Hello,

Please help about writing a process that will be automatically notified by file creation in a predefined directory. Some code will appreciated.

Thanks for all.

#!/bin/sh

while [ 1 ]; do                        # Run for as long as nessesary
  if [ -f /some/where/a/file ]; then   # If filename exists and has the apropriate name
    echo "File is found"               # Notify and stop monitoring
    exit 0
  fi
  sleep 60                             # Else wait a minut and see again
done

The brute force methods will work, but many systems today provide better ways to watch for file changes. I've listed some ideas at Monitoring file or directory changes

Hello and thank you for these answers.

To clarify a little more the subject, the problem isn't to write a program which wakes up every n seconds to analyze if there is something under a directory. But to make a subscription to be notified by an event and to fall asleep until the arrival of the asynchronous event like "FILE ADDED".

Are you talking about writing a program to monitor a FIFO pipe so the program will sleep untill another program activates the pipe then the first program will wake up and do it's bit ?

Here's a small C section to do that

#include <stdio.h>
#include <time.h>
#include <sys/types.h>
#include <sys/stat.h>

int main(void)
{
  FILE* fp;
  time_t t;
  const char * file = "my_fifo_fil";
  if (mkfifo(file, 0644) == -1)
    {
      printf("Error initializing fifo    %s\n", file);
      return -1;
    }
  if(!(fp = fopen(file, "w")))
    {
      printf("Error opening fifo %s\n", file);
      return -1;
    }
  t = time(NULL);
  if(fprintf(fp,"Program Woken at: %s\n", ctime(&t)) < 0)
    {
      printf("Error printing to fifo %s\n", file);
      return -1;
    }
  printf("You woke me poking my fifo %s\n", file);
  if(close(fp) == -1)
    {
      printf("Error closing fifo %s\n", file);
      return -1;
    }
  if(unlink(file) == -1)
    {
      printf("Error unlinking fifo %s\n", file);
      return -1;
    }
  return 0;
}

redhead@sindre{56} ~/Programming> ./a.out & [1] 5035 redhead@sindre{57} ~/Programming> cat my_fifo_fil You woke me poking my fifo my_fifo_fil Program Woken at: Tue Nov 10 17:38:40 2009 [1] Done ./a.out