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How to capture results of a watch in a file

  • Feb 19 / 2015
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Linux

How to capture results of a watch in a file

For debugging purposes, it can sometimes be useful to write the results of a command executed at a given time lapse. You can easily monitor a command by using the watch command.

By default a watch command is only displaying result, and you have to be in front of to see the results. If you want to write them in a file with a timestamp, you can easily do it by using this command that combines  a watch command with tee:

# watch -t -n 1 "(date '+TIME:%H:%M:%S' ; netstat -np | egrep -i *:443) | tee -a /tmp/logfilewatch"

You can now open your file /tmp/logfilewatch and see the results you just got!
For example, here is what you could get with my previous command, checking all the connections on port TCP 443:

TIME:22:24:22
tcp        0      0 0.0.0.0:443             0.0.0.0:*               LISTEN      1722/apache2
TIME:22:24:23
tcp        0      0 0.0.0.0:443             0.0.0.0:*               LISTEN      1722/apache2
TIME:22:24:35
tcp        0      0 192.168.100.250:443       12.34.56.78:27911     TIME_WAIT   -
TIME:22:24:36
tcp        0      0 192.168.100.250:443       12.34.56.78:27911     TIME_WAIT   -
TIME:22:24:37
tcp        0      0 192.168.100.250:443       12.34.56.78:27911     TIME_WAIT   -
TIME:22:24:38
tcp        0      0 192.168.100.250:443       12.34.56.78:27911     TIME_WAIT   -
TIME:22:24:39
tcp        0      0 192.168.100.250:443       12.34.56.78:27916     SYN_RECV    -
tcp        0      0 192.168.100.250:443       12.34.56.78:27911     TIME_WAIT   -
TIME:22:24:41
tcp        0      0 192.168.100.250:443       12.34.56.78:27916     ESTABLISHED 16810/apache2
tcp        0      0 192.168.100.250:443       12.34.56.78:27911     TIME_WAIT   -
TIME:22:24:42
tcp        0      0 192.168.100.250:443       12.34.56.78:27916     ESTABLISHED 16810/apache2
tcp        0      0 192.168.100.250:443       12.34.56.78:27911     TIME_WAIT   -

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