skill Command in Linux
The skill command in Linux is a powerful and flexible program that allows users to send signals to processes. These signals can be used to direct, regulate, or terminate processes in a systematic way. Unlike the more frequent kill command, skill provides an easier and more user-friendly syntax by letting users select processes based on usernames, terminal names, or other identifiers.
The main purpose of skill is to send signals to processes based on attributes like username, process ID (PID), terminal, or command name. It is part of the procps package and works as a more intuitive alternative to the kill command, especially for users looking for targeted process management.
Table of Contents
Here is a comprehensive guide to the options available with the skill command −
Syntax of skill Command
The basic syntax for the skill command is as follows −
skill [OPTIONS] SIGNAL [PATTERN]
In this syntax,
- OPTIONS − Indicates additional characteristics to identify or filter the target processes.
- SIGNAL − Indicates the type of signal (such as TERM, KILL, or STOP) that should be sent to the processes.
The process identifier, such as the PID, username, terminal name, or process name, is represented by the pattern.
skill Command Options
The skill command provides numerous parameters to make process control more flexible and targeted. Here are some of the widely used options −
| Option | Description |
|---|---|
| -f, --fast | Enables fast mode (currently not implemented). |
| -l, --list | Lists all available signal names that can be sent to processes. |
| -L, --table | Provides a neatly ordered table of all signal names for enhanced readability. |
| -n, --no-action | Simulates the command by illustrating what would happen without actually sending any signals. |
| -v, --verbose | Provides extensive information about what the command is doing. |
| -w, --warnings | Enables warning messages (currently not implemented). |
| -c, --command <command> | Targets processes by their command name. |
| -p, --pid <pid> | Focuses on a particular process ID (PID). |
| -t, --tty <tty> | Targets the processes that are active on a particular terminal. |
| -u, --user <username> | Targets every process that a particular user owns. |
| --ns <pid> | Targets every process that shares a namespace with the designated PID. |
| --nslist <ns,...> | Lists the namespaces that the --ns option will take into account. |
Examples of skill Command in Linux
Letâs investigate a few practical instances of the skill command on Linux environment −
- Listing Available Signals
- Displaying Signals in a Table
- Simulating Process Termination
- Interactive Mode for Managing Process
- Killing Processes by Command Name
- Targeting a Specific Process by PID
- Managing Processes Based on Terminal
- Managing Processes by Username
Listing Available Signals
To display all the signals that can be transmitted to processes, use the -l option −
skill -l
This will output all signal names, such as HUP, KILL, STOP, and their respective descriptions.
Displaying Signals in a Table
For a more organized view of signal names, you can use the -L option −
skill -L
This command formats the signal names into a neat table, making it easier to understand their functions and numeric representations.
Simulating Process Termination
If you want to check which processes would be affected by a command without actually terminating them, use the -n option −
skill -n -KILL firefox
This command shows all Firefox processes that would be terminated if the KILL signal were executed but does not actually kill them.
Interactive Mode for Managing Processes
To interactively manage processes, allowing confirmation before taking actions, use the -i option −
skill -i STOP
Youâll be prompted to confirm each action before suspending the targeted processes.
Killing Processes by Command Name
To terminate all instances of a specific command, such as nginx, you can use −
skill -c nginx KILL
This command sends the KILL signal to all processes named nginx.
Targeting a Specific Process by PID
If you know the Process ID (PID) of a process and need to terminate it, use −
skill -p 5678 TERM
This sends the TERM signal to process ID 5678, allowing it to terminate gracefully.
Managing Processes Based on Terminal
If you want to target all processes associated with a specific terminal (e.g., tty3), you can use −
skill -t tty3 KILL
This command terminates all processes running on terminal tty3 â
Managing Processes by Username
To terminate all processes owned by a specific user (e.g., john), use −
skill -u john KILL
It kills all processes initiated by the user john â
Conclusion
The skill command in Linux is a comprehensive and user-friendly tool for process management. Its extensive parameters allow users to target processes based on attributes like command names, PIDs, terminals, or usernames, enabling better precision than the usual kill command.
With capabilities such as signal listing, simulation mode, and namespace matching, the skill command empowers system administrators to control operations efficiently and effectively.
By knowing the skill command, users may expedite workflows, boost control over their systems, and achieve optimal performance in Linux environments.