NAME

       nq — job queue utility

SYNOPSIS

       nq [-c] [-q] command line ...
       nq -t job id ...
       nq -w job id ...

DESCRIPTION

       The  nq  utility  provides  a  very  lightweight  queuing  system  without  requiring setup, maintenance,
       supervision or any long-running processes.

       Job order is enforced by a timestamp nq gets immediately when started.  Synchronization happens on  file-
       system  level.   Timer  resolution  is milliseconds.  No sub-second file system time stamps are required.
       Polling is not used.  Exclusive execution is maintained strictly.

       You enqueue(!) new jobs into the queue by running

             nq command line ...

       The job id (a file name relative to NQDIR, which defaults to the current  directory)  is  output  (unless
       suppressed  using  -q)  and nq detaches from the terminal immediately, running the job in the background.
       Standard output and standard error  are  redirected  into  the  job  id  file.   fq(1)  can  be  used  to
       conveniently watch the log files.

       The options are as follows:

       -c      Clean up job id file when process exited with status 0.

       -q      Suppress output of the job id after spawning new job.

       -t      Enter  test  mode:  exit with status 0 when all of the listed job ids are already done, else with
               status 1.

       -w      Enter waiting mode: wait in the foreground until all listed job ids are done.

ENVIRONMENT

       NQDIR   Directory where lock files/job output resides.  Each NQDIR can be considered  a  separate  queue.
               The current working directory is used when NQDIR is unset.  NQDIR is created if needed.

       NQJOBID The job id of the currently running job, exposed to the job itself.

FILES

       nq  owns  all  files  in  NQDIR  (respectively  .) which start with “,” or “.,”.  These files are created
       according to the following scheme:

             ,hexadecimal-time-stamp.pid

EXIT STATUS

       The nq utility exits 0 on success, and >0 if an error occurs; unless test mode is  used,  in  which  case
       exit status 1 means there is a job running.

       On fatal errors, exit codes 111 and 222 are used.

EXAMPLES

       Build make(1) targets clean, depends, all, without occupying the terminal:

             % nq make clean
             % nq make depends
             % nq make all
             % fq
             ... look at output, can interrupt with C-c any time
             without stopping the build ...

       Simple download queue, accessible from multiple terminals:

             % alias qget='NQDIR=/tmp/downloads nq wget'
             % alias qwait='NQDIR=/tmp/downloads fq -q'
             window1% qget http://mymirror/big1.iso
             window2% qget http://mymirror/big2.iso
             window3% qget http://mymirror/big3.iso
             % qwait
             ... wait for all downloads to finish ...

       As  nohup(1)  replacement  (The benchmark will run in background, every run gets a different output file,
       and the command line you ran is logged too.):

             % ssh remote
             remote% nq ./run-benchmark
             ,14f6f3034f8.17035
             remote% ^D
             % ssh remote
             remote% fq
             ... see output, fq exits when job finished ...

TRICKS

       The "file extension" of the log file is actually the PID of the job.  nq runs  all  jobs  in  a  separate
       process  group,  so  you  can  kill an entire job process tree at once using kill(1) with a negative PID.
       Before the job is started, it is the PID of nq, so you can cancel a queued job by killing it as well.

       Thanks to the initial exec line in the log files, you can resubmit a job  by  executing  it  as  a  shell
       command file, i.e. running

             sh job id

       Creating nq wrappers setting NQDIR to provide different queues for different purposes is encouraged.

INTERNALS

       Enforcing job order works like this:
       -   every job has an output file locked using flock(2) and named according to “FILES”.
       -   every job starts only after all earlier flocked files are unlocked.
       -   the lock is released by the kernel after the job terminates.

ASSUMPTIONS

       nq will only work correctly when:

       -   NQDIR (respectively .) is writable.

       -   flock(2) works correctly in NQDIR (respectively .).

       -   gettimeofday(2)  behaves  monotonic  (using  CLOCK_MONOTONIC  would create confusing file names after
           reboot).

       -   No other programs put files matching ,* into NQDIR (respectively .).

SEE ALSO

       fq(1), tq(1).

       Alternatives to the nq system include batch(1), qsub(1), schedule(1), srun(1), and ts(1).

AUTHORS

       Leah Neukirchen <leah@vuxu.org>

CAVEATS

       All reliable queue status information is in main memory only, which makes restarting a job queue after  a
       reboot difficult.

LICENSE

       nq is in the public domain.

       To  the  extent  possible  under  law,  the  creator of this work has waived all copyright and related or
       neighboring rights to this work.

       http://creativecommons.org/publicdomain/zero/1.0/

Debian                                           August 25, 2015                                           NQ(1)