Hi

I am new to C prog..

I just want to know what is the problem with the following code.

#define BUFSIZE 1024
int main(void)
{
char *s;
FILE *fp;
s = malloc (BUFSIZE);

fp = fopen("~/Documents/newtxt.txt", "rb");
fgets( s, BUFSIZE, fp);
printf("%s", s);
return 0;
}

I have a text file in ~/Documents names newtxt with a line of text in it. I just want to read it and print it on screen. It compiles OK but when i execute it gives "SEGEMENTATION FAULT: CORE DUMPED"

I also tried fgets(s,BUFSIZE-1,fp) above.. same result.

Your help is appreciated.
Thanks.
Ash

You can’t pass the character ‘~’ as the home directory in your system calls. This only works if you have some sort of shell interpretation to handle your environment variables. You might have found this out if you bothered to check the return value of fopen().

Check if (!fp).
I'd bet that the ~ is the problem. Specify the full path and it should work.

Or use getenv("HOME").

Also, you should not assume char is one byte. Your malloc line should read:
And you should check that malloc worked too (check that s != NULL).

This is wrong. The C standard guarantees that
always evaluates to 1 (see §6.5.3.4.3). What one should not assume is that the number of bits in a char is 8.

I didn't know that was in the standard. In that case you probably can assume it will be a byte.

If you're ultra-paranoid you might still want to check it since char could be set to something else using a macro, although I expect that would break lots of other stuff before you have to worry about it in your own code.

I would do it like this (formatting is last unfortunately after posting the message):

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

#define BUFSIZE 1024
int main(void)
{
char *s;
FILE *fp;
char filename[64];

s = malloc (BUFSIZE);
if (!s) {
printf ("malloc error\n");
return -1L;
}
sprintf (filename, "%s/Documents/newtxt.txt", getenv("HOME"));

fp = fopen (filename, "rb");
if (!fp) {
printf ("fopen error\n");
return -2L;
}
fgets (s, BUFSIZE, fp);
printf ("%s", s);
fclose (fp);
return 0L;
}


Hope this helps,
Regards,
SIMP

Linux Archive

You could edit your post and put CODE tags around it?

Thanks people. Problem solved. It was the '~'.