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EAGAIN and EWOULDBLOCK

stackoverflow What does EAGAIN mean?

A

EAGAIN is often raised when performing non-blocking I/O. It means "there is no data available right now, try again later".

It might (or might not) be the same as EWOULDBLOCK, which means "your thread would have to block in order to do that".

errno(3)

Error numbers and names

All the error names specified by POSIX.1 must have distinct values, with the exception of EAGAIN and EWOULDBLOCK, which may be the same. On Linux, these two have the same value on all architectures.

List of error names

EAGAIN

Resource temporarily unavailable (may be the same value as EWOULDBLOCK) (POSIX.1-2001).