shell24

shell24 is a custom shell program written in C that goes into an infinite loop waiting for user commands. It assembles and executes each command using fork(), exec(), and other system calls as required.

Features

• Infinite Loop: The shell waits for user commands indefinitely.
• Command Execution: Executes user commands using system calls.
• Special Characters Handling:
  • Text File Concatenation (#): Concatenate up to 5 text files.
  • Piping (|): Supports up to 6 piping operations.
  • Redirection (>, <, >>): Supports input/output redirection.
  • Conditional Execution (&&, ||): Supports up to 5 conditional execution operators.
  • Background Processing (&): Execute commands in the background and bring them to the foreground.
  • Sequential Execution (;): Execute up to 5 commands sequentially.

Rules and Conditions

Rule 1

The program/command newt (shell24$newt) must create a new copy of shell24. There is no upper limit on the number of new shell24 terminal sessions that can be opened.

Rule 2

The argc (includes the name of the executable/command) of any command/program should be >=1 and <=5.

Examples

• shell24$ date (argc = 1)
• shell24$ ls -1 -l -t ~/chapter5/dir1 (argc = 5)
• shell24$ cat input1.txt input2.txt (argc = 3)

Rule 3

The argc of individual commands or programs that are used along with the special characters listed below should be >=1 and <=5.

Examples

• shell24$ ls -l -t | wc
  • The first command has argc = 3 and the second command has argc = 1.

Special Characters

• # Text File Concatenation:
  • Example: shell24$ check.txt # new.txt # new1.txt # sample.txt
  • Files are concatenated in the listed order, and the final result is displayed on stdout.
• | Piping:
  • Example: shell24$ ls | grep *.c | wc | wc -w
  • Supports up to 6 piping operations.
• >, <, >> Redirection:
  • Example: shell24$ cat new.txt >> sample.txt
• && Conditional Execution:
  • Example: shell24$ ex1 && ex2 && ex3 && ex4
  • Example: shell24$ c1 && c2 || c3 && c4
• || Conditional Execution:
  • Similar usage as &&.
• & Background Processing:
  • Example: shell24$ ex1 & (runs ex1 in the background)
  • Example: shell24$ fg (brings the last background process to the foreground)
• ; Sequential Execution:
  • Example: shell24$ ls -l -t ; date ; ex1 ;
  • Supports up to 5 sequential commands.

Installation

1. Clone the repository:

   git clone https://github.com/yourusername/shell24.git

2. Navigate to the project directory:

   cd shell24

3. Compile the program:

   gcc -o shell24 shell24.c

Usage

Run the shell:

./shell24