[3.7] bpo-33550: Warn not to set SIGPIPE to SIG_DFL (GH-6773) by miss-islington · Pull Request #8798 · python/cpython
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@@ -485,3 +485,37 @@ be sent, and the handler raises an exception. ::
signal.alarm(0) # Disable the alarm
Note on SIGPIPE ---------------
Piping output of your program to tools like :manpage:`head(1)` will cause a :const:`SIGPIPE` signal to be sent to your process when the receiver of its standard output closes early. This results in an exception like :code:`BrokenPipeError: [Errno 32] Broken pipe`. To handle this case, wrap your entry point to catch this exception as follows::
import os import sys
def main(): try: # simulate large output (your code replaces this loop) for x in range(10000): print("y") # flush output here to force SIGPIPE to be triggered # while inside this try block. sys.stdout.flush() except BrokenPipeError: # Python flushes standard streams on exit; redirect remaining output # to devnull to avoid another BrokenPipeError at shutdown devnull = os.open(os.devnull, os.O_WRONLY) os.dup2(devnull, sys.stdout.fileno()) sys.exit(1) # Python exits with error code 1 on EPIPE
if __name__ == '__main__': main()
Do not set :const:`SIGPIPE`'s disposition to :const:`SIG_DFL` in order to avoid :exc:`BrokenPipeError`. Doing that would cause your program to exit unexpectedly also whenever any socket connection is interrupted while your program is still writing to it.
signal.alarm(0) # Disable the alarm
Note on SIGPIPE ---------------
Piping output of your program to tools like :manpage:`head(1)` will cause a :const:`SIGPIPE` signal to be sent to your process when the receiver of its standard output closes early. This results in an exception like :code:`BrokenPipeError: [Errno 32] Broken pipe`. To handle this case, wrap your entry point to catch this exception as follows::
import os import sys
def main(): try: # simulate large output (your code replaces this loop) for x in range(10000): print("y") # flush output here to force SIGPIPE to be triggered # while inside this try block. sys.stdout.flush() except BrokenPipeError: # Python flushes standard streams on exit; redirect remaining output # to devnull to avoid another BrokenPipeError at shutdown devnull = os.open(os.devnull, os.O_WRONLY) os.dup2(devnull, sys.stdout.fileno()) sys.exit(1) # Python exits with error code 1 on EPIPE
if __name__ == '__main__': main()
Do not set :const:`SIGPIPE`'s disposition to :const:`SIG_DFL` in order to avoid :exc:`BrokenPipeError`. Doing that would cause your program to exit unexpectedly also whenever any socket connection is interrupted while your program is still writing to it.