not output after program was run?

Question

I am very confused to why my program isn't running well. I am connected to a server through my windows PC using PuTTY. It always works fine but something weird is going on I believe. Here's the code for identify.c :

#include <stdio.h>
#include <ctype.h>

int main()
{
    while(1)
    {
        char word[256];
        int i;
        int validity = 1;

        scanf("%s", word);

        for(i=0; word[i]!='\0'; i++)
        {
            if(i == 0)
            {
                /* First character should only be underscore or a letter */
                if(word[i]!= '_' && !isalpha(word[i]))
                {
                    validity = 0;
                    break;
                }

            }
            else
            {
                /* Rest can be Alpha-numerics or underscore */
                if(word[i]!= '_' && !isalnum(word[i]))
                {
                    validity = 0;
                    break;
                }
            }

        }

        if(validity)
            printf("valid\n");
        else
            printf("invalid\n");
    }

    return 0;
}

Here's the input file for testing if a name is a possible identifier name or not. identitytest.txt :

name

name2

2name

_name

__name

na_me

@name

na-me

I then upload both files to my server using FileZilla.

I then do the following command to make identify.c executable:

gcc identify.c -o identify

Executable has been created. Then I run the following command:

identify <identifytest.txt >output.txt

The created output.txt is then empty.

Any ideas why? I've been going crazy over this for the past 2 days not figuring out what is happening.

Step 1: Limit input length. Change to `scanf("%255", word);` 2) check result of `scanf()`, `if (1 != scanf("%255", word)) break;` — chux - Reinstate Monica, May 22 '15 at 20:13
You edited your question to remove ALL the code. Bad form. I restored it for you. — abelenky, May 22 '15 at 21:22

simon · Answer 1 · 2015-05-22T20:16:59.523

1

You have to break the infinite loop when std input closed:

if (scanf("%s", word) == EOF) break;

also you can flush standard output to force writing the results to the output file:

fflush(stdout);

edited May 22 '15 at 20:16

answered May 22 '15 at 20:06

simon

1,210
12
26

I changed it to !feof(stdin) but now it created an output file with millions of answers (true, false) – countryball May 22 '15 at 20:15

score 0 · Answer 2 · answered May 22 '15 at 20:32

0

Your program does not have an exit condition. I only added one line

if(i == 0)
    {
    if (word[i] == '!') return 0;       // <--- added this line
    ...

Then the command (similar to yours)

test <test.txt >output.txt

writes the expected results to output.txt after the line "!" is read.

answered May 22 '15 at 20:32

Weather Vane

33,872
7
36
56

I did this exact modification and it now still creates an output file with millions of results :/ – countryball May 22 '15 at 20:40
You changed the question.It said "The created output.txt is then empty.". Now you say "millions of results". Which is it? – Weather Vane May 22 '15 at 20:44
It had no output before, now after the edit it shown lots and lots of answers. – countryball May 22 '15 at 20:45
You changed the asked question to nothing, and I rolled it back. Otherwise it is meaningless. – Weather Vane May 22 '15 at 20:52

not output after program was run?

2 Answers2