How to sort a text file in C?

Question

C++ / C#

Hello, how can I make it so that a text file is sorted. I have a variable which is sorted by the bubble sort method. It is necessary that instead of a variable there would be a text file and every time when you enter the command ( ./sort > number.txt ) it sorts those numbers that are inside. Here is the code from where I took https://github.com/hathix/cs50-section/blob/master... , and here's how it is with me
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