Linux – Check if a path exceeds maximum for Unix domain socket

linuxmac-osxsocketssh

Operating systems limit the length of a path of a Unix domain socket. How can I check whether a particular path is within that limit?

Or, to put it another way, how can I check the maximum permitted length of a path of a Unix domain socket, on a Linux or Mac OS X system?

My use case here is for SSH multiplexing: if the ControlPath is too long, then SSH multiplexing won't work since it creates a unix domain sockets. I want to be able to check for a valid control path without having to actually start an ssh session and look for the error message.

Best Answer

how can I check the maximum permitted length of a path of a Unix domain socket, on a Linux

On Linux, this length is usually defined as 108.

It is defined by the UNIX_PATH_MAX variable in the /usr/include/linux/un.h header file :

cat /usr/include/linux/un.h | grep "define UNIX_PATH_MAX"

#define UNIX_PATH_MAX   108

You could find further info here :

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