samefilesystem

samefilesystem is a command-line utility designed to determine if two specified paths reside on the same underlying filesystem. It achieves this by examining the device identifiers associated with each path. When you provide two paths to samefilesystem, it retrieves the device ID for each path and compares them. If the device IDs are identical, it indicates that both paths are part of the same mounted filesystem. Conversely, if the device IDs differ, the paths are located on separate filesystems, which could be due to being on different partitions, disks, or even network mounts.

The primary use case for samefilesystem is in scripting and automation. For instance, when performing file operations that might involve copying or moving data, it's often more efficient to use a hard link or rename operation if the source and destination are on the same filesystem. If they are on different filesystems, a standard copy operation is necessary. samefilesystem helps scripts make these decisions automatically, optimizing performance and avoiding unnecessary data transfers. It can also be useful for diagnosing issues related to file permissions or accessibility, as understanding filesystem boundaries is crucial in such scenarios. The utility typically returns an exit code of 0 if the filesystems are the same and a non-zero exit code if they are different, making it easy to integrate into conditional logic.