How to Use fgetc in C: Read Characters from a File

In C, fgetc reads the next character from a file stream and returns it as an int. You use it by passing a FILE* pointer opened with functions like fopen. It returns EOF when the end of the file is reached or an error occurs.

Syntax

The fgetc function reads one character from the given file stream and returns it as an int. If it reaches the end of the file or an error happens, it returns EOF.

• FILE *stream: A pointer to the file opened for reading.
• Returns: The next character as an int, or EOF on end of file or error.

c

int fgetc(FILE *stream);

Example

This example opens a text file named example.txt, reads it character by character using fgetc, and prints each character to the screen until the end of the file.

c

#include <stdio.h>

int main() {
    FILE *file = fopen("example.txt", "r");
    if (file == NULL) {
        perror("Error opening file");
        return 1;
    }

    int ch;
    while ((ch = fgetc(file)) != EOF) {
        putchar(ch);
    }

    fclose(file);
    return 0;
}

Output

Hello, world!
This is a test file.

Common Pitfalls

• Not checking if the file was opened successfully before calling fgetc.
• Using char type to store the result of fgetc can cause errors because fgetc returns an int to distinguish EOF.
• Not handling EOF properly can lead to infinite loops or reading invalid data.

c

#include <stdio.h>

int main() {
    FILE *file = fopen("example.txt", "r");
    if (file == NULL) {
        perror("Error opening file");
        return 1;
    }

    // Wrong: using char to store fgetc result
    // char ch;
    // while ((ch = fgetc(file)) != EOF) {
    //     putchar(ch);
    // }

    // Right: use int to store fgetc result
    int ch;
    while ((ch = fgetc(file)) != EOF) {
        putchar(ch);
    }

    fclose(file);
    return 0;
}

Quick Reference

fgetc Cheat Sheet:

Usage	Description
fgetc(file)	Reads next character from file stream
Returns int	Character read or EOF if end or error
Use int ch = fgetc(file);	Store result in int to detect EOF
Check file != NULL	Ensure file opened before reading
Loop with while ((ch = fgetc(file)) != EOF)	Read until end of file

Key Takeaways

Always store the result of fgetc in an int to detect EOF correctly.

Check if the file opened successfully before using fgetc.

Use a loop with fgetc to read characters until EOF is reached.

fgetc reads one character at a time from the file stream.

EOF signals the end of the file or an error during reading.