Wednesday, December 15, 2010

Basic Linux Command-line Tips and Tricks - Part 1

40 Basic Linux Command-line Tips and Tricks:
  1. Everything in Linux is a file including the hardware and even the directories.
  2. # : Denotes the super(root) user
  3. $ : Denotes the normal user
  4. /root: Denotes the super user’s directory
    /home: Denotes the normal user’s directory.
  5. Switching between Terminals

    Ctrl + Alt + F1-F6: Console login
    Ctrl + Alt + F7: GUI login
  6. The Magic Tab: Instead of typing the whole filename if the unique pattern for a particular file is given then the remaining characters need not be typed and can be obtained automatically using the Tab button.
  7. ~(Tilde): Denotes the current user’s home directory
  8. Ctrl + Z: To stop a command that is working interactively without terminating it.
  9. Ctrl + C: To stop a command that is not responding. (Cancellation).
  10. Ctrl + D: To send the EOF( End of File) signal to a command normally when you see ‘>’
  11. Ctrl + W: To erase the text you have entered a word at a time.
  12. Up arrow key: To redisplay the last executed command. The Down arrow key can be used to print the next command used after using the Up arrow key previously.
  13. The history command can be cleared using a simple option –c (clear).
  14. cd :   The cd command can be used trickily in the following ways:

    cd : To switch to the home user
    cd * : To change directory to the first file in the directory (only if the first file is a directory)
    cd .. : To move back a folder
    cd - : To return to the last directory you were in
  15. Files starting with a dot (.) are a hidden file.
  16. To view hidden files: ls -a
  17. ls: The ls command can be use trickily in the following ways:

    ls -lR : To view a long list of all the files (which includes directories) and their subdirectories recursively .

    ls *.* : To view a list of all the files with extensions only.
  18. ls -ll: Gives a long list in the following format

    drwxr-xr-x 2 root root 4096 2010-04-29 05:17 bin where

    drwxr-xr-x : permission where d stands for directory, rwx stands for owner privilege, r-x stands for the group privilege and r-x stands for others permission respectively.

    Here r stands for read, w for write and x for executable.
    2=> link count
    root=> owner
    root=> group
    4096=> directory size
    2010-04-29=> date of creation
    05:17=> time of creation
    bin=> directory file(in blue)

    The color code of the files is as follows:
    Blue: Directory file
    White: Normal file
    Green: Executable file
    Yellow: Device file
    Magenta: Picture file
    Cyan: link file
    Red: Compressed file

    File Symbol
    -(Hyphen) : Normal file
    l=link file
    b=Block device file
    c=character device file
  19. Using the rm command: When used without any option the rm command deletes the file or directory ( option -rf) without any warning. A simple mistake like rm / somedir instead of rm /somedir can cause major chaos and delete the entire content of the /(root) directory. Hence it is always advisable to use rm command with the -i(which prompts before removal) option. Also there is no undelete option in Linux.
  20. Copying hidden files: cp .* (copies hidden files only to a new destination)

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