quotactl - manipulate disk quota
int quotactl(int cmd, const char *special, int id, caddr_t addr);
The quota system defines for each user and/or group a soft limit and a
hard limit bounding the amount of disk space that can be used on a
given file system. The hard limit cannot be crossed. The soft limit
can be crossed, but warnings will ensue. Moreover, the user cannot be
above the soft limit for more than one week (by default) at a time:
after this week the soft limit counts as hard limit.
The quotactl() system call manipulates these quota. Its first argument
is of the form QCMD(subcmd,type) where type is either USRQUOTA or
GRPQUOTA (for user quota and group quota, respectively), and subcmd is
The second argument special is the block special device these quota
apply to. It must be mounted.
The third argument id is the user or group ID these quota apply to
The fourth argument addr is the address of a data structure, depending
on the command.
The subcmd is one of
Q_QUOTAON Enable quota. The addr argument is the pathname of the file
containing the quota for the file system.
Q_QUOTAOFF Disable quota.
Q_GETQUOTA Get limits and current usage of disk space. The addr
argument is a pointer to a dqblk structure (defined in
Q_SETQUOTA Set limits and current usage; addr is as before.
Q_SETQLIM Set limits; addr is as before.
Q_SETUSE Set usage.
Q_SYNC Sync disk copy of a file system’s quota.
Q_GETSTATS Get collected stats.
On success, quotactl() returns 0. On error, -1 is returned, and errno
is set appropriately.
EACCES The quota file is not an ordinary file.
EBUSY Q_QUOTAON was asked, but quotas were enabled already.
EFAULT Bad addr value.
EINVAL type is not a known quota type. Or, special could not be
EIO Cannot read or write the quota file.
EMFILE Too many open files: cannot open quota file.
ENODEV special cannot be found in the mount table.
ENOPKG The kernel was compiled without quota support.
ENOTBLK special is not a block special device.
EPERM The process was not root (for the file system), and Q_GETQUOTA
was asked for another id than that of the process itself, or
anything other than Q_GETSTATS or Q_SYNC was asked.
ESRCH Q_GETQUOTA or Q_SETQUOTA or Q_SETUSE or Q_SETQLIM was asked
for a file system that didn’t have quota enabled.
quota(1), getrlimit(2), setrlimit(2), ulimit(3), quotacheck(8),
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