Bash ps - Report a Snapshot of Current Processes

All examples below use a hypothetical process list for demonstration:

PID TTY          TIME CMD
1234 pts/0    00:00:01 bash
5678 pts/1    00:00:02 python
9101 pts/2    00:00:03 node

Understanding the Output

The ps command output consists of several columns, each representing different aspects of the system's processes:

• PID: Process ID, a unique identifier for each process.
• TTY: Terminal type associated with the process.
• TIME: Total CPU time used by the process.
• CMD: The command that started the process.

Basic Usage

To display a snapshot of current processes, use ps:

ps
PID TTY          TIME CMD
1234 pts/0    00:00:01 bash
5678 pts/1    00:00:02 python
9101 pts/2    00:00:03 node

Options

The ps command has options to change how it works:

• -e - Show all processes
• -f - Show detailed information
• -u - Show processes for a specific user
• -a - Show all processes with a terminal
• -x - Show processes without a terminal

Show All Processes

The -e option allows you to show all processes.

ps -e
PID TTY          TIME CMD
1234 pts/0    00:00:01 bash
5678 pts/1    00:00:02 python
9101 pts/2    00:00:03 node

Show Detailed Information

The -f option allows you to show detailed information.

ps -f
UID        PID  PPID  C STIME TTY          TIME CMD
user      1234     1  0 08:00 pts/0    00:00:01 bash
user      5678  1234  0 08:01 pts/1    00:00:02 python
user      9101  5678  0 08:02 pts/2    00:00:03 node

Show Processes for a Specific User

The -u option allows you to show processes for a specific user.

ps -u user
PID TTY          TIME CMD
1234 pts/0    00:00:01 bash
5678 pts/1    00:00:02 python

Show Processes with a Terminal

The -a option allows you to show all processes with a terminal.

ps -a
PID TTY          TIME CMD
1234 pts/0    00:00:01 bash
5678 pts/1    00:00:02 python

Show Processes without a Terminal

The -x option allows you to show processes without a terminal.

ps -x
PID TTY          TIME CMD
9101 ?        00:00:03 node

Combining Options

Options can be combined to provide more detailed output. For example, ps -ef shows all processes with detailed information.

ps -ef
UID        PID  PPID  C STIME TTY          TIME CMD
user      1234     1  0 08:00 pts/0    00:00:01 bash
user      5678  1234  0 08:01 pts/1    00:00:02 python
user      9101  5678  0 08:02 pts/2    00:00:03 node