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My script (.ksh) :
cmd1 & cmd2
I want cmd1 to be executed in the background and cmd2 to start executing only after cmd1 has started. But, when I run my script, cmd2 is starting before cmd1, thereby causing me a problem.
How can I solve this issue ?
The easiest solution would to add a tiny sleep:
cmd1 & sleep 1 && cmd2
More robust would be to use a wrapper for cmd2 that makes sure the cmd1 is actually running and then proceed.
Something like:
while ! pgrep cmd1; do
sleep 1
done
cmd2
while ! can be replaced with until BTW.
cmd2. You need to create a script with this, and it will run cmd2 only when cmd1 is running.
– heemayl
Aug 2 '17 at 9:47
By using the conditional operator && you can force the "finish" of one execution before the other one starts. (I put "finish" in quotes, because what is actually "finishing" is putting the process in the background.)
While
$ (echo "foo" &) ; echo "bar"
might output
bar
foo
the following
$ (echo "foo" &) && echo "bar"
will output
foo
bar
because the shell needs to determine the exit status of the first command before it can execute the second.
