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The following is working as expected. (do not want to use nmap) I need to use nc (or any other built-in centOS) command in shell script to check the port 6379 of a remote server. I want the script to exit quickly if no response received in less than 1 second. But it seems that nc will wait for too long before quitting with exit code of 1

How do I "quickly" check if the port is listening?

# time nc -z 1234

real    0m21.001s
user    0m0.000s
sys 0m0.000s

# echo $?

# time nc -z 6379
Connection to 6379 port [tcp/*] succeeded!

real    0m0.272s
user    0m0.000s
sys 0m0.008s

# echo $?
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1 Answer 1

up vote 3 down vote accepted

nc has -w option for tuning the timeout. Try

time nc -w 1 -z 1234
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It's a shame it won't allow less than one second though ... –  David Fraser Mar 7 '13 at 9:44

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