Create Linux Bash and Windows batch scripts simultaneously with Batsh

Mixed Doubles

© Lead Image © andreykuzmin, 123RF.com

© Lead Image © andreykuzmin, 123RF.com

Article from Issue 171/2015
Author(s):

Batsh kills two birds with one stone: Programs written in this language can be compiled both as Linux Bash scripts and Windows batch files.

Linux users like to use Bash scripts to automate repetitive tasks. In the Windows world, batch (.bat) files are used in the same way. However, the commands used in Linux and Windows scripts are often significantly different. Those who work in both Linux and Windows environments therefore not only have to create and maintain two separate scripts, they also have to grapple with various cryptic instructions.

However, this situation should end soon. Google employee Carbo Kuo, a Chinese native living in Switzerland, is currently working on a programming language called Batsh, whose code is translated by a compiler into the appropriate Bash or batch script.

Welcome Ritual

The following line in Batsh will suffice to output the popular message Hello world!:

println("Hello world!");

You can see for yourself what the compiler makes of this on the Batsh compiler website [1]: Type the line in the text box on the left and then click on Compile to Bash. The web page then compiles the Batsh programming code and displays an equivalent Bash script on the right-hand side. In this case, you see the line:

"echo" "-e" "Hello world!"

To generate a batch file for Windows, click on Compile to Windows Batch. Figure 1 shows the results for the Hello World example. The text box on the left-hand side supports various functions when inputting programming code, such as color highlighting and automatically closing parentheses.

Figure 1: The Hello World batch script. A few sample scripts can be obtained via Examples, and clicking About Batsh takes you to its GitHub page.

If you want to work with Batsh, you should have at least some experience writing small Bash scripts or programming in another language, because the documentation only consists of a very short and still incomplete reference [2].

Fast Learner

Batsh is based to some extent on the C programming language, but it gives you the freedoms of a scripting language. Listing 1 shows a simple sample script that pieces together the file name, photo1.tiff, from individual parts.

Listing 1

Batsh Example

number = 1;
prefix = "image";
filename = prefix ++ number ++ ".tiff";
// this is a comment
println(filename);

First, the variable number stores the number 1 . As in C, each instruction ends with a semicolon. The second line then stores the text image in the variable prefix. Character strings must always be in double quotes; single quotes are not allowed in Batsh. The ++ operator in the third line concatenates two strings. The file name photo1.tiff is thus stored in the variable filename. Finally, the last line outputs the complete file name. As in C or Java, you can initiate comments with two forward slashes. The complied Bash script is shown in Figure 2.

Figure 2: In the Bash script, the Batsh compiler puts many elements in quotation marks.

Frequently used command sequences can be packaged in a function. Figure 3 shows a simple example. The notation should be familiar to programmers of Bash scripts: The name of the function follows the function keyword. All instructions to be executed by the function follow in curly brackets. In Figure 3, function filename only outputs one piece of text. Finally, the last line calls up the function and thus the instructions contained in it.

Figure 3: On the left, the definition of a function in Batsh; on the right, the equivalent in Bash.

In the Front, Out the Back

Parameters can be passed into the function using parentheses. Listing 2 illustrates how this works: When you call the filename function, the number 1 ends up in the num variable, and the end variable holds .png. These two variables are then available in the function.

Listing 2

Passing Parameters

function filename(num, end) {
  file = "image" ++ num ++ end;
  return file;
}
dn = filename(1, ".png");
println(dn);

The filename function then assembles a file name; however, this time it does not write this to the screen with println(); instead, it returns the name to the calling function, which receives the filename in the dn variable and displays the return value in the last line. For more on displaying output, see the "Printed" box.

Printed

The Batsh println() function has a sibling named print() that also displays the text you pass in at the command line; however, it does not use a newline between the elements. Both functions support any number of parameters. The following example outputs the text Hello World:

a="World";
print("Hello ", a);

An alternative to print() is the undocumented echo(). The Batsh compiler translates print() to "echo" "-ne"; however, it translates the echo() function to just "echo".

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