Automate Fortran Input Parameters in Bash Script with Here Strings

Learn how to run a Fortran program with multiple input parameters using Bash. This guide will help you automate the process efficiently.
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Automate Fortran Input Parameters in Bash Script

Running a Fortran program that requires multiple input parameters can be a tedious task, especially if the program interacts with the user for every input. In such cases, it’s essential to find an efficient way to automate this process using a Bash script. In this guide, we will explore how to provide multiple parameters to a Fortran program seamlessly through Bash scripting.

Understanding the Problem

You might have encountered a situation where your Fortran program interacts and asks for inputs one at a time. If you have to run this multiple times with different input parameters, doing it manually can be a hassle. Fortunately, you can automate this process by creating a simple Bash script that feeds the inputs to the program without user interaction.

The Challenge

You initially tried to create a Bash script with the following:

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However, this approach led to the problem where the entire input string got interpreted as a single parameter rather than individual inputs. The key here is understanding how Bash interprets strings and newlines.

The Solution

Method 1: Correctly Using Dollar Sign Ending Quotes

One effective way to format the input string correctly is by using the $'...' quoting style which enables the embedding of literal newlines (denoted as \n) in your string. Here’s how you can do it:

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This method ensures that inputstr contains each parameter separated by an actual newline, allowing the Fortran program to read them properly.

Method 2: Using Quotation Marks for Multiline Inputs

Alternatively, you can avoid using the $'...' syntax altogether. Instead, you can use regular double quotes to handle the variables and let Bash recognize each line as a separate input:

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Method 3: Using Here Document Syntax

Finally, for cases where you want clarity and direct usage without variable manipulation, you can opt for a Here Document (HereDoc). This method is particularly useful for more extensive scripts or when you prefer to write inputs directly in a block format:

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This method writes the inputs directly to the program, making it easy to read and modify.

Conclusion

By utilizing any of these methods, you can efficiently automate the input process for your Fortran programs using Bash scripts. Whether you prefer the clarity of Here Documents, the flexibility of dollar sign ending quotes, or multiline double quoting, each approach simplifies the way you interact with your software, saving you time and effort. Start automating your Fortran inputs today, and elevate your coding efficiency!