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Top Forums UNIX for Advanced & Expert Users Last touched file by a specific program ? Post 302926319 by derekludwig on Sunday 23rd of November 2014 09:35:55 AM
Old 11-23-2014
With respect to RudiC, use of a file's access time can be problematic if any other process reads the file, such as backups.

Why 3 programs? Are they three instances of the same program?

If the expense of starting a new process is not onerous, perhaps it would be easier just to use a dispatcher that launches no more than N of your programs:

(pseudo shell code!)
Code:
filescanner | while read file; do
  while [[ ${N} -le $(pgrep appropriateoptions | wc -l) ]]; sleep ${time}; done
  fileomatic ${file} &
done

Or the dispatcher could write a file to one of N named-pipes, one for each fileomatic, something like:

(more pseudo shell code)
Code:
work=$(mktemp -d)

N=0

while read fileomatic; do
  (( N = N + 1 ))
  pipe=${work}/pipe.${N}
  ready=${work}/ready.${N}

  mkfifo ${pipe}

  ${fileomatic} ${ready} < ${pipe} &
done 

filescanner | while read file; do

  while sleep ${delay}; do

    ls -1 ${work}/*.ready | read -aready

    if [[ 0 -lt ${#ready[*]} ]]; then
      i=$(( ${RANDOM} % ${#ready[*]} ))
      n=${ready[$i]}
      echo "${file}" >> ${work}/pipe.${n##*.}
      break
    fi

  done

done

The idea is that the fileomatic will touch the 'ready' file when it can process a file

Last edited by derekludwig; 11-27-2014 at 02:59 PM.. Reason: Typo in arithmantic expression, and some bad logic
 

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io_pipe(3)						     Library Functions Manual							io_pipe(3)

NAME
io_pipe - create a Unix pipe SYNTAX
#include <io.h> int io_pipe(int64 pfd[2]); DESCRIPTION
io_pipe creates a new UNIX ``pipe.'' The pipe can receive data and provide data; any bytes written to the pipe can then be read from the pipe in the same order. A pipe is typically stored in an 8192-byte memory buffer; the exact number depends on the UNIX kernel. Bytes are written to the end of the buffer and read from the beginning of the buffer. Once a byte has been read, it is eliminated from the buffer, making space for another byte to be written; readers cannot ``rewind'' a pipe to read old data. Once 8192 bytes have been written to the buffer, the pipe will not be ready for further writing until some of the bytes have been read. Once all the bytes written have been read, the pipe will not be ready for further reading until more bytes are written. io_pipe sets d[0] to the number of a new descriptor reading from the pipe, and sets d[1] to the number of a new descriptor writing to the pipe. It then returns 1 to indicate success. If something goes wrong, io_pipe returns 0, setting errno to indicate the error; in this case it frees any memory that it allocated for the new pipe, and it leaves d alone. SEE ALSO
io_readfile(3), io_createfile(3), io_socketpair(3) io_pipe(3)
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