bash Command in Linux

Syntax of bash Command in Linux

The basic syntax of the bash command in Linux is as follows:

Where:

• options: These are optional flags that modify the behavior of the bash command. For example, '-c' allows you to pass a command directly to bash as a string.
• command_file: This is an optional argument specifying a script file that bash will execute.
• arguments: These are additional parameters or arguments that will be passed to the command_file if one is specified.

Options in bash Command in Linux

1. -c: Read and execute commands from the following string.

   For example -

   Output:

   This command makes bash execute the 'echo' command, which prints 'Hello, World!' to the console.

2. -i: Start an interactive shell. This is typically used when starting bash from a script.

   For example -

   This command starts a new interactive bash session. The output will vary based on your system configuration.

3. -s: Read commands from the standard input. This is often used in conjunction with piping.

   For example -

   Output:

   This command first 'echoes' a string containing a bash command, then pipes this string to bash which executes it.

Example Usages

• Executing a bash script file:

  Explanation: This usage runs the script.sh file in the bash shell. The output will depend on the contents of script.sh.

• Starting a new bash session:

  Explanation: This command starts a new instance of the bash shell. The output will be a new command prompt.

Advanced Use Cases of bash Command in Linux

• Running a command with a delay:

  Output:

  Explanation: This command makes bash execute two commands in sequence. First, it waits for 5 seconds using the 'sleep' command, then it prints 'Hello, World!'. The output is delayed by 5 seconds.

• Running multiple commands at once:

  Output:

  Explanation: This command makes bash execute two commands concurrently. The ampersand (&) tells bash to run the preceding command in the background, allowing the following command to run immediately. The output is both 'Hello, World!' and 'Goodbye, World!' almost simultaneously.

• Reading commands from a file:

  Output:

  Explanation: This command first creates a file named 'commands.txt' and writes a bash command to it. Then, it uses bash to execute the commands in the file. The output is 'Hello, World!'.