Ensure a TCP/IP interface is available
if_up [-alp] [-r retries] [-s seconds] interface...
- Wait until all specified interfaces are configured. The default is to wait until a single interface is configured.
- (el) Wait for the network link to be marked as being up. This causes if_up to wait until the physical network link is up. This option may not be supported by some drivers.
- Wait only until the specified interfaces are present. The default is to wait until the interfaces are both present and configured. This is useful if you intend to configure the interface manually, after it is present (e.g. using the ifconfig utility).
- -r retries
- The number of times to walk the interface list. The default is 5.
- -s seconds
- Wait this number of seconds before rewalking the interface list. The default is 1.
- The name of the interface to wait on (e.g. en0, en1, …).
You can use this convenience utility while booting to ensure a TCP/IP interface is available to those utilities that require one. It's primarily intended for use with the dhcp.client. When if_up is run in the foreground in a startup script, the script doesn't continue until the specified interfaces are marked as UP and have been assigned an IP address, or the utility has timed out.
- The if_up utility requires the libsocket.so shared library.
- The if_up utility is located in the /usr/sbin/ directory, which isn't included in the default PATH of non-root users. If you aren't root, specify the full path.
- An error occurred.