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 con-
tained 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:

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 .

ENAMETOOLONGThe length of a component of the path  specified
            for SC_ADD or SC_REMOVE exceeds {NAME_MAX} char-
            acters  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.