Скачать или смотреть How to Invoke Code Between EOF ... EOF Using call system in gfortran

Learn how to utilize gfortran's `call system` to run embedded code between ` EOF ... EOF` for effective plotting with gnuplot, without needing external scripts.
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Harnessing gfortran to Invoke Code with call system for Gnuplot

In the world of Fortran programming, particularly when working with data visualization tools like Gnuplot, a common challenge arises: how can you effectively invoke commands that are nested within an embedded format like <<EOF ... EOF? This precise question often leads developers to seek out solutions that utilize call system in gfortran for executing code seamlessly. In this guide, we will delve into a detailed explanation of this process, providing you with organized insights and context for a thorough understanding.

The Problem: Executing Commands between <<EOF ... EOF

When plotting data using Gnuplot in a Fortran program, you may want to send commands directly within your code without relying on separate plot scripts (like .plt files). The goal here is straightforward: invoke Gnuplot commands effectively to plot your data present in a simple text file, such as salida.txt, without any intermediate file creation. Below is a general example of what you're trying to achieve:

[[See Video to Reveal this Text or Code Snippet]]

This command sequence utilizes embedded block strings, or here-documents, to maintain clarity in your scripts.

The Solution: Implementing call system in gfortran

You can achieve the desired functionality using a structured gfortran program. Here's how you can implement this using the call system approach:

Step 1: Define Your Fortran Program

To achieve the intended functionality, you will need a basic structure for your Fortran program like this:

[[See Video to Reveal this Text or Code Snippet]]

Key Components of the Code

String Concatenation: The // operator is used for concatenating strings, allowing for neat organization of your command.

Line Continuation: The & symbol signifies line continuation, ensuring the command remains intact over multiple lines.

Executing the Command: The call EXECUTE_COMMAND_LINE(command) effectively sends the entire command block to Gnuplot for execution.

Alternative Method: Using GNU Extensions

If you're open to using GNU-specific extensions, you can customize your code further by utilizing -fbackslash during compilation. This allows the use of \n for line breaks and removing concatenation. Here's how that looks:

[[See Video to Reveal this Text or Code Snippet]]

Notes:

The \n character replaces the need for new_line('A') and improves readability.

The & at the beginning of a line allows for continuity when breaking across lines while keeping your string cohesive.

Conclusion

Utilizing gfortran to invoke code between <<EOF ... EOF using call system for Gnuplot plotting is a highly efficient method for visualizing data. With the right understanding of string manipulation and execution commands, you can integrate powerful visualization capabilities directly into your Fortran programs.

Should you encounter any issues, refer back to the provided examples and tweak the string constructions as needed. Happy coding and plotting!