Updating a record in C

[JamesPowell]

Hi,

A simple problem, but I just can't get it to work...
I'm trying to read a record from a file, modify it and then write it back to file, updating the original record.

Can anyone tell me what I'm doing wrong.
I'm doing something like this.

void main (int argc, char *argv[])
{
char rec[3];

FILE *fp = fopen("a.dat", "r+");
int bytes = fread(rec, 1, sizeof(rec), fp);
rec[0] = 'V';
bytes = fwrite(rec, 1, sizeof(rec), fp);

fclose(fp);
}

Thanks

James

 

[carlg]

I think you need to rewind your file pointer back to the beginning of the file before you write.

fseek would be the function to use for this.

Carl

 

[maur3r]

Is it a binary file?

 

[JamesPowell]

No its not a binary file.
But, its fixed now anyway.
carlg was correct when he said to use the fseek() function.

Thanks anyway