Unix Command Line Resources


Unix Command Line help

commands
Display the manual for command (man <command>)
Navigation (cd <path>)
Display directory Contents (ls -lh <path>)
Show current directory path (pwd)
Clear the terminal screen (clear)
Quit the command line session (exit)
Create a virtual terminal (screen -S <name>)
Check what processes are running (ps fwux)
Terminate a process (kill -HUP <pid>  or   kill -9 <pid>)
List top running processes (top)
Make a command share system resources fairly (nice <command>)
Make an existing process share system resources fairly (renice +<0 to 20> <pid>)
Display file contents (cat <file>)
Display file contents one page at a time (less <file>)
Search for text strings in a file (grep -i <pattern> <file>)

Display the manual for a command
command: man  <command>
description:
 * shows the manual page for <command>. This is a great way to learn of the other options and features a command has and also related commands
 * adding '-k' searches through all manuals for occurances of the text you enter as <command>

Navigation
command: cd  <path>
description:
 * change directory to <path>
 * used without <path> will change to your home directory

Display directory contents
command: ls -lh <path>
description:
 * shows the contents of directory at <path>
 * 'l' shows extra details such as permissions, file size and date
 * 'h' shows the file size in human readable form (in GB, MB, etc)
 * used without <path> will show the curent directory

Show current directory path
command: pwd
description:
 * prints out the path of the current directory you are in

Clear the terminal screen
command: clear
description:
  * clears the text from the termal (pressing ctrl-L does the same)

Quit the command line session
command: exit
description:
  * quits the shell session, which may close the terminal window or will disconnect from the remote server if you connected via SSH

Create a virtual terminal
command: screen -S <name>
description:
 * creates a virtual terminal session that you can reconnect to later
 * (text based) programs can continue to run in the virtual terminal even if you disconnect from the server
 * <name> is a unique name to help you identify and reconnect to your screen (you can create multiple screens)
 * use screen -rd <name> to reconnect to your screen session ('r' is reattach and 'd' is detach if still connected elsewhere)
 * colour text sometimes does not show up, one workaround is to let screen start the program, such as: screen -S filemanager mc (starts midnight commander and calls the screen 'filemanager')

Check what processes are running
command: ps  fwux
description:
 * shows your current processes running on the server
 * 'f' shows a process tree so that you can tell easily which processes are the parents and child processes
 * 'w'  wraps the text output so that you can see the process name and command line options that were specified
 * 'u' shows username owning the process and some stats
 * 'x' list all processes owned by you
 * adding 'a' will show all processes running on the system

Terminate a process
command: kill -HUP <pid>  or  kill -9 <pid>
description:
  * Use this command to kill a process that you cannot quit normally. <pid> can be found using the ps command.
  * 'HUP' sends the hang up signal, the process should try to quit normally
  * '9' sends a '-KILL' signal ('9' is faster to type), which will forcefully end a process. This is useful if you cannot end a program even with the '-HUP' signal.

List top running processes
command: top
description:
  * shows what processes are using the most resources. use 'q' to quit; 'u' to show a specific username

Make a command share system resources fairly
command: nice <command>
description:
  * runs a command with adjusted scheduling so that it does shares resources with other process more fairly

Make an existing process share system resources fairly
command: renice +<0 to 20> <pid>
description:
  * allows you to 'nice' a process that is already running (make it 'nicer')

Display file contents
command: cat <file>
description:
  * displays the entire file contents on the screen

Display file contents one page at a time
command: less <file>
description:
  * shows the contents of a (text) file one page at a time

Search for text strings in a file
command: grep -i <pattern> <file>
description:
  * search through <file> for <pattern>, matched lines will be displayed
  * 'i' means ignore case (match upper or lower characters)




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