closefds

closefds is a library that provides support for setting the FD_CLOEXEC flag on all open file descriptors after fork() and before exec() on UNIX-like systems.

Any file descriptors that aren't marked with this flag will stay open after exec() which can cause resources to leak and can lead to deadlocks. Ideally, whenever a file descriptor is created, it will be created with the FD_CLOEXEC flag already set. However, this may not be possible in some circumstances - such as when using an external library or a system call that does not support the FD_CLOEXEC flag, such as pipe().

The function close_fds_on_exec() will create a closure that can be passed as a pre_exec() function when spawning a child process via the Command interface and will set the FD_CLOEXEC flag as appropriate on open file descriptors.