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linuxbashgrepdaemontee

tee command not working when run in background

I want a daemon that continuously watches a named pipe for input, and then creates two files: one that contains all the data that went through the named pipe, and one that contains a filtered version of it.

When I run this command from the command line it works as intended, $ACTIONABLE_LOG_FILE is created as a filtered version of $LOG_FILE_BASENAME:

cat $NAMED_PIPE | tee -a "$LOG_FILE_BASENAME" | grep -P -v "$EXCEPTIONS" >> "$ACTIONABLE_LOG_FILE" &

But when I leave the following code running in the background, nothing gets appended to $ACTIONABLE_LOG_FILE:

while true
do
   cat $NAMED_PIPE | tee -a "$LOG_FILE_BASENAME" | grep -P -v "$EXCEPTIONS" >> "$ACTIONABLE_LOG_FILE" &
   wait $!
done

The file $ACTIONABLE_LOG_FILE gets created, but nothing gets appended to it. What's going on here?

Solution

  • My suspicion would be that when daemonized, you do not have a full environment available, and hence no $PATH. The full path to the command (likely /usr/bin/tee) might help a lot. You can confirm that locally with which tee.