swapctl(2) swapctl(2)
NAME
swapctl - manage swap space
SYNOPSIS
#include <sys/stat.h>
#include <sys/swap.h>
int swapctl(int cmd, void *arg);
DESCRIPTION
swapctl adds, deletes, or returns information about swap resources.
cmd specifies one of the following options contained in <sys/swap.h>:
SC_ADD /* add a resource for swapping */
SC_LIST /* list the resources for swapping */
SC_REMOVE /* remove a resource for swapping */
SC_GETNSWP /* return number of swap resources */
When SC_ADD or SC_REMOVE is specified, arg is a pointer to a swapres
structure containing the following members:
char *sr_name; /* pathname of resource */
off_t sr_start;/* offset to start of swap area */
off_t sr_length;/* length of swap area */
sr_start and sr_length are specified in 512-byte blocks. When
SC_LIST is specified, arg is a pointer to a swaptable structure
containing the following members:
int swt_n; /* number of swapents following */
struct swapent swt_ent[];/* array of swt_n swapents */
A swapent structure contains the following members:
char *ste_path;/* name of the swap file */
off_t ste_start;/* starting block for swapping */
off_t ste_length;/* length of swap area */
long ste_pages;/* number of pages for swapping */
long ste_free; /* number of ste_pages free */
long ste_flags;/* ST_INDEL bit set if swap file */
/* is now being deleted */
SC_LIST causes swapctl to return at most swt_n entries. The return
value of swapctl is the number actually returned. The ST_INDEL bit
is turned on in ste_flags if the swap file is in the process of being
deleted. When SC_GETNSWP is specified, swapctl returns as its value
the number of swap resources in use. arg is ignored for this
operation. The SC_ADD and SC_REMOVE functions will fail if calling
process does not have appropriate privileges.
RETURN VALUE
Upon successful completion, the function swapctl returns a value of 0
for SC_ADD or SC_REMOVE, the number of struct swapent entries
actually returned for SC_LIST, or the number of swap resources in use
for SC_GETNSWP. Upon failure, the function swapctl returns a value
of -1 and sets errno to indicate an error.
ERRORS
Under the following conditions, the function swapctl fails and sets
errno to:
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swapctl(2) swapctl(2)
EEXIST Part of the range specified by sr_start and sr_length is
already being used for swapping on the specified resource
(SC_ADD).
EFAULT arg, sr_name, or ste_path points outside the allocated
address space.
EINVAL The specified function value is not valid, the path
specified is not a swap resource (SC_REMOVE), part of the
range specified by sr_start and sr_length lies outside
the resource specified (SC_ADD), or the specified swap
area is less than one page (SC_ADD).
EISDIR The path specified for SC_ADD is a directory.
ELOOP Too many symbolic links were encountered in translating
the pathname provided to SC_ADD or SC_REMOVE .
ENAMETOOLONG
The length of a component of the path specified for
SC_ADD or SC_REMOVE exceeds {NAME_MAX} characters or the
length of the path exceeds {PATH_MAX} characters and
{_POSIX_NO_TRUNC} is in effect.
ENOENT The pathname specified for SC_ADD or SC_REMOVE does not
exist.
ENOMEM An insufficient number of struct swapent structures were
provided to SC_LIST, or there were insufficient system
storage resources available during an SC_ADD or
SC_REMOVE, or the system would not have enough swap space
after an SC_REMOVE.
ENOSYS The pathname specified for SC_ADD or SC_REMOVE is not a
file or block special device.
ENOTDIR Pathname provided to SC_ADD or SC_REMOVE contained a
component in the path prefix that was not a directory.
EPERM The process does not have appropriate privileges.
EROFS The pathname specified for SC_ADD is a read-only file
system.
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