UNIX for Dummies Questions & Answers

hi guys,

I perform a sort of monitoring. I have a server running and with

Code:

tail -f | grep "Searchstring"

I monitor the log-file for recent specific entries. This is ok and works fine.

Now, in addition I want to have my search results not posted into the shell but into a file. I tried:

Code:

tail -f | grep "Searchstring" > output.txt

Code:

tail -f | grep "Searchstring" >> output.txt

Code:

tail -f  > output.txt

works but has no "grep" statement.

Would be very nice if you could help me out.
thx in advance

This is because of output buffering. If you have GNU grep you can try:

Code:

grep