swaplabel.c - ubase - suckless linux base utils
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       swaplabel.c (1929B)
       ---
            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, 10))
           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_LENGTH)
           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] != '\0')
           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)strlen(label) + 1)
           74                         eprintf("writing label failed:");
           75         }
           76 
           77         fsync(fd);
           78         close(fd);
           79         return 0;
           80 }