1swapctl(2) System Calls swapctl(2)
2
6 swapctl - manage swap space
7
9 #include <sys/stat.h>
10 #include <sys/swap.h>
11 int swapctl(int cmd, void *arg);
13
16 The swapctl() function adds, deletes, or returns information about
17 swap resources. cmd specifies one of the following options contained in
18 <sys/swap.h>:
19 SC_ADD /* add a resource for swapping */
21 SC_LIST /* list the resources for swapping */
22 SC_REMOVE /* remove a resource for swapping */
23 SC_GETNSWP /* return number of swap resources */
24 When SC_ADD or SC_REMOVE is specified, arg is a pointer to a swapres
28 structure containing the following members:
29 char *sr_name; /* pathname of resource */
31 off_t sr_start; /* offset to start of swap area */
32 off_t sr_length; /* length of swap area */
33 The sr_start and sr_length members are specified in 512-byte blocks. A
37 swap resource can only be removed by specifying the same values for the
38 sr_start and sr_length members as were specified when it was added.
39 Swap resources need not be removed in the order in which they were
40 added.
41 When SC_LIST is specified, arg is a pointer to a swaptable structure
44 containing the following members:
45 int swt_n; /* number of swapents following */
47 struct swapent swt_ent[]; /* array of swt_n swapents */
48 A swapent structure contains the following members:
52 char *ste_path; /* name of the swap file */
54 off_t ste_start; /* starting block for swapping */
55 off_t ste_length; /* length of swap area */
56 long ste_pages; /* number of pages for swapping */
57 long ste_free; /* number of ste_pages free */
58 long ste_flags; /* ST_INDEL bit set if swap file */
59 /* is now being deleted */
60 The SC_LIST function causes swapctl() to return at most swt_n entries.
64 The return value of swapctl() is the number actually returned. The
65 ST_INDEL bit is turned on in ste_flags if the swap file is in the
66 process of being deleted.
67 When SC_GETNSWP is specified, swapctl() returns as its value the number
70 of swap resources in use. arg is ignored for this operation.
71 The SC_ADD and SC_REMOVE functions will fail if calling process does
74 not have appropriate privileges.
75
77 Upon successful completion, the function swapctl() returns a value of 0
78 for SC_ADD or SC_REMOVE, the number of struct swapent entries actually
79 returned for SC_LIST, or the number of swap resources in use for
80 SC_GETNSWP. Upon failure, the function swapctl() returns a value of −1
81 and sets errno to indicate an error.
82
84 Under the following conditions, the function swapctl() fails and sets
85 errno to:
86 EEXIST Part of the range specified by sr_start and sr_length
88 is already being used for swapping on the specified
89 resource (SC_ADD).
90 EFAULT Either arg, sr_name, or ste_path points to an illegal
93 address.
94 EINVAL The specified function value is not valid, the path
97 specified is not a swap resource (SC_REMOVE), part of
98 the range specified by sr_start and sr_length lies out‐
99 side the resource specified (SC_ADD), or the specified
100 swap area is less than one page (SC_ADD).
101 EISDIR The path specified for SC_ADD is a directory.
104 ELOOP Too many symbolic links were encountered in translating
107 the pathname provided to SC_ADD or SC_REMOVE.
108 ENAMETOOLONG The length of a component of the path specified for
111 SC_ADD or SC_REMOVE exceeds NAME_MAX characters or the
112 length of the path exceeds PATH_MAX characters and
113 _POSIX_NO_TRUNC is in effect.
114 ENOENT The pathname specified for SC_ADD or SC_REMOVE does not
117 exist.
118 ENOMEM An insufficient number of struct swapent structures
121 were provided to SC_LIST, or there were insufficient
122 system storage resources available during an SC_ADD or
123 SC_REMOVE, or the system would not have enough swap
124 space after an SC_REMOVE.
125 ENOSYS The pathname specified for SC_ADD or SC_REMOVE is not a
128 file or block special device.
129 ENOTDIR Pathname provided to SC_ADD or SC_REMOVE contained a
132 component in the path prefix that was not a directory.
133 EPERM The {PRIV_SYS_MOUNT} was not asserted in the effective
136 set of the calling process.
137 EROFS The pathname specified for SC_ADD is a read-only file
140 system.
141 Additionally, the swapctl() function will fail for 32-bit interfaces
145 if:
146 EOVERFLOW The amount of swap space configured on the machine is too
148 large to be represented by a 32-bit quantity.
149
152 Example 1 The usage of the SC_GETNSWP and SC_LIST commands.
153 The following example demonstrates the usage of the SC_GETNSWP and
156 SC_LIST commands.
157 #include <sys/stat.h>
160 #include <sys/swap.h>
161 #include <stdio.h>
162 #define MAXSTRSIZE 80
164 main(argc, argv)
166 int argc;
167 char *argv[];
168 {
169 swaptbl_t *s;
170 int i, n, num;
171 char *strtab; /* string table for path names */
172 again:
174 if ((num = swapctl(SC_GETNSWP, 0)) == -1) {
175 perror("swapctl: GETNSWP");
176 exit(1);
177 }
178 if (num == 0) {
179 fprintf(stderr, "No Swap Devices Configured\n");
180 exit(2);
181 }
182 /* allocate swaptable for num+1 entries */
183 if ((s = (swaptbl_t *)
184 malloc(num * sizeof(swapent_t) +
185 sizeof(struct swaptable))) ==
186 (void *) 0) {
187 fprintf(stderr, "Malloc Failed\n");
188 exit(3);
189 }
190 /* allocate num+1 string holders */
191 if ((strtab = (char *)
192 malloc((num + 1) * MAXSTRSIZE)) == (void *) 0) {
193 fprintf(stderr, "Malloc Failed\n");
194 exit(3);
195 }
196 /* initialize string pointers */
197 for (i = 0; i < (num + 1); i++) {
198 s->swt_ent[i].ste_path = strtab + (i * MAXSTRSIZE);
199 }
200 s->swt_n = num + 1;
202 if ((n = swapctl(SC_LIST, s)) < 0) {
203 perror("swapctl");
204 exit(1);
205 }
206 if (n > num) { /* more were added */
207 free(s);
208 free(strtab);
209 goto again;
210 }
211 for (i = 0; i < n; i++)
212 printf("%s %ld\n",
213 s->swt_ent[i].ste_path, s->swt_ent[i].ste_pages);
214 }
215
218 privileges(5)
219SunOS 5.11 25 Sep 1997 swapctl(2)