Unix command line queue utility
github.com $ mkfifo ~/.jobqueue
$ parallel :::: ~/.jobqueue
echo ls > ~/.jobqueue
for a remote job queue, use nc instead of a fifo
for a job queue with a buffer, use a file, and run $ parallel :::: <(tail -f thefile) you can even truncate the file from time to time.
Of course, this doesn't capture the context you are in, such as your current directory or the value of shell variables.
Here is an alternative:
And then, in another terminal:tty1$ mkfifo /tmp/jobqueue tty1$ eval $(tail -n 1 /tmp/jobqueue)tty2$ echo ls > /tmp/jobqueueWhat's 'parallel'? Is it a *nix command? Looks like its not available on Fedora box
Yes, it's a GNU tool. Try "yum install parallel".
This stackoverflow answer[0] shows how you can queue jobs even after you start running other processes in your queue. Essentially, you can do:
sleep 2; echo "A" && sleep 2 ; echo "B" && sleep 2 ; echo "C"
# Quickly Ctrl-Z
fg && sleep 2 ; echo "D"
Could you please add some usage examples or elaborate on when this tool would be useful? For example,
> building several targets of a Makefile
As opposed to `make && sudo make install` ?
> downloading multiple files one at a time
As opposed to `(wget url1 &) ; (wget url2 &)` ?
> or simply as a glorified `nohup`
As opposed to `nohup` ?
I imagine it's useful if you don't know all the commands you want to queue at the beginning.
For example:
nq ./my_awesome_analysis /data/complicated_file_with_long_name.dat # um... what's the next file? ls /data nq ./my_awesome_analysis /data/even_more_complicated_path.dat man rsync nq rsync -avh --progress out* somewhere_else.net:You don't need nq for that. Just kick off ./my_lame_analysis in the background whenever you want.
Yes but then they will execute at the same time instead of sequentially.
How about:
./my_awesome_analysis /data/complicated_file_with_long_name.dat & # do some stuf wait ./my_awesome_analysis /data/even_more_complicated_path.datIt's still not equivalent, and it's more cumbersome.
Thank you for making the comment I came to make!
The shells have had queueing for, well, a very, very long time....
Which systems guarantee monotonic behavior for gettimeofday()? I can't think of any. I hope there's no behavior in nq which relies on monotonicity other than file naming, because otherwise you might run into some obscure issues.
How does this differ from task spooler:
cat list.txt | xargs -n 1 -P 20 wget
Queues up 20 concurrent downloads with wget, for example.
You could also use a for loop. But as others pointed out, that doesn't allow you to add items to the queue after it has started.
It does if you use a fifo instead of a text file. This is the difference between basic Unix literacy and actual Unix proficiency. I'm not being insulting; very few people take the time to learn the tools Unix provides. And naturally, a developer is going to be more interested in writing tools than most.
I don't think you can use a fifo with xargs, though it'd definitively work with a loop. Even with text files, using tail -f.
tail -n+0 -f list.txt | xargs -n 1 -P 20 wget