CODEWITHSUNDEEP
c
user1736495
user1736495

Reputation: 51

fopen doesn't open

I am using Code::Blocks and have set the command-line arugments via the IDE. I have also opened the executable with the proper argument and I can't manage to get a non-NULL on fopen() return. I've tried hard-coding the filename also with no success. The platform is Windows XP SP3.

The first is the one that fails, when i hardcoded it i used double backlash. Also i never knew if the second works because i never managed to start the process by opening the first one.

Obviously i put the text file in the same directory that the executable and rebuilt the executable many times, but it still doesn't work.

EDIT: I added the perror("fopen"); line in the if(finput==NULL) block. This is the output.

http://prntscr.com/h71pa

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

#define first_part_url "[url=http://magiccards.info/query?q="
#define second_part_url "&v=card&s=cname]"
#define end_bracket "[/url]\n"
#define output_file_prefix "output_"

char* get_card(FILE* finput);

int main(int n, char* arguments[])
{
FILE* finput;
FILE* foutput;
short int counter;
char* output_filename;
char* finalstring;


for(counter=1; counter<n; counter++)
{
    finput=fopen(arguments[counter], "r");

    if (finput==NULL)
    {
        printf("Unable to open ");
        puts(arguments[counter]);
                    perror("fopen");
        break;
    }

    strcpy(output_filename, output_file_prefix);
    strcat(output_filename, arguments[counter]);

    if((foutput=fopen(output_filename, "w"))==NULL)
    {
        printf("There was an error while trying to open ");
        puts(arguments[counter]);
        printf(" .\n");
        break;
    }

    while(!feof(finput))
    {
    finalstring=get_card(finput);
    fputs(finalstring, foutput);
    while(((fgetc(finput))!='\n')||feof(finput));
    }

    printf("Autocarding ");
    puts(arguments[counter]);
    printf(" was a success.\n");
    fclose(foutput);
}

if(finput!=NULL)
{
fclose(finput);
free(finalstring);
}
return 0;
}

char* get_card(FILE* finput)
{
char* currentcard;
char* finalstring;

currentcard=(char*)malloc(sizeof(char)*150);
fgets(currentcard, 150, finput);

/* Allocates the exact amount of space needed for the final string*/
finalstring=(char*)malloc(sizeof(char)*(strlen(first_part_url)+strlen(second_part_url)+strlen(end_bracket)+strlen(currentcard)));

/* Get all the final forum link together*/
strcat(finalstring, first_part_url);
strcat(finalstring, currentcard);
strcat(finalstring, second_part_url);
strcat(finalstring, end_bracket);

free(currentcard);

return finalstring;
}

Upvotes: 2

Views: 2942

Answers (3)

caf
caf

Reputation: 239341

The error you are getting, "No such file or directory" indicates that the file name you're trying to open doesn't exist.

In this case, it's probably because the program's current working directory is not the same as the directory containing the executable file.

Upvotes: 2

user922475
user922475

Reputation:

Try changing

for(counter=1; counter<n; ++n)
{

to 

for(counter=1; counter<n; ++counter)

It appears the code loops infinitely, therefore it would exhaust the possible elements in your argument array causing a NULL pointer to be returned.

Upvotes: 0

Alexey Frunze
Alexey Frunze

Reputation: 62106

This

finput=fopen(arguments[counter], "r");

Will only fail if you do not supply correct filenames (e.g. if there are non-ASCII characters in the names or the names do not include the correct path, fopen() opens files in the current directory if no path is specified in the file name).

This

output_filename=(char*)malloc(sizeof(arguments[counter]));

most likely does not allocate enough space for a name because arguments[counter] is a pointer, and sizeof() of a pointer is not the same as strlen(that_same_pointer) + 1.

This

output_filename=output_file_prefix;

loses the just allocated memory because you are reassigning the pointer output_filename to point to some other place, output_file_prefix ("output_").

After the above this

strcat(output_filename, arguments[counter]);

is likely going to crash your program because this is going to attempt to overwrite a string literal ("output_"), doing which causes undefined behavior per the C standard.

You have to allocate enough cumulative space for the strings that you want to concatenate and you have to concatenate them in the allocated space.

To save you even more trouble, here's another problem:

finput=fopen(arguments[counter], "r");
...
while(!feof(finput))

feof() only works after at least one read from a file. This has been asked ans answered multiple times.

Upvotes: 0

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