17.4.1 Popen3 and Popen4 Objects

17.4.1 Popen3 and Popen4 Objects

Instances of the Popen3 and Popen4 classes have the following methods:

poll( ): Returns -1 if child process hasn't completed yet, or its status code (see wait()) otherwise.

wait( ): Waits for and returns the status code of the child process. The status code encodes both the return code of the process and information about whether it exited using the exit() system call or died due to a signal. Functions to help interpret the status code are defined in the os module; see section 14.1.5 for the W*() family of functions.

The following attributes are also available:

fromchild: A file object that provides output from the child process. For Popen4 instances, this will provide both the standard output and standard error streams.

tochild: A file object that provides input to the child process.

childerr: A file object that provides error output from the child process, if capturestderr was true for the constructor, otherwise None. This will always be None for Popen4 instances.

pid: The process ID of the child process.

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