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I was wondering why code block was used in this example below:
possibly_hanging_job & { sleep ${TIMEOUT}; eval 'kill -9 $!' &> /dev/null; }
This could have been written like this ( without using code block as well) ..right ?
possibly_hanging_job &
sleep ${TIMEOUT}
eval 'kill -9 $!' &> /dev/null
215
$1 means an input argument and -z means non-defined or empty. You're testing whether an input argument to the script was defined when running the script. Follow this answer to receive notifications.
code:: bash seems to mostly be used in the Cilium docs for interactive shell sessions, although really those should be using something like .. code:: shell-session because they include commands and example output. This is a bit different from straight bash scripts, and the highlighter would treat this better.
$0 is the name of the script itself (script.sh) $1 is the first argument (filename1) $2 is the second argument (dir1)
In your case ## and %% are operators that extract part of the string. ## deletes longest match of defined substring starting at the start of given string. %% does the same, except it starts from back of the string.
Putting the last two commands in braces makes it clear that “These are not just two additional commands that we happen to be running after the long-running process that might hang; they are, instead, integral to getting it shut down correctly before we proceed with the rest of the shell script.” If the author had instead written:
command &
a
b
c
it would not be completely clear that a and b are just part of getting command to end correctly. By writing it like this:
command & { a; b; }
c
the author makes it clearer that a and b exist for the sake of getting command completely ended and cleaned up before the actual next step, c, occurs.
63
Actually I even wonder why there's an eval. As far as I see it should also work without that.
Regarding your actual question:
I guess the code block is there to emphasize that the sleep belongs to kill. But it's not necessary. It should also work like this:
possibly_hanging_job & sleep ${TIMEOUT}; kill -9 $! &> /dev/null
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