Thread: mkstemp inside a loop

Hi folks,
i'm writting a piece of code, and i need to write data to temporary files created by mkstemp function.
The problem occurs at the second and later calls.
Here is the strace output of a sample.c :

sample.c

Code:

#include <stdio.h>
char tn[]="/tmp/TEST-XXXXXX";
int main(int argc, char *argv[]){
 int i,tmpfd;
        for(i=0;i<5;i++) {
                tmpfd=mkstemp(tn);
                write(tmpfd,"HI\n",3);
                close(tmpfd);
        }
        return 0;
}

The strace output:

Code:

open("/tmp/TEST-uvSflv", O_RDWR|O_CREAT|O_EXCL, 0600) = 3
write(3, "OI\n", 3)   = 3
close(3)                = 0
write(-1, "OI\n", 3) = -1 EBADF (Bad file descriptor)
close(-1)               = -1 EBADF (Bad file descriptor)
write(-1, "OI\n", 3)  = -1 EBADF (Bad file descriptor)
close(-1)                = -1 EBADF (Bad file descriptor)
write(-1, "OI\n", 3)   = -1 EBADF (Bad file descriptor)
close(-1)                 = -1 EBADF (Bad file descriptor)
write(-1, "OI\n", 3)    = -1 EBADF (Bad file descriptor)
close(-1)                 = -1 EBADF (Bad file descriptor)
exit_group(0)           = ?

So the mkstemp fail to open a new fd every new call inside a loop.
Well, according to the manpage the mkstemp function create and open the file, so we expect a new file (fd) every time right?

somebody know why this happen and how fix this ?
thanks a lot!

You need to reset your template string to have the 6 X's in it.

http://pubs.opengroup.org/onlinepubs...s/mkstemp.html

The mkstemp() function shall replace the contents of the string pointed to by template by a unique filename