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C Program to count number of lines in a file

Last Updated : 29 Dec, 2022
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C
/* C Program to count the Number of Lines in a Text File */
#include <stdio.h>
#define MAX_FILE_NAME 100

int main()
{
    FILE *fp;
    int count = 0; // Line counter (result)
    char filename[MAX_FILE_NAME];
    char c; // To store a character read from file

    // Get file name from user. The file should be
    // either in current folder or complete path should be provided
    printf("Enter file name: ");
    scanf("%s", filename);

    // Open the file
    fp = fopen(filename, "r");

    // Check if file exists
    if (fp == NULL)
    {
        printf("Could not open file %s", filename);
        return 0;
    }

    // Extract characters from file and store in character c
    for (c = getc(fp); c != EOF; c = getc(fp))
        if (c == '\n') // Increment count if this character is newline
            count = count + 1;

    // Close the file
    fclose(fp);
    printf("The file %s has %d lines\n ", filename, count);

    return 0;
}

Output:

Enter file name: countLines.c
The file countLines.c has 41 lines

Time complexity: O(N) where N is total number of characters in given file

Auxiliary space: O(1) because it is using constant space for variables and array filename


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