commands/at/at.c

   1 /* at - run a command at a specified time       Author: Jan Looyen */
   2
   3 #include <sys/types.h>
   4 #include <time.h>
   5 #include <fcntl.h>
   6 #include <unistd.h>
   7 #include <stdlib.h>
   8 #include <string.h>
   9 #include <sys/stat.h>
  10 #include <stdio.h>
  11 #include <limits.h>
  12 #include <signal.h>
  13 #include <errno.h>
  14
  15 #define STARTDAY        0       /* see ctime(3)  */
  16 #define LEAPDAY         (STARTDAY+59)
  17 #define MAXDAYNR        (STARTDAY+365)
  18 #define NODAY           (-2)
  19 char CRONPID[]  =       "/usr/run/cron.pid";
  20
  21 int main(int argc, char **argv, char **envp);
  22 int getltim(char *t);
  23 int getlday(char *m, char *d);
  24 int digitstring(char *s);
  25
  26 int main(argc, argv, envp)
  27 int argc;
  28 char **argv, **envp;
  29 {
  30   int i, c, mask, ltim, year, lday = NODAY;
  31   char buf[64], job[30], pastjob[35], *dp, *sp;
  32   struct tm *p;
  33   long clk;
  34   FILE *fp;
  35   char pwd[PATH_MAX+1];
  36
  37 /*-------------------------------------------------------------------------*
  38  *      check arguments & pipe to "pwd"                                    *
  39  *-------------------------------------------------------------------------*/
  40   if (argc < 2 || argc > 5) {
  41         fprintf(stderr, "Usage: %s time [month day] [file]\n", argv[0]);
  42         exit(1);
  43   }
  44   if ((ltim = getltim(argv[1])) == -1) {
  45         fprintf(stderr, "%s: wrong time specification\n", argv[0]);
  46         exit(1);
  47   }
  48   if ((argc == 4 || argc == 5) && (lday = getlday(argv[2], argv[3])) == -1) {
  49         fprintf(stderr, "%s: wrong date specification\n", argv[0]);
  50         exit(1);
  51   }
  52   if ((argc == 3 || argc == 5) && open(argv[argc - 1], O_RDONLY) == -1) {
  53         fprintf(stderr, "%s: cannot find: %s\n", argv[0], argv[argc - 1]);
  54         exit(1);
  55   }
  56   if (getcwd(pwd, sizeof(pwd)) == NULL) {
  57         fprintf(stderr, "%s: cannot determine current directory: %s\n",
  58                 argv[0], strerror(errno));
  59         exit(1);
  60   }
  61
  62 /*-------------------------------------------------------------------------*
  63  *      determine execution time and create 'at' job file                  *
  64  *-------------------------------------------------------------------------*/
  65   time(&clk);
  66   p = localtime(&clk);
  67   year = p->tm_year;
  68   if (lday == NODAY) {          /* no [month day] given */
  69         lday = p->tm_yday;
  70         if (ltim <= (p->tm_hour * 100 + p->tm_min)) {
  71                 lday++;
  72                 if ((lday == MAXDAYNR && (year % 4)) || lday == MAXDAYNR + 1) {
  73                         lday = STARTDAY;
  74                         year++;
  75                 }
  76         }
  77   } else
  78         switch (year % 4) {
  79             case 0:
  80                 if (lday < p->tm_yday ||
  81                     (lday == p->tm_yday &&
  82                     ltim <= (p->tm_hour * 100 + p->tm_min))) {
  83                         year++;
  84                         if (lday > LEAPDAY) lday--;
  85                 }
  86                 break;
  87             case 1:
  88             case 2:
  89                 if (lday > LEAPDAY) lday--;
  90                 if (lday < p->tm_yday ||
  91                     (lday == p->tm_yday &&
  92                      ltim <= (p->tm_hour * 100 + p->tm_min)))
  93                         year++;
  94                 break;
  95             case 3:
  96                 if (lday < ((lday > LEAPDAY) ? p->tm_yday + 1 : p->tm_yday) ||
  97                     (lday ==((lday > LEAPDAY) ? p->tm_yday + 1 : p->tm_yday) &&
  98                      ltim <= (p->tm_hour * 100 + p->tm_min)))
  99                         year++;
 100                 else if (lday > LEAPDAY)
 101                         lday--;
 102                 break;
 103         }
 104   sprintf(job, "/usr/spool/at/%02d.%03d.%04d.%02d",
 105         year % 100, lday, ltim, getpid() % 100);
 106   sprintf(pastjob, "/usr/spool/at/past/%02d.%03d.%04d.%02d",
 107         year % 100, lday, ltim, getpid() % 100);
