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Fri, 25 Jun 2010

/Coding/bash: Add a Timestamp to Your Logging

Suppose you have various bits of code executing in cron, sending their output to user-defined log files, ie. some cron entries as follows,

*/2 * * * * /path/to/a/script.sh >> /some/logging/directory/cron.output 2>&1

and you want a generalized way of tagging each log entry with a time stamp. The solution is fairly simple, but the bits are sufficiently hard to track down and not all available in one place, so I thought I would document it.... Create this script, lets call it timestamp.sh:

#!/bin/bash
# this script prepends a time stamp to the first line of piped input.

stamp=$(date "+%F %R:%S")
echo -n $stamp
echo -n " "

while read line; do
   # print the first line of piped input
   echo ${line[0]}
done

and then use a cron entry as follows:

*/2 * * * * /path/to/a/script.sh 2>&1 | /path/to/timestamp.sh >> /logging/directory/cron.output 2>&1

Ie. The output of script.sh is piped to timestamp.sh, where the first line is prepended with the timestamp, and then the time-stamped line is added to cron.output. Thanks to [1].

[1] http://www.linuxquestions.org/questions/linux-software-2/bash-scripting-pipe-input-to-script-vs-$1-570945/

posted at: 16:19 | path: /Coding/bash | permanent link to this entry

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Fri, 25 Jun 2010