* Michael Kerrisk:
> SYNOPSIS
> int pidfd_open(pid_t pid, unsigned int flags);
Should this mention <sys/types.h> for pid_t?
> ERRORS
> EINVAL flags is not 0.
>
> EINVAL pid is not valid.
>
> ESRCH The process specified by pid does not exist.
Presumably, EMFILE and ENFILE are also possible errors, and so is
ENOMEM.
> A PID file descriptor can be monitored using poll(2), select(2),
> and epoll(7). When the process that it refers to terminates, the
> file descriptor indicates as readable. Note, however, that in the
> current implementation, nothing can be read from the file descrip‐
> tor.
“is indicated as readable” or “becomes readable”? Will reading block?
> The pidfd_open() system call is the preferred way of obtaining a
> PID file descriptor. The alternative is to obtain a file descrip‐
> tor by opening a /proc/[pid] directory. However, the latter tech‐
> nique is possible only if the proc(5) file system is mounted; fur‐
> thermore, the file descriptor obtained in this way is not pol‐
> lable.
One question is whether the glibc wrapper should fall back back to the
/proc subdirectory if it is not available. Probably not.
> static
> int pidfd_open(pid_t pid, unsigned int flags)
> {
> return syscall(__NR_pidfd_open, pid, flags);
> }
Please call this function something else (not pidfd_open), so that the
example continues to work if glibc provides the system call wrapper.
