all Python 3osfunction

os.dup2

os — file descriptors

Duplicate fd onto fd2 (closing fd2 first if needed) and return fd2.

Syntax

os.dup2(fd, fd2)

If fd2 was open it is closed silently — this is how standard streams are redirected at the OS level: dup2(fileno, 1) sends the output of child programs and C libraries to the file as well. Merely replacing sys.stdout does not achieve that. The new descriptor is inheritable by default (inheritable=True).

Examples

import os
fd = os.open(os.__file__, os.O_RDONLY)
fd2 = os.dup(fd)
print(os.dup2(fd, fd2) == fd2)   # → True
os.close(fd)
os.close(fd2)

See also

Common errors

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