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Using the command-line editor (shell) II : the very first shell commands to experiment

Table of content :

• Introduction
• Knowing 'where you are'
• Creating an empty file
• To add a line at the end of a file without removing its content
• To read the content of a file
• To replace the content of an existing file with another content or to create a file with a specific content
• To read the content of a file spreading across several pages
• To change the name of a file or a directory
• To create a new copy of a file
• To see what's inside a directory
• To go elsewhere
• To clean up
• To create or remove directories
• To put a file somewhere else
• To look for some text in a file
• To know what is happening right now
• To have a look at what you've done
• To become administrator and quickly go back under your standard identity
• Other resources

Section index - Knowledge Base index

Introduction

If you're a beginner, have fun playing in a console with these first commands.

To open a console :

• Press simultaneously Alt+Ctrl+Fn keys (n being between 1 and 6) : you come back to your classical graphical environment with Alt-F7
• Or click on K Menu -> System -> Terminals and choose, for instance, Konsole.

Be careful not to be logged on as 'root' but as a simple user.

Knowing 'where you are'

• The pwd command displays the name of the working directory (sometimes called current directory).
  To remember more easily : 'pwd' is the acronym of print working directory.

Creating an empty file

• Use the command touch file_name.
  If file_name is an existing file, only its date and hour will be changed, its content will not be modified.

To add a line at the end of a file without removing its content

• A combination between the 'echo' command and the redirection operator '>>' (be careful not to confuse with '>' described below) :
  echo "blah blah blah" >> file_name
  .

To read the content of a file

• The command cat file_name displays the content of a text file.

To replace the content of an existing file with another content or to create a file with a specific content

• Similar to the last-but-one command, but using this time the redirection operator '>' :
  echo "blah blah blah" > file_name
  

(if the file doesn't exist, it will be created, without using the 'touch' command)

To read the content of a file spreading across several pages

• The command less file_name displays the content of a file and allows moving into it.

To change the name of a file or a directory

• The command mv name1 name2 renames the file or directory name1 into name2.

To create a new copy of a file

• The command cp file1 file2 creates file2 by copying the content of file1 into it.

To see what's inside a directory

• The command ls -l lists the content of the working directory.
• The command ls -la lists the content of the working directory and includes hidden files.
• The command ls -l dir lists the content of the 'dir' directory.

To go elsewhere

• The command cd directory changes the working directory.

To clean up

• The command rm file removes a file.

To create or remove directories

• The command mkdir directory creates a directory.
• The command rmdir directory removes an empty directory.

To put a file somewhere else

• The command mv file directory moves the file 'file' to the directory 'directory'.

To look for some text in a file

• The command grep text_to_look_for file_name looks for a text in a file.
• The command grep -i chaine_à_chercher nom_de_fichier does the same thing but do not care about uppercase and lowercase letters.

To know what is happening right now

• The command top lists programs using the most your CPU (they will be up in the display). Use 'q' to quit.
• The command ps ux lists all active programs belonging to the current user.
• The command ps aux lists all active programs in the system.

To have a look at what you've done

• You can recall and see the previous commands you've typed using up and down arrow keys on your keyboard.
• The command history displays a list of the last commands used.

To become administrator and quickly go back under your standard identity

• The command su - switch you to the administrator mode, i.e. you become 'root' (be careful : don't stay under root to experiment all these commands, a mistake can be made very quickly!).
• The command exit bring you back to your previous identity.

Other resources

• How to copy files and folders with the 'cp' command
• How to move files and folders with the 'mv' command
• Searching Text Files With 'grep'
• Some tips for the shell history
• How to customize 'ls' output

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Next page : Auto-Completion ; Commandline History ; Commandline Editing ; Available Shell Shortcuts

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Author : ptyxs (march 2006)