How can I tell the size of a text file?

Thanks for all the replies. To clarify, what I want to do is read the number of bytes in a simple text file i created with fopen. Contents of the file are:

Code:

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Name        Number
==================

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So that is 31 bytes of data. I want something else to execute if there are more than 31 bytes of data. How should I do this? The stuff I saw on stat() didn't clarify much, and I think we are supposed to be using more basic methods (its for a class).

Thanks!

Quote:

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Originally Posted by sharrakor

Thanks for all the replies. To clarify, what I want to do is read the number of bytes in a simple text file i created with fopen. Contents of the file are:

Code:

---

Name        Number
==================

---

So that is 31 bytes of data. I want something else to execute if there are more than 31 bytes of data. How should I do this? The stuff I saw on stat() didn't clarify much, and I think we are supposed to be using more basic methods (its for a class).

Thanks!

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My suggestion would be to read in the header, and then try to read more data. Either the read will succeed, in which case hooray, or the read will fail, in which case the file only had the two lines in it.

Ok, so if it is acceptable to you that it MAY NOT WORK ON ALL PLATFORMS, try

Code:

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file = fopen(...);
fseek(file, 0, SEEK_END)
length = ftell(file);
if (length != 31)
  ...
else
  ...

---

--
Mats

Quote:

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Originally Posted by tabstop

My suggestion would be to read in the header, and then try to read more data. Either the read will succeed, in which case hooray, or the read will fail, in which case the file only had the two lines in it.

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That is a good suggestion.

--
Mats

Quote:

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Originally Posted by tabstop

My suggestion would be to read in the header, and then try to read more data. Either the read will succeed, in which case hooray, or the read will fail, in which case the file only had the two lines in it.

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Out of curiosity, what functions would I need to use to do that? By read in you mean what I guess is a better question.

And thanks matsp. I'm trying to get that to work for me now.

Quote:

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Originally Posted by sharrakor

How should I do this? The stuff I saw on stat() didn't clarify much, and I think we are supposed to be using more basic methods (its for a class).

Thanks!

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Is it a class in C? You could do this in assembly if you want "the basic method". stat() works perfectly and gives you the exact size that you will see in a directory listing, which is to say the exact number of bytes occupied on the device.

Code:

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#include<stdio.h>
#include<sys/stat.h>

int filelen (char *file) {
        struct stat info;
        if (stat(file,&info)<0) return -1;
        else return (int)info.st_size;
}


int main(int argc, char *argv[]) {
        int self=filelen(argv[0]);
        printf("My name is %s and I am %d bytes long.\n",argv[0],self);
        return 0;
}

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In this case a binary file (the executable itself), but a text file is the same. Counting characters is not the same as counting bytes, as has been discussed, altho the count is usually the same. I doubt your prof is really going to expect you to use a character counting method that compensates for all the possible discrepancies, such as multibyte characters, etc. (unless this is a course about you doing independent internet research).

Quote:

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Originally Posted by sharrakor

Out of curiosity, what functions would I need to use to do that? By read in you mean what I guess is a better question.

And thanks matsp. I'm trying to get that to work for me now.

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fscanf? fgets?

stat(), however, isn't available in Windows/DOS - there is _stat() which does the same thing.

--
Mats

Quote:

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Originally Posted by matsp

stat(), however, isn't available in Windows/DOS - there is _stat() which does the same thing.

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Nuff said!

Alright, thanks guys, I got it working. Yes it is a class on C, so you're right. But our prof is supposed to have taught us all this, I just probably didn't get it.

By the way, MK27, I saw you used argv and argc. Is there any place you could point me to that would be a good place to learn those? Once I've got those in my code, I'm done.

Quote:

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Originally Posted by sharrakor

Alright, thanks guys, I got it working. Yes it is a class on C, so you're right. But our prof is supposed to have taught us all this, I just probably didn't get it.

By the way, MK27, I saw you used argv and argc. Is there any place you could point me to that would be a good place to learn those? Once I've got those in my code, I'm done.

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Hmmm...I probably got it from some "C in 24 hours" book. You include them as the arguments to main. You could call them anything, but they are the only possible arguments to main() anyway: the first is an int representing the length of the second argument (argv) which is an array of char *pointers. argc is always at least 1, because the first pointer in the array contains the name of the program as it was compiled (eg, "myprog.exe"). The rest of the array will be arguments used on the command line, so what argv actually is is the command-line invocation itself:

Quote:

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myprog -x somefile.txt

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argc=3
argv[0]=myprog
argv[1]=-x
argv[2]=somefile.txt

Update: I've got this code:

Code:

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


int main(int argc, char **argv)
{

char *filename;
if (argc == 1)
{
printf ("The name of the file is missing!\n");
exit (1);
}
else
filename = argv[1];

printf("filename is: %s\n",filename);

FILE *fp;
fp=fopen(filename,"w");
fscanf(fp,"this text should be in a new file in the same folder as the executable");
fclose(fp);
        system("PAUSE");
                return 0;
}

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And it outputs TESTING.txt for filename (when run in cmd as: c:\delete.exe TESTING.txt ), but it doesn't actually create the file. Anyone know why?

Quote:

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Originally Posted by sharrakor

Update: I've got this code:

Code:

---

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


int main(int argc, char **argv)
{

char *filename;
if (argc == 1)
{
printf ("The name of the file is missing!\n");
exit (1);
}
else
filename = argv[1];

printf("filename is: %s\n",filename);

FILE *fp;
fp=fopen(filename,"w");
fscanf(fp,"this text should be in a new file in the same folder as the executable");
fclose(fp);
        system("PAUSE");
                return 0;
}

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And it outputs TESTING.txt for filename (when run in cmd as: c:\delete.exe TESTING.txt ), but it doesn't actually create the file. Anyone know why?

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Are you saying that the file is not existing, or that it exists, but is empty?

Do you actually think that fscanf() will work on an output file? And that it will produce something in the file?

--
Mats