 00:00:01 init

2 ? 00:00:00 kthreadd

3 ? 00:00:00 ksoftirqd/0

4 ? 00:00:01 kworker/0:0

6 ? 00:00:00 migration/0

7 ? 00:00:00 watchdog/0

8 ? 00:00:00 migration/1

10 ? 00:00:00 ksoftirqd/1

12 ? 00:00:00 watchdog/1

13 ? 00:00:00 migration/2

// output for ps -eopid

PID

1

2

3

4

6

7

.. 6008

//output for ps –p 2454

PID TTY TIME CMD

2454 tty5 00:00:00 mingetty