fsck

Check the integrity of a filesystem or repair it. The filesystem should be unmounted at the time the command is run. It is a wrapper that calls fsck_hfs, fsck_apfs, fsck_msdos, fsck_exfat, and fsck_udf as needed. More information: https://keith.github.io/xcode-man-pages/fsck.8.html.

Check filesystem /dev/sdX, reporting any damaged blocks:

fsck {{/dev/sdX}}

Check filesystem /dev/sdX only if it is clean, reporting any damaged blocks and interactively letting the user choose to repair each one:

fsck -f {{/dev/sdX}}

Check filesystem /dev/sdX only if it is clean, reporting any damaged blocks and automatically repairing them:

fsck -fy {{/dev/sdX}}

Check filesystem /dev/sdX, reporting whether it has been cleanly unmounted:

fsck -q {{/dev/sdX}}