Takuma Yoneda

How Linux Works -- Command Line Operations --

Listing and Manipulating Processes

About ps options

Confusingly, you can specify options in three different ways -- Unix, BSD, and GNU.
Most people use BSD style.

  • ps x Show all of your running processes.
  • ps ax Show all processes on the system, not just the ones you own.
  • ps u Include more detailed information on processes.
  • ps w Show full command names, not just what fits on one line.

Note that you can combine options like ps aux.

Killing Processes

To terminate a process, send it a signal with the kill command. A signal is a
message to a process from the kernel.
There are plenty of signals.
The default signal is TERM (terminate).
Instead of killing the process, you can freeze it with:
$ kill -STOP pid
and continue with:
$ kill -CONT pid

The most brutal way to terminate a process is with the KILL signal.
Other signals give the process a chance to clean up after itself, but KILL
does not.

Using ctrl-C to terminate a process that is running in the current terminal is the
same as using kill to end the process with the INT (interrupt) signal.

File Operations

A symbolic link is a file that points to another file or directory.

$ ln -s target linkname

  • -s specifies a symbolic link

Without -s, ln creates a hard link, which points directly to the file date instead of another filename as asymbolic link does.
This can be quite confusing if you do not have enough knowledge.



To create an archive, you can use tar

$ tar cvf archive.tar file1 file2 ...

  • c denotes create mode
  • v denotes verbose mode
  • f denotes file option ( the following argument must be the archive file for tar to create)


$ tar xvf archive.tar

  • x denotes extract mode
    By using t flag instead of x, you can verify the archive`s basic integrity and print the names of all files inside.
    Adding p option preserve original permissions instead of automatically applying umask to extracted files.

Contents above are entirely based on How Linux Works, 2nd Edition: What Every Superuser Should Know