 108   mask= umask(0077);
 109   if ((fp = fopen(pastjob, "w")) == NULL) {
 110         fprintf(stderr, "%s: cannot create %s: %s\n",
 111                 argv[0], pastjob, strerror(errno));
 112         exit(1);
 113   }
 114
 115 /*-------------------------------------------------------------------------*
 116  *      write environment and command(s) to 'at'job file                   *
 117  *-------------------------------------------------------------------------*/
 118   i = 0;
 119   while ((sp= envp[i++]) != NULL) {
 120         dp = buf;
 121         while ((c= *sp++) != '\0' && c != '=' && dp < buf+sizeof(buf)-1)
 122                 *dp++ = c;
 123         if (c != '=') continue;
 124         *dp = '\0';
 125         fprintf(fp, "%s='", buf);
 126         while (*sp != 0) {
 127                 if (*sp == '\'')
 128                         fprintf(fp, "'\\''");
 129                 else
 130                         fputc(*sp, fp);
 131                 sp++;
 132         }
 133         fprintf(fp, "'; export %s\n", buf);
 134   }
 135   fprintf(fp, "cd '%s'\n", pwd);
 136   fprintf(fp, "umask %o\n", mask);
 137   if (argc == 3 || argc == 5)
 138         fprintf(fp, "%s\n", argv[argc - 1]);
 139   else                          /* read from stdinput */
 140         while ((c = getchar()) != EOF) putc(c, fp);
 141   fclose(fp);
 142
 143   if (chown(pastjob, getuid(), getgid()) == -1) {
 144         fprintf(stderr, "%s: cannot set ownership of %s: %s\n",
 145                 argv[0], pastjob, strerror(errno));
 146         unlink(pastjob);
 147         exit(1);
 148   }
 149   /* "Arm" the job. */
 150   if (rename(pastjob, job) == -1) {
 151         fprintf(stderr, "%s: cannot move %s to %s: %s\n",
 152                 argv[0], pastjob, job, strerror(errno));
 153         unlink(pastjob);
 154         exit(1);
 155   }
 156   printf("%s: %s created\n", argv[0], job);
 157
 158   /* Alert cron to the new situation. */
 159   if ((fp= fopen(CRONPID, "r")) != NULL) {
 160         unsigned long pid;
 161
 162         pid= 0;
 163         while ((c= fgetc(fp)) != EOF && c != '\n') {
 164                 if ((unsigned) (c - '0') >= 10) { pid= 0; break; }
 165                 pid= 10*pid + (c - '0');
 166                 if (pid >= 30000) { pid= 0; break; }
 167         }
 168         if (pid > 1) kill((pid_t) pid, SIGHUP);
 169   }
 170   return(0);
 171 }
 172
 173 /*-------------------------------------------------------------------------*
 174  *      getltim()               return((time OK) ? daytime : -1)           *
 175  *-------------------------------------------------------------------------*/
 176 int getltim(t)
 177 char *t;
 178 {
 179   if (t[4] == '\0' && t[3] >= '0' && t[3] <= '9' &&
 180       t[2] >= '0' && t[2] <= '5' && t[1] >= '0' && t[1] <= '9' &&
 181       (t[0] == '0' || t[0] == '1' || (t[1] <= '3' && t[0] == '2')))
 182         return(atoi(t));
 183   else
 184         return(-1);
 185 }
 186
 187 /*-------------------------------------------------------------------------*
 188  *      getlday()               return ((date OK) ? yearday : -1)          *
 189  *-------------------------------------------------------------------------*/
 190 int getlday(m, d)
 191 char *m, *d;
 192 {
 193   int i, day, im;
 194   static int cumday[] = {0, 0, 31, 60, 91, 121, 152,
 195                        182, 213, 244, 274, 305, 335};
 196   static struct date {
 197         char *mon;
 198         int dcnt;
 199   } *pc, kal[] = {
 200         { "Jan", 31 }, { "Feb", 29 }, { "Mar", 31 }, { "Apr", 30 },
 201         { "May", 31 }, { "Jun", 30 }, { "Jul", 31 }, { "Aug", 31 },
 202         { "Sep", 30 }, { "Oct", 31 }, { "Nov", 30 }, { "Dec", 31 },
 203   };
 204
 205   pc = kal;
 206   im = (digitstring(m)) ? atoi(m) : 0;
 207   m[0] &= 0337;
 208   for (i = 1; i < 13 && strcmp(m, pc->mon) && im != i; i++, pc++);
 209   if (i < 13 && (day = (digitstring(d)) ? atoi(d) : 0) && day <= pc->dcnt) {
 210         if (!STARTDAY) day--;
 211         return(day + cumday[i]);
 212   } else
 213         return(-1);
 214 }
 215
 216
 217
 218 int digitstring(s)
 219 char *s;
 220 {
 221   while (*s >= '0' && *s <= '9') s++;
 222   return((*s == '\0') ? 1 : 0);
 223 }