unix semantics fuck up

[Marc Espie]

$ cat goodfilename
coincoin

$ perl -pi -e 's/toto/tutu/' goodfilename
works

$ cp goodfilename /tmp
$ perl -pi -e 's/toto/tutu/' /tmp/goodfilename
Can't do inplace edit on goodfilename: File exists.
$ cat /tmp/goodfilename
cat: /tmp/goodfilename: No such file or directory.

ktrace shows a disturbing lack of Unix semantics:
 ....
 15350 perl     CALL  open(0x1850b9e863f0,0<O_RDONLY>)
 15350 perl     NAMI  "goodfilename"
 15350 perl     RET   open 3
 ...
 15350 perl     CALL  unlink(0x1850b9e86a00)
 15350 perl     NAMI  "goodfilename"
 15350 perl     RET   unlink 0
 15350 perl     CALL  
open(0x1850b9e868e0,0xa01<O_WRONLY|O_CREAT|O_EXCL>,0x180<S_IRUSR|S_IWUSR>)
 15350 perl     NAMI  "goodfilename"
 15350 perl     RET   open -1 errno 17 File exists


err...

simply put:

#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>

int 
main()
{
        if (open("fucked_up", O_RDWR|O_CREAT|O_TRUNC, 0666) == -1)
                perror("open");
        if (unlink("fucked_up") != 0)
                perror("unlink");
        if (open("fucked_up", O_WRONLY|O_CREAT|O_EXCL, 0666) == -1)
                perror("reopen");
        return 0;
}