posix-spawn
This repo contains Python bindings for the low-level Linux posix_spawn() and posix_spawnp()
functions via CFFI.
Those functions are similar to a combined fork()/exec() but they avoid the need to copy the
kernel's memory management metadata during the fork(), only to throw it away with the exec().
Since users of fork() typically need to manipulate file descriptors, in the child process,
between fork() and exec(), posix_spawn() provides a mechanism to queue up operations on
file descriptors to be executed in the child process before the child program is executed.
This is provided by the FileActions class. For example, to redirect stdout to the parent
via a pipe:
from posix_spawn import *
import os
# Create the pipe.
c2pread, c2pwrite = os.pipe()
# Tell posix_spawn to replace the child's stdout with the write end of the pipe.
file_actions = FileActions()
file_actions.add_dup2(c2pwrite, 1)
# Close the parent's end of the pipe in the child.
file_actions.add_close(c2pread)
# Execute the child process. posix_spawnp resolves the path.
pid = posix_spawnp("echo", ["echo", "Hello world!"], file_actions=file_actions)
# Close the child's end of the socket in the parent.
os.close(c2pwrite)
# Replace FD with a file object.
f = os.fdopen(c2pread, "r")
# And get the output.
f.read() # Returns "Hello world!\n"
# Clean up the child process.
os.waitpid(pid, 0) # Returns (pid, <returncode>)
