Fundamental of Computing Week 9: 9 October to 15 October (Basic Commands in Linux)

 Basic Commands in Linux


Introduction

  • Commands are known as 'programs' as when you run a command, the accompanying program code, written for the command, is executed.
  • File management in Linux becomes easy if the right commands are known.

Linux Commands

  • In Linux commands:
    •     Blue is used to indicate directories.
    •     White is used to identify files.
    •     Similar color schemes are used in different distribution of Linux.
    •     Commands are case-sensitive.
  • ls command is used to see the list of files on Linux or UNIX system.
  • ls-R command is used to show all the files not only in directions but also subdirectories.
  • ls-al command is used to give detailed information about the file in a column format.

Listing Hidden Files

  • ls-a command is used to access hidden files.
  • Hidden items in UNIX/Linux begin with a '.' period symbol at the beginning of the file and directory.
  • Any directory or file beginning with a '.' will be ignored until explicitly requested.

Creating and Viewing Files

  • The cat- command displays text files. It can also be used to duplicate, combine and create new text files.
  • To create a new file, use the command:
    • cat>filename
    • Add content
    • Press 'ctrl + d' return to command prompt
  • To view a file, use the command cat.
  • To specify, use the command cat filename.
  • To combine two files, use the command cat file1 file2 > newfilename

Deleting Files

  • The rm command removes files from the system without requiring confirmation.
  • To make sure a file is removed or not we can check using the ls command after deletion.
  • The mv command is used to move a file to different directory.
  • The mv command requires superuser/root user privileges.
  • Regular users can run programs with the security rights of the superuser/root user by using the sudo program.


Moving and Files

  • To use the sudo program, the sudo command requires password authentication.
  • The password given for sudo is saved for 15 minutes per termnal by default and it avoids the need to repeatedly enter the password
  • Following authentication, the system will execute requested command.
  • Sudo keeps a record of every command executed.
  • System administrators can hunt down the person responsible for unfavorable system changes.

Re-Naming Files

  • The command mv can also be used to rename a file.
  • The syntax is mv filename newfilename.

Directory Manipulation

  • The command mkdir is used to create directories.
  • It creates a subfolder in the current working directory, which is normally the 'Home Directory'.
  • mkdir mydirectory is the syntax.
  • To create a directory in a place other than the 'Home directory' i.e., create a directory 'file' under '/tmp' directory, we can use the command mkdir/tmp/file.
  • You can also create multiple directories at a time.

Removing Directories

  • The command rmdir is used to remove a directory.
  • For example, rmdir file will delete the directory named file.
  • Make sure there are no files or subdirectories in the directories in the directory you wish to delete. Before deleting the parent directory, delete the files/subdirectory.

Renaming Directories

  • The command mv can also be used for renaming directories.
  • The syntax for the mv command is oldfilename newfilename.

Search Command

  • grep (global regular expression print) is a command that searches files for text that matches a given pattern and prints it.
  • The regular expression can be used to define the pattern.
  • You can use the command <man grep>
  • The command find is used to search files and directories.

Other Important Commands

  • The command history is used to display all commands used in the past for the current terminal session.
  • This command helps the user to refer to previously submitted commands and re-use them.
  • The command clear is used to remove all terminal clutter and have a clean window to work in.


Text Editor

  • vi (Visual Editor) or vim (Visual Editor Improved) is a terminal-based text editor that can be used to create any type of file.
  • The command <vi> or <vim> to work with it.
  • A text editor called nano that is built-in the vi/vmi.
  • A built-in software named gedit is present if you want to use the GUI based text editor.
  • The command <geidit> is used to launch it.
  • The command <gedit file_name> is used to open the file in gedit.




















 






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