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swaplabel.c - ubase - suckless linux base utils
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swaplabel.c (1929B)
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1 /* See LICENSE file for copyright and license details. */
2 #include <sys/types.h>
3
4 #include <fcntl.h>
5 #include <stdio.h>
6 #include <stdlib.h>
7 #include <string.h>
8 #include <unistd.h>
9
10 #include "util.h"
11
12 #define SWAP_MAGIC1 "SWAPSPACE2"
13 #define SWAP_MAGIC2 "SWAP-SPACE"
14 #define SWAP_MAGIC_LENGTH (10)
15 #define SWAP_MAGIC_OFFSET (sysconf(_SC_PAGESIZE) - SWAP_MAGIC_LENGTH)
16 #define SWAP_LABEL_LENGTH (16)
17 #define SWAP_LABEL_OFFSET (1024 + 4 + 4 + 4 + 16)
18
19 static void
20 usage(void)
21 {
22 eprintf("usage: %s [-L label] device\n", argv0);
23 }
24
25 int
26 main(int argc, char *argv[])
27 {
28 int setlabel = 0;
29 int fd;
30 char magic[SWAP_MAGIC_LENGTH];
31 char *label;
32 char *device;
33 int i;
34
35 ARGBEGIN {
36 case 'L':
37 setlabel = 1;
38 label = EARGF(usage());
39 break;
40 default:
41 usage();
42 } ARGEND;
43
44 if (argc < 1)
45 usage();
46 device = argv[0];
47
48 fd = open(device, O_RDWR);
49 if (fd < 0)
50 eprintf("open %s:", device);
51
52 if (lseek(fd, SWAP_MAGIC_OFFSET, SEEK_SET) != SWAP_MAGIC_OFFSET)
53 eprintf("failed seeking to magic position:");
54 if (read(fd, magic, SWAP_MAGIC_LENGTH) != SWAP_MAGIC_LENGTH)
55 eprintf("reading magic failed:");
56 if (memcmp(magic, SWAP_MAGIC1, 10) && memcmp(magic, SWAP_MAGIC2,…
57 eprintf("%s: is not a swap partition\n", device);
58 if (lseek(fd, SWAP_LABEL_OFFSET, SEEK_SET) != SWAP_LABEL_OFFSET)
59 eprintf("failed seeking to label position:");
60
61 if (!setlabel) {
62 label = emalloc(SWAP_LABEL_LENGTH);
63 if (read(fd, label, SWAP_LABEL_LENGTH) != SWAP_LABEL_LEN…
64 eprintf("reading label failed:");
65 for (i = 0; i < SWAP_LABEL_LENGTH && label[i] != '\0'; i…
66 if (i == (SWAP_LABEL_LENGTH - 1) && label[i] != …
67 eprintf("invalid label\n");
68 printf("label: %s\n", label);
69 free(label);
70 } else {
71 if (strlen(label) + 1 > SWAP_LABEL_LENGTH)
72 eprintf("label too long\n");
73 if (write(fd, label, strlen(label) + 1) != (ssize_t)strl…
74 eprintf("writing label failed:");
75 }
76
77 fsync(fd);
78 close(fd);
79 return 0;
80 }
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