Simple Unix Command Interpreter

This program emulates a Unix shell and allows users to run linux commands directly in it.

Compilation

To compile this program using the gcc compiler, run this command

• Manually

$ gcc -Wall -pedantic -Werror -Wextra -std=gnu89 *.c -o hsh

• Using make This feature enables easy compilation of the program. Simply run this command. $ make

Usage

Interactive

The interactive mode allows users to infinitely run Unix commands until a termination signal is sent to the program: CTRL + C. To use it interacitively, start the program thus:

$ ./hsh

Sample

You can run a command with or without argumeents. Example, the ls

($) ls /
bin   etc   lib32   lost+found  myproject  root  snap  tmp      var
boot  home  lib64   media       opt        run   srv   usr
dev   lib   libx32  mnt         proc       sbin  sys   vagrant


($) touch play_1 play_2 play_3
($) ls
play_1 play_2 play_3

Non-interacitive

This simple unix command interpreter can equally be used non-interaactively by piping the output of a program into it. Example, to list all the files in the current working directory:

$ echo "ls" | ./hsh

General features

• Can handle command lines with arguments
• Handled the PATH
• Implemented the exit built-in, that exits the shell Usage: exit [status]

($) exit

Quits shell with last exit status.

• Implemented the env built-in, that prints the current environment.
• Implemented the setenv and unsetenv builtin commands setenv: Initialize a new environment variable, or modify an existing one. Syntax: setenv VARIABLE VALUE. Should print something on failure. unsetenv: Remove an environment variable. Syntax: unsetenv VARIABLE. Should print something on failure.
• Implemented the cd builtin command. Changes the current directory of the process. Syntax: cd [DIRECTORY]. If no argument is given to the command, it takes the uesr to HOME directory. To change to the previous command cd -.
• Multiple commands can be entered on the command line, separated by a semi-colon ;. Eg.

($) ls /var; ls /hbtn ; ls /var

• Comments: Everything after a hash # is considered a comment and not part of the command to be executed. e.g

($) ls /var # I am a simple comment :)

Missing features

• Ability to move cursor while in command line
• Aliases
• File input
• Shell variables: E.g. $?, $$.
• Logical operators: E.g. &&, ||.