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How to ensure a process has started reading a file before continuing?

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http://unix.stackexchange.com – I'm trying to write a command to test that data is written to a file. My first approach was: Start reading in the background. Write some data to the file. Wait for the reader to find a result. Repeat indefinitely to see if there's a timing issue. In script form: while true do grep -q foo <(tail -n0 -f /var/log/syslog) & logger foo && logger line && wait done (the logger line command is to avoid last message repeated N times lines in the file) This version will typically loop a once or twice before getting stuck at the wait command, so it looks like tail d (HowTos)

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Submitted by Songlist on 01/17/2013 – Made popular on 01/17/2013

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Please explain what below command does.

logger_cmd="logger -p local0.info ${prog}[$$]:"

$logger_cmd "There are no matching files in ${account_number} for: ${filelist}"

How can I write any message in log file?

I wrote below a command, but it didn't show any message in llog.txt. Help me.

logger -s "any message" -t "WARNING" -f ~/llog.txt

Log files are important when debugging or just to check how a system is performing, we usually use cat to list the log on the screen, but if we want to see a live view of the log file, the command is: tail -f /var/log/logfile.log

$ tail -f /logs/filename.log | awk '!(/list)'

I am able to run this command in GNU Linux flavour

But when I written in a script it is not working.

test.ksh:

variable="/logs/filename.log | awk '!(/list)'" tail -f $var

Getting the error as

tail: cannot open `|' for reading: No such file or directory tail: cannot open `grep' for reading: No such file or directory tail: cannot open `list' fo

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