Frequently Asked Question

Linux commands are powerful tools that allow users to interact with the operating system through a terminal. Each command typically follows a simple structure: the command itself, followed by optional or mandatory arguments, and sometimes options or flags to modify the behavior of the command. For example, the ls command, which lists directory contents, can be enhanced by adding the -l option to display detailed information about each file. To make it easier to learn and use these commands, most come with a built-in help option. By using the -h or --help flag, users can quickly access a detailed description of the command, its syntax, and available options.

For example, to learn more about the ls command, you can type:

ls --help

or

ls -h

This will display information on how to use the command, including optional flags like -l for detailed listing and -a to show hidden files. This makes the -h or --help options a valuable resource for users exploring new commands or looking for additional options.

1. Print Working Directory: pwd

The pwd command stands for "print working directory." It displays the full path of the current directory you are working in. It is particularly helpful to ensure you are in the right directory before running any other commands.

Example:

In this example, the pwd command shows that the current directory is /home/hpctech.

2. List Directory Contents: ls

The ls command is used to list the files and directories of the current or any other directory. It offers several options to display additional information about the files and directories.

ls [options] [directory]

Common options:

• -l: List detailed information, including file permissions, size, and modification date.
• -a: Show hidden files (files starting with a dot .).
• -h: Display sizes in a human-readable format (e.g., KB, MB).

Example 1:

The above command lists the files in the current directory with detailed information. The -lh options display the sizes in a readable format.

Example 2:

The above command lists the files in Jupyter directory with detailed information.

3. Change Directory: cd

The cd command is used to navigate between directories in the Linux file system. It is an essential command to navigate through directories and files you need to work with.

cd [directory]

Example:

• The first command changes the directory to the /home/hpctech/Jupyter directory.
• The second command, cd .., moves one level up (to the parent directory).
• The third command, cd ~, moves to the home directory.

4. Copy Files and Directories: cp

The cp command allows you to copy files or directories from one location to another.

cp [source] [destination]

Common options:

• -r: Recursively copy directories (needed when copying a directory with its contents).

Example:

• The first command copies job.pbs to the /home/hpctech/ directory.
• The second command recursively copies all contents from Jupyter to Jupyter_new

5. Remove Files and Directories: rm

The rm command is used to permanently delete files and directories. 

Caution: Use it carefully, especially with the -r and -f options.

rm [options] [file/directory]

Common options:

• -r: Recursively remove directories and their contents.
• -i: Prompt for confirmation before removing each file (recommended).
• -f: Force deletion without confirmation.

Example:

• The first command deletes job.pbs.
• The second command recursively removes the Jupyter_new directory and all its contents.

6. Make Directory: mkdir

The mkdir command creates new directories sub-directories in the file system to organize your data.

mkdir [directory_name]

Example:

• The first command creates a new directory named new_dir
• The second command uses the -p option to create a directory and its parent directories if they don’t already exist.

7. Remove Directory: rmdir

The rmdir command is used to remove empty directories. It won’t remove directories that contain files or subdirectories. If you need to remove non-empty directories, you’ll need to use rm -r instead of rmdir.

rmdir [directory_name]

Example:

This command will remove the empty_dir directory, but only if it has no contents.