Not every Linux system has /dev/fd

[cmorve-te]

I have found a couple of embedded Linux devices old enough to not have close_range, and that happen to lack the /dev/fd -> /proc/self/fd symlink (AFAICT it's not required by POSIX either). They do have /proc/self/fd, though.

So it would be nice if Boost.Process would try also in /proc/self/fd if /dev/fd fails:

process/src/posix/close_handles.cpp

Line 181 in 1bfe21b

std::unique_ptr<DIR, void(*)(DIR*)> dir{::opendir("/dev/fd"), +[](DIR* p){::closedir(p);}};

[klemens-morgenstern]

Is /dev/fd only ever a syslink to /proc/self/fd ? I.e. could I just use the latterin all case?

[cmorve-te]

/proc/self/fd is always available in Linux (as long as /proc is mounted). And yes, /dev/fd would be just a symlink there.

But outside Linux /dev/fd has its own history. My understanding is that the concept originated in BSD, where it's its own directory (from a quick look I just found https://man.bsd.lv/4.4BSD-Lite2/mount_fdesc.8). Without any authoritative reference, my understanding is that it's the same in macOS and Solaris.

So I guess the best solution is to use /proc/self/fd #elif defined(__linux__) (and close_range is not available), and keep /dev/fd for others.