swapctl(2) System Calls swapctl(2)NAMEswapctl - manage swap space
SYNOPSIS
#include <sys/stat.h>
#include <sys/swap.h>
int swapctl(int cmd, void *arg);
DESCRIPTION
The swapctl() function 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 */
The sr_start and sr_length members are specified in 512-byte blocks. A
swap resource can only be removed by specifying the same values for the
sr_start and sr_length members as were specified when it was added.
Swap resources need not be removed in the order in which they were
added.
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 */
The SC_LIST function 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 VALUES
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 Either arg, sr_name, or ste_path points to an
illegal address.
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 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 struc‐
tures 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 con‐
tained a component in the path prefix that was
not a directory.
EPERM The {PRIV_SYS_MOUNT} was not asserted in the
effective set of the calling process.
EROFS The pathname specified for SC_ADD is a read-
only file system.
Additionally, the swapctl() function will fail for 32-bit interfaces
if:
EOVERFLOW The amount of swap space configured on the
machine is too large to be represented by a
32-bit quantity.
EXAMPLES
Example 1: The usage of the SC_GETNSWP and SC_LIST commands.
The following example demonstrates the usage of the SC_GETNSWP and
SC_LIST commands.
#include <sys/stat.h>
#include <sys/swap.h>
#include <stdio.h>
#define MAXSTRSIZE 80
main(argc, argv)
int argc;
char *argv[];
{
swaptbl_t *s;
int i, n, num;
char *strtab; /* string table for path names */
again:
if ((num = swapctl(SC_GETNSWP, 0)) == -1) {
perror("swapctl: GETNSWP");
exit(1);
}
if (num == 0) {
fprintf(stderr, "No Swap Devices Configured\n");
exit(2);
}
/* allocate swaptable for num+1 entries */
if ((s = (swaptbl_t *)
malloc(num * sizeof(swapent_t) +
sizeof(struct swaptable))) ==
(void *) 0) {
fprintf(stderr, "Malloc Failed\n");
exit(3);
}
/* allocate num+1 string holders */
if ((strtab = (char *)
malloc((num + 1) * MAXSTRSIZE)) == (void *) 0) {
fprintf(stderr, "Malloc Failed\n");
exit(3);
}
/* initialize string pointers */
for (i = 0; i < (num + 1); i++) {
s->swt_ent[i].ste_path = strtab + (i * MAXSTRSIZE);
}
s->swt_n = num + 1;
if ((n = swapctl(SC_LIST, s)) < 0) {
perror("swapctl");
exit(1);
}
if (n > num) { /* more were added */
free(s);
free(strtab);
goto again;
}
for (i = 0; i < n; i++)
printf("%s %ld\n",
s->swt_ent[i].ste_path, s->swt_ent[i].ste_pages);
}
SEE ALSOprivileges(5)SunOS 5.10 25 Sep 1997 swapctl(2)
