CRASH

Crazy Random Awesome SHell

CRASH is a C++ based shell that provides an interface to execute commands. Commands can be executed from either a user Interactive Mode or a script file in Batch Mode.

Prerequisites

• make
• g++

Installation

• Clone this repo
• Open the workspace in a terminal
• Use make commands to build

Make Targets:

make target	description
main	Builds the main executable
test	Builds the test executable
run	Runs the main executable
run-test	Runs the test executable
clean	Clean build files from the project

Usage

The program can be used in two major ways:

Interactive mode

Type external or internal commands directly into CRASH.

# Internal Command
CRASH $ history -l 5


# External Command
CRASH $ lsblk

Batch Mode

To run a script in batch mode, there are 3 possible options.

Executable Script

• Give the script a path to CRASH by including #!PATHTOCRASH
  • For example, use #!./bin/main if inside CRASH's directory, or if inside CRASH's test directory use #!../bin/main.
• Make the script executable by using chmod +x SCRIPTNAME
• Run the script ./SCRIPTNAME or SCRIPTNAME

Stdin Piping

• Create a script and run ./bin/main < [script location]

Script by Name

• Create a script and run ./bin/main [script location]

Character Usage

Meta Characters

Character	Usage
\	Continuation
#	Comment
;	Split line
>	Store
>>	Append
<	Redirect
2>	Store Error
2>>	Append Error

Meta Character Usage

• \ Use backslack to continue a line
• # Use hashtags to add comments
• ; Use semicolons to seperate lines to run multiple commands at once.
  • To run both the external lsblk and lscpu commands.
  • CRASH $ lsblk ; lscpu
• > Use a single greater than character to store the output from a command into a file.
  • To store the output of lscpu to a file called output.txt
  • CRASH $ lscpu > output.txt
• >> Use two greater than character to append the output from a command to a file.
  • To append the output of lsblk to a file called output.txt that already has existing content.
  • CRASH $ lsblk >> output.txt
• | Use a vertical bar to pipe the output of one program to another.
  • To pipe the output of lscpu to sort to have the output in alphabetical order.
  • CRASH $ lscpu | sort
• < Use a less than character to redirect the input of program to a file.
  • To display the contents of a file called test5.txt
  • CRASH $ cat < test5.txt

Wild Card Character Matching

Wild cards can be used to find matching files in the current working directory.

• Question marks (?) can be used to match any single character in a file name.

  • Example: tes?.txt can be matched to test.txt

• Asterisks (*) can be used to match any number of characters in a file name.

  • Example: t*.txt can be matched to test.txt

• Square brackets ([...]) can be used to match the characters inside the bracket.

  • Example: test[0-9].txt can be matched to test5.txt

Wildcards can be also be combined with meta characters for advanced functionality.

• To store the names of all files in the current directory to output.txt
• CRASH $ echo * > output.txt