Is there any command to find out how long a particular interface has been up on a cisco switch ?
There is no such command (that I’m aware of). The only way I can think of is looking at log entries on the device for an entry of when an interface changed its state to Up. This assumes that you have appropriate logging levels defined that will log such an event. That type of an event is generally at Informational and higher. I say generally because the logging level can be altered on a message-by-message basis on some devices. For example, a message may be classified as Informational by default but an admin may alter it to be reclassified as Warning.