Output of C programs | Set 40 (File handling)

Prerequisite : File handling
1. What is the output of this program by manipulating the text file?

#include <stdio.h>
int main()
{
    if (remove("myfile.txt") != 0)
        perror("Error");
    else
        puts("Success");
    return 0;
}

Options:
a) Error
b) Success
c) Runtime Error
d) Can’t say

Answer : d

Explanation : If myfile.txt exists, then it will delete the file. Else it will print an error message.

2. What is the output of this program?

#include <stdio.h>
int main()
{
    FILE* p;
    int c;
    int n = 0;
    p = fopen("myfile.txt", "r");
    if (p == NULL)
        perror("Error opening file");
    else {
        do {
            c = getc(p);
            if (c == '$')
                n++;
        } while (c != EOF);
        fclose(p);
        printf("%d\n", n);
    }
    return 0;
}

Options:
a) Count of ‘$’ symbol
b) Error opening file
c) Any of the mentioned
d) None of the mentioned

Answer : c

Explanation : Any one is possible – Either the file doesn’t exist or If exist, it will print the total number of ‘$’ character.
3. What is the output of this program in the text file?

#include <stdio.h>
int main()
{
    FILE* pFile;
    char c;
    pFile = fopen("sample.txt", "wt");
    for (c = 'A'; c <= 'E'; c++) {
        putc(c, pFile);
    }
    fclose(pFile);
    return 0;
}

Options:
a) ABCD
b) ABC
c) ABCDE
d) None of the mentioned

Answer : c

Explanation : In this program, We are printing from A to E by using the putc function.
Output:

$ g++ out2.cpp
$ a.out
ABCDE

4. What is the name of the myfile2 file after executing this program?

#include <stdio.h>
int main()
{
    int result;
    char oldname[] = "myfile2.txt";
    char newname[] = "newname.txt";
    result = rename(oldname, newname);
    if (result == 0)
        puts("success");
    else
        perror("Error");
    return 0;
}

Options:
a) name
b) new
c) newname
d) None of the mentioned

Answer : c 

Explanation : In this program, We are renaming the myfile2 to newname by using the function rename.
Output:

myfile2.txt is renamed to newname.txt 

5. How many number of characters are available in newname.txt?

#include <stdio.h>
int main()
{
    FILE* p;
    int n = 0;
    p = fopen("newname.txt", "rb");
    if (p == NULL)
        perror("Error opening file");
    else {
        while (fgetc(p) != EOF) {
            ++n;
        }
        if (feof(p)) {
            printf("%d\n", n);
        } else
            puts("End-of-File was not reached.");
        fclose(p);
    }
    return 0;
}

Options:
a) 10
b) 15
c) Depends on the text file
d) None of the mentioned

Answer : c

Explanation : In this program, We are reading the number of characters in the program by using the function feof.
Output:

$ g++ out4.cpp
$ a.out
162

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