getc() Function

The getc() function in C is used to read a single character from a given input stream. It reads the character at the stream’s current position and then advances the internal file position indicator. This function can return a valid character (promoted to an int) or the special value EOF when the end-of-file is reached or an error occurs.

Syntax of getc()

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int getc(FILE *stream);

Parameters

ParameterDescription
streamPointer to a FILE object that identifies the input stream.

It is important to note that because getc() may be implemented as a macro, the stream expression should be free of side effects.

Return Value

On success, getc() returns the character read from the stream (promoted to an int). If the end-of-file is reached or a read error occurs, it returns EOF and sets the appropriate indicator for the stream.

Examples for getc()

Example 1: Reading a Single Character from a File

This example demonstrates how to open a file sample.txt and use getc() to read its first character.

Program

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#include <stdio.h>

int main() {
    FILE *fp = fopen("sample.txt", "r");
    if (fp == NULL) {
        printf("Error opening file.\n");
        return 1;
    }

    int ch = getc(fp);
    if (ch != EOF) {
        printf("First character: %c\n", ch);
    } else {
        printf("Reached end-of-file or error occurred.\n");
    }

    fclose(fp);
    return 0;
}

Explanation:

  1. The file sample.txt is opened in read mode.
  2. getc() reads the first character from the file.
  3. If a character is read successfully, it is printed; otherwise, an error message is displayed.
  4. The file is closed after the operation.

Program Output:

First character: H

Example 2: Reading Characters Until End-of-File

This example illustrates how to continuously read characters from a file using getc() until the end-of-file is reached.

Program

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#include <stdio.h>

int main() {
    FILE *fp = fopen("sample.txt", "r");
    if (fp == NULL) {
        printf("Error opening file.\n");
        return 1;
    }

    int ch;
    while ((ch = getc(fp)) != EOF) {
        putchar(ch);
    }

    fclose(fp);
    return 0;
}

Explanation:

  1. The file sample.txt is opened in read mode.
  2. A loop uses getc() to read each character until EOF is encountered.
  3. Each character is printed immediately using putchar().
  4. The file is closed after reaching the end-of-file.

Program Output:

Example 3: Handling End-of-File and Error Conditions

This example demonstrates how to handle cases when a file cannot be opened or when getc() returns EOF due to an error or end-of-file condition.

Program

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#include <stdio.h>

int main() {
    FILE *fp = fopen("nonexistent.txt", "r");
    if (fp == NULL) {
        printf("Error: Unable to open file.\n");
        return 1;
    }

    int ch = getc(fp);
    if (ch == EOF) {
        if (feof(fp)) {
            printf("End-of-file reached.\n");
        } else if (ferror(fp)) {
            printf("Read error occurred.\n");
        }
    }

    fclose(fp);
    return 0;
}

Explanation:

  1. An attempt is made to open the file nonexistent.txt in read mode.
  2. If the file does not exist, an error message is printed and the program exits.
  3. If the file were open but getc() returned EOF, the program would check whether it was due to end-of-file or a read error.

Program Output:

Error: Unable to open file.