How to Access an Inputted File in C Using Standard Input

Discover why inputted files don’t appear in `argv` and learn how to read them using standard input in your C programs.
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How to Access an Inputted File in C Using Standard Input

When you are programming in C, one common task is to read from files or standard input. If you've ever tried running a program in C that looks something like this:

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Understanding argv and File Redirection

What is argv?

In C, when you define your main function as follows:

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argc is the argument count, which tells you how many arguments have been passed to your program.

argv is an array of strings (character pointers) representing the actual arguments. The first element argv[0] is always the program name, followed by any additional command-line arguments.

Where is the Input File?

Reading Input from Files in C

Using fgets to Access Input

To read the contents of the file you’ve redirected, you can utilize standard input functions in C. One common option is fgets(), which reads a line from stdin. Here’s how you can implement this:

Example Code

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Explanation of the Code

Print Command-Line Arguments: Initially, we loop through argv to print all the command-line arguments received.

Create a Buffer: We define a character array buffer that temporarily holds each line from the input.

Read and Print: The while loop uses fgets() to read from stdin and prints the lines using puts() until there are no more lines to read.

Conclusion

Understanding how to access an inputted file in a C program is crucial for efficient data handling. By utilizing standard input from redirection, you can read any file seamlessly as if it were a part of your input during runtime. With the provided code example, you should be able to read from files redirected into your C programs easily. Try experimenting with different files and structures as you continue to enhance your coding skills!

Feel free to ask any questions if you need further clarifications or examples related to file handling in C!