Copy program not working

skie_knite007 · 08-21-2005, 10:13 AM

Something is wrong with this program,,,I don't kno wat.............

When i run it,,,I'm getting a file of only 0 bytes.
Pls help out.

Code:

#include<stdio.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<unistd.h>
#include<fcntl.h>

char buffer[2048];



int main(int argc,char *argv[])
{
int fdnew,fdold;
if(argc!=3)
{
printf("\nNeed two arguments for the copy program.");
exit(0);
}
fdold=open(argv[1],O_RDONLY);
if(fdold<0)
{
printf("\nCanoot open the designated file.Check permissions.");
exit(0);
}
fdnew=creat(argv[2],0666);
if(fdnew<0)
{
printf("\nCannot create the designated file.There might not be enough disk space.");

}

int count;
while((count==read(fdold,buffer,sizeof(buffer)))>0)
{
write(fdnew,buffer,count);
}


exit(0);
}

Dave Kelly · 08-21-2005, 10:41 AM

The code is doing ONLY what you tell it to do.
Make a flow chart of what is suppose to happen.

keefaz · 08-21-2005, 10:44 AM

Also, you should close() your opened files at the end of the operation

zeropash · 08-28-2005, 04:53 AM

as keefaz told its a good practice to do the corresponding cleanup operation always.
btw are you sure you want == here?

Code:

while((count==read(fdold,buffer,sizeof(buffer)))>0)

though writing multiple statements in a single line looks cool try to avoid it or run into problems like these. Also while posting indend the stuff. make it little easier for the person trying to go trhough your posted code.

eddiebaby1023 · 08-28-2005, 02:13 PM

Quote:

Originally posted by zeropash
as keefaz told its a good practice to do the corresponding cleanup operation always.
btw are you sure you want == here?

Code:

while((count==read(fdold,buffer,sizeof(buffer)))>0)

though writing multiple statements in a single line looks cool try to avoid it or run into problems like these.

Well spotted zeropash, straight to the heart of the problem. count is undefined, so the likelihood of read() returning the same value to yield an expression value of true (that being >0) is less than your chance of winning the Lotto. An assignment would, of course, do the trick nicely.