Why is there an extra "?" displayed after executing C program(to read aand display a txt file)

Question

I wrote a C program which reads an existing txt file and outputs the contents inside that file.

The issue I'm having is that it displays a ? at the end.

For example: if the contents in the file(txt) were Hello World!, the terminal displays Hello World!?.

Here is the code:

#include <stdio.h>
#include <stdlib.h>

int main()
{
    FILE * fp;
    char ch;
    char filename[100];
    char filename2[100];

    printf("Enter the file you want to display(without .txt): \n");
    scanf("%s", filename);
    sprintf(filename2, "%s.txt", filename);
    /* opens the file in read mode */
    fp = fopen(filename2, "r");

    /* NULL if last operation was unsuccessful */
    if(fp == NULL)
    {
        printf("Unable to open file.\n");
        exit(1);
    }
    printf("File opened successfully. \n\n");
    while (ch != EOF)
    {
        /* Read single character from file */
        ch = fgetc(fp);
        /* Print character */
        putchar(ch);
    }
    fclose(fp);
    return 0;
}

You're attempting to print it before checking if it's `EOF`. — Fiddling Bits, Jan 03 '21 at 02:02
ch should be an int, not a char. Also: it doesn't seem to be initialised. — wildplasser, Jan 03 '21 at 02:03
Not exact duplicate but related: [c - Why is “while ( !feof (file) )” always wrong? - Stack Overflow](https://stackoverflow.com/questions/5431941/why-is-while-feof-file-always-wrong) — MikeCAT, Jan 03 '21 at 02:04
Every time some process writes `Unable to open file.\n` to stdout, a kitten dies. `perror(filename2);` — William Pursell, Jan 03 '21 at 13:30
Don't read the parameter from stdin, and *never* use `"%s"` in a scanf. It is as bad as `gets()`. Just do `char *filename = argv[1]; char *filename2 = argv[2]` — William Pursell, Jan 03 '21 at 13:33

score 1 · Accepted Answer · answered Jan 03 '21 at 02:03

You have to check if the reading is successful before trying to use what is "read".

Also fgetc() returns int, so the variable ch should be int, otherwise it will make it difficult to distinguish between one of valid characters with EOF.

    for (;;)
    {
        /* Read single character from file */
        ch = fgetc(fp);

        /* Check if something is actually read */
        if (ch == EOF) break;

        /* Print character */
        putchar(ch);
      }

score 0 · Answer 2 · edited Jan 03 '21 at 04:36

0

Just copy the file contents to another file, and kill the file . And try once again. Some time it happens because of the garbage value.

Otherwise just use this code once the file is read.

fflush(stdin);
fflush(stdout);

if that didn't work use these in some other appropriate places in the code. Sometime it happens because of the input and output buffer.

edited Jan 03 '21 at 04:36

Dharman

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answered Jan 03 '21 at 04:30

krishnaacharyaa

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Why is there an extra "?" displayed after executing C program(to read aand display a txt file)

2 Answers2