Linux Shell

This is a Unix shell program
A shell is simply a program that conveniently allows you to run other programs This shell supports the following commands:

1. The internal shell command exit which terminates the shell
2. A command with no arguments
   • Example: ls, cp, rm
   • System calls: fork(), execvp(), exit(), waitpid()
3. A command with arguments
   • Example: ls –l
4. A command, with or without arguments, executed in the background using &.
   • Example: gedit &to run in the background or gedit to block terminal until finish
   • Details: In the case of gedit &, the shell must execute the command and return immediately, not blocking until the command finishes.
   • Concepts: Background execution, signals & signal handlers
5. Shell builtin commands
   • Commands: cd & echo
   • Details:
     cd ~
cd ..
cd <absolute_path>
cd <relative_path_to_current_working_directory>
echo "wow" => wow
     export x=5
echo "Hello $x" => Hello 5
     
6. Expression evaluation
   • Commands: export
   • Details: Set values to variables and print variables values. No mathematical operations is needed.
   • Export Details: Accept input of two forms, either a string without spaces, or a full string inside double quotations.
   • Example:
     export x=-l
ls $x => Will perform ls -l
export y="Hello world"
     echo "$y" => Hello world