README.md

Bashgenn

Bashgenn - the Bash script generator for text maniputaion.

Bashgenn is a simple programming language for text manipulation.

Installation

Bashgenn can be installed from RAPR (Debian/Ubuntu only, make sure you have RAPR set up first):

sudo apt-get install bashgenn

On other operating systems, use the install script:

curl -s https://tinyurl.com/bginst3-linux | bash

Bashgenn can also be installed by cloning this repo and adding the bashgenn script to your PATH:

git clone https://github.com/romw314/bashgenn
cd bashgenn
cp bashgenn ~/.local/bin/

Or install it per-machine:

git clone https://github.com/romw314/bashgenn
cd bashgenn
sudo cp bashgenn /usr/local/bin/

Tutorial

Bashgenn scripts always read from standard input and write to standard output. They don't have any other input or output.

Bashgenn scripts are created from commands. Each command has it's own line in our file and must be written UPPERCASE. Each command can have up to 2 arguments, separated by spaces.

There are also variables. Variables does not have their types, they are always strings (or numbers stored as strings).

The most basic commands in Bashgenn are PROG_INIT, DECLARE, READ and ECHO.

PROG_INIT must always be placed at the beginning of the script.

DECLARE initializes a variable with an empty string. DECLARE takes one argument - the variable name to initialize. Variables cannot be used before initialized.

READ reads one line of input and saves it to a variable. READ takes one argument - the name of the variable to save the input in.

ECHO writes data from a variable to the output. ECHO takes one argument - the name of the variable to write the data from.

Here is a basic script which reads one line and prints it out:

PROG_INIT
DECLARE our_variable
READ our_variable
ECHO our_variable

We can compile and run the script by saving it into a file named our_script.bgn and running the following commands:

bashgenn our_script.bgn
./bg-f

Please note that Bashgenn always saves the output script to a file named bg-f. There's no option to change the output file. It also can't compile the script to a binary, it compiles it only to a Bash script.

We can also write the text three times:

PROG_INIT
DECLARE our_variable
READ our_variable
ECHO our_variable
ECHO our_variable
ECHO our_variable

And if we want to write the text 500 times? Should we add the ECHO command 500 times? No! The REPEAT command is designed for that:

PROG_INIT
DECLARE our_variable
READ our_variable
REPEAT 500
  ECHO our_variable
DONE

We can also read and write out two lines:

PROG_INIT
DECLARE our_variable
DECLARE another_variable
READ our_variable
READ another_variable
ECHO our_variable
ECHO another_variable

Now, it's time for practice. Adapt the code above to write the two lines in reversed order. When we enter this input:

Hello
World

The output should be:

World
Hello

Click to expand the solution

PROG_INIT
DECLARE our_variable
DECLARE another_variable
READ our_variable
READ another_variable
ECHO another_variable
ECHO our_variable

How to write a script that just prints Hello, World!, without any input? The CONST_SET command and the CONST_WRITE command are designed for that. We create a constant (not a variable) and copy it to a variable. Then, we write out the variable. Please note that we need to add _OPT ireq true before PROG_INIT in order to use CONST_WRITE.

_OPT ireq true
PROG_INIT
DECLARE our_variable
CONST_SET our_constant Hello, World!
CONST_WRITE our_constant our_variable  
ECHO our_variable

In bashgenn lines starting with - are comments, for example:

PROG_INIT
- This is a comment,
- comments are ignored
- by the compiler.

- This script does not do anything.

Next, we'll try to reverse a string (for example olleh from hello):

- This script is slow because we reverse the string character by character.
PROG_INIT

- Initialize variables
DECLARE last
DECLARE input
DECLARE result

- Read the input into a variable named `input`
READ input

- STRGET repeats the commands inside until the variable in the first argument
- (in this case `input`) is not an empty string.
STRGET input
  - This command removes the last character from the variable `input`
  - and saves it in the `last` variable.
  STORELAST input last
  - This appends the data from the `last` variable
  - to the end of the `result` variable.
  - Please note that the variable is empty at the beginning.
  STRCAT last result
DONE

- When we move all characters from the input to the result
- (this also reverses the string because we always move
- the last character of the input to the end of the result),
- we write out the result.
ECHO result

If you want to write to a file, you need to use BgBase - a library for Bashgenn. Bashgenn scripts without BgBase read only from standard input and write to standard output.

After installing BgBase, you can write Hello, world! to a file named hello.txt using this script:

- This is needed if you want to import modules.
MODULE main
- This is needed for CONST_WRITE.
_OPT ireq true
PROG_INIT
- This imports the io module from BgBase.
IMPORT io

- Set the filename. The filename must be in the bgfile variable. No other variable names work.
CONST_SET filename hello.txt
CONST_WRITE filename bgfile

- Set the data to write to the file. The data must be in the bgdata variable.
CONST_SET our_data Hello, world!
CONST_WRITE our_data bgdata

- This writes to the file. You need to set the bgdata and the bgfile variable before this.
- The io module must be imported.
USE io.writefile