You can use either the quota or the repquota commands to check quota limits and disk usage. The quota command can be used to check individual user and group quotas and disk usage. Only the super-user may examine quotas and usage for other users, or for groups that they are not a member of. The repquota command can be used to get a summary of all quotas and disk usage for file systems with quotas enabled.
The following is some sample output from the quota -v command for a user that has quota limits on two file systems.
Disk quotas for user test (uid 1002): Filesystem blocks quota limit grace files quota limit grace /usr 65* 50 75 5days 7 50 60 /usr/var 0 50 75 0 50 60
On the /usr file system in the above example this user is currently 15 blocks over their soft limit of 50 blocks and has 5 days of their grace period left. Note the asterisk * which indicates that the user is currently over their quota limit.
Normally file systems that the user is not using any disk space on will not show up in the output from the quota command, even if they have a quota limit assigned for that file system. The -v option will display those file systems, such as the /usr/var file system in the above example.