UNIX for Advanced & Expert Users

Yes,Author seems to be a UNIX GURU. This is a small part of a Commerical Application.

So you meant to say." I cant do anything other than watch the log growing in size !!"

The problems are

(a) if the program always keeps the file open, eg it does not reopen on SIGHUP or every message or day.

(b) trying to clear it atomically

Two parts to my solution...

1. There is a UNIX API called "truncate" which will set a file to a certain number of bytes.

2. we can suspend and resume the program with signals SIGSTOP and SIGCONT

So the steps are

1. write a tiny C program that wraps up truncate

Code:

#include<unistd.h>
#include <errno.h>
int main(int argc,char **argv) {
int rc=0;
      while (--argc)
      {
            const char *p=*++argv;
            if (truncate(p,0UL)) {
                 perror(p);
                 rc=1;
            }
      }
      return rc;
}

2. do the following

kill -STOP pid-of-process
cp logfilename backup
truncate logfilename
kill -CONT pid-of-process

NO. I meant to say:

Edit the config file, change the log file to another different name.
Send SIGHUP to the process when you are logged in as root.
truncate the old big file.

Try doing
>|log_file