fcntl_flags

⚙️ Manipulating File Descriptors with fcntl

For ultimate control over IO behavior, use Fcntl constants to tweak descriptor flags. For instance, setting O_SYNC forces writes to hit the disk, and O_NONBLOCK toggles non-blocking mode.

require 'fcntl'

fd = IO.sysopen('data.log', Fcntl::O_RDWR | Fcntl::O_CREAT)
io = IO.new(fd)

# Enable synchronous writes
flags = io.fcntl(Fcntl::F_GETFL, 0)
io.fcntl(Fcntl::F_SETFL, flags | Fcntl::O_SYNC)

i.write("Important log entry\n")
io.close

Adjusting these flags can help with real-time guarantees or integrating with event loops.