pgrep: Better warning if pidfd_open not implemented
If procps is built on a Linux 5.3+ system then pidwait
is built with pidfd_open(). If that program is run on
a system < 5.3 then it gives an odd generic error.
If we get a ENOSYS from one pid, we will get it for all
the others so its better to explain what happens and terminate.
The man page is updated to note this issue.
This came up due to killall in psmisc using pidfd_send_signal
References:
https://bugs.debian.org/
1015228
Signed-off-by: Craig Small <csmall@dropbear.xyz>
projects / procps-ng / commit