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NQ(1) General Commands Manual NQ(1) 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 re- quiring 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 mil- liseconds. 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 cur- rent 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. nqtail(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 di- rectory is used when NQDIR is unset. NQDIR is created if needed. NQDONEDIR When set, specifies a directory (must be on the same file system as NQDIR) where lock files/job output is moved to af- ter successful execution of the job. Ignored when -c is used. NQFAILDIR When set, specifies a directory (must be on the same file system as NQDIR) where lock files/job output is moved to af- ter unsuccessful execution of the job. NQJOBID The job id of the currently running job, exposed to the job itself. FILES nq expects to control 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 termi- nal: % nq make clean % nq make depends % nq make all % nqtail ... 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 nqtail -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% nqtail ... see output, nqtail 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 dif- ferent purposes is encouraged. INTERNALS Enforcing job order works like this: - every job has an output file locked using flock(2) and named ac- cording 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 cre- ate confusing file names after reboot). - No other programs put files matching ,* into NQDIR (respectively .). SEE ALSO nqtail(1), nqterm(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/ FreeBSD Ports 14.quarterly July 3, 2024 NQ(1)
NAME | SYNOPSIS | DESCRIPTION | ENVIRONMENT | FILES | EXIT STATUS | EXAMPLES | TRICKS | INTERNALS | ASSUMPTIONS | SEE ALSO | AUTHORS | CAVEATS | LICENSE
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