September 10th, 2012
In Technology
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If you enjoy this article, see the other most popular articles
If you enjoy this article, see the other most popular articles
If you enjoy this article, see the other most popular articles
How to run shell commands in the background
(written by lawrence krubner, however indented passages are often quotes). You can contact lawrence at: lawrence@krubner.com, or follow me on Twitter.
I have already linked to some interesting shell scripts that launch Java apps. But this is the simplest way to get a Java app up and running from the command line:
Here is how you would need to execute your script/command in order to completely detach it from your session:
sh my_command.sh /dev/null 2>&1 &
Explanation: I have color-coded the command to emphasize the distinct portions of the command. The firsts part (gray) is your unmodified, naked command. The next segment (green) is redirecting standard input (‘<') to read from /dev/null (the null device). The next segment (blue) is redirecting standard output ('>‘ or ‘1>’) to /dev/null. The next segment (red) redirects standard error (‘2>’) to where standard output is being directed (‘&1’). Finally, the ampersand (‘&’) tells the shell to run the command in the background.
You are not required to read from or write to /dev/null. For instance, you will probably want to track the progress of your command by following its output, so you wouldn’t want to send it all into a black hole! Instead, just replace the second (blue) /dev/null with a filename of your choosing. [WARNING: This file will be overwritten if it already exists!!] Let’s say you choose the filename ‘my_logfile’. Now, if your program produces output as it works, you use the ‘tail’ command to check in on how your command is progressing:
tail -f my_logfile
[Just press Ctrl-c to break out of the ‘tail -f’ command.]
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http://command-line.info/blog/?p=119
February 8, 2022 9:33 am
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