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QUOTACTL(2) System Calls Manual QUOTACTL(2)

quotactl — manipulate filesystem quotas

#include <sys/types.h> /* types needed by quota.h */
#include <sys/quota.h> /* for disk quotas */

int
quotactl(const char *path, int cmd, int id, char *addr);

The () call enables, disables and manipulates filesystem quotas. A quota control command given by cmd operates on the given filename path for the given user id. The address of an optional command specific data structure, addr, may be given; its interpretation is discussed below with each command.

A command is composed of a primary command (see below) and a command type used to interpret the id. Types are supported for interpretation of user identifiers and group identifiers. The specific commands are:

Enable disk quotas for the filesystem specified by path. The command type specifies the type of the quotas being enabled. The addr argument specifies a file from which to take the quotas. The quota file must exist; it is normally created with the quotacheck(8) program. The id argument is unused. Only the super-user may turn quotas on.
Disable disk quotas for the filesystem specified by path. The command type specifies the type of the quotas being disabled. The addr and id arguments are unused. Only the super-user may turn quotas off.
Get disk quota limits and current usage for the user or group (as determined by the command type) with identifier id. Addr is a pointer to a struct dqblk structure.
Set disk quota limits for the user or group (as determined by the command type) with identifier id. Addr is a pointer to a struct dqblk structure. The usage fields of the dqblk structure are ignored. This call is restricted to the super-user.
Set disk usage limits for the user or group (as determined by the command type) with identifier id. Addr is a pointer to a struct dqblk structure. Only the usage fields are used. This call is restricted to the super-user.
Update the on-disk copy of quota usages. The command type specifies which type of quotas are to be updated. The id and addr parameters are ignored.
Get the enable status for the filesystem specified by path. The command type specifies the type of the quotas whose status is being queried. Addr is a pointer to an integer. Upon return, this integer will hold a zero value if quotas for the given type are not enabled and a non-zero value if quotas for the given type are enabled. The id parameter is ignored.

A successful call returns 0, otherwise the value -1 is returned and the global variable errno indicates the reason for the failure.

A quotactl() call will fail if:

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The kernel has not been compiled with the QUOTA option.
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The quota table cannot be expanded.
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Cmd or the command type is invalid.
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In Q_QUOTAON, the quota file is not a plain file.
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Search permission is denied for a component of a path prefix.
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A component of a path prefix was not a directory.
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A component of a pathname exceeded {NAME_MAX} characters, or an entire path name exceeded {PATH_MAX} characters.
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A filename does not exist.
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Too many symbolic links were encountered in translating a pathname.
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In Q_QUOTAON, the quota file resides on a read-only filesystem.
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An I/O error occurred while reading from or writing to a file containing quotas.
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An invalid addr was supplied; the associated structure could not be copied in or out of the kernel.
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Path points outside the process's allocated address space.
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The call was privileged and the caller was not the super-user.

quota(1), fstab(5), edquota(8), quotacheck(8), quotaon(8), repquota(8)

There should be some way to integrate this call with the resource limit interface provided by setrlimit(2) and getrlimit(2).

The quotactl() function call appeared in 4.3BSD-Reno.

June 4, 1993 macOS