我想在特定时间运行R代码

Question

我想在我需要的特定时间运行R代码.在完成该过程后,我想终止R会话.

如果代码如下,

tm<-Sys.time()
write.table(tm,file='OUT.TXT', sep='\t');
quit(save = "no")

我应该怎么做才能在"2012-04-18 17:25:40"运行此代码.我需要你的帮助.提前致谢.

Answer 1

最简单的方法是使用Windows 的Task Scheduler或Linux下的cron作业.在那里,您可以指定应在指定的特定时间运行的命令或程序.我绝对不会推荐R脚本:

time_to_run = as.POSIXct("2012-04-18 17:25:40")
while(TRUE) {
   Sys.sleep(1)
   if(Sys.time == time_to_run) {
     ## run some code
   }
}

Answer 2

如果以某种方式您无法使用cron作业服务并且必须在R中安排,则以下R代码显示如何等待特定时间量以便在预先指定的目标时间执行.

stop.date.time.1 <- as.POSIXct("2012-12-20 13:45:00 EST") # time of last afternoon execution. 
stop.date.time.2 <- as.POSIXct("2012-12-20 7:45:00 EST") # time of last morning execution.
NOW <- Sys.time()                                        # the current time
lapse.time <- 24 * 60 * 60              # A day's worth of time in Seconds
all.exec.times.1 <- seq(stop.date.time.1, NOW, -lapse.time) # all of afternoon execution times. 
all.exec.times.2 <- seq(stop.date.time.2, NOW, -lapse.time) # all of morning execution times. 
all.exec.times <- sort(c(all.exec.times.1, all.exec.times.2)) # combine all times and sort from recent to future
cat("To execute your code at the following times:\n"); print(all.exec.times)

for (i in seq(length(all.exec.times))) {   # for each target time in the sequence
  ## How long do I have to wait for the next execution from Now.
  wait.time <- difftime(Sys.time(), all.exec.times[i], units="secs") # calc difference in seconds.
  cat("Waiting for", wait.time, "seconds before next execution\n")
  if (wait.time > 0) {
    Sys.sleep(wait.time)   # Wait from Now until the target time arrives (for "wait.time" seconds)
    {
      ## Put your execution code or function call here
    }
  }
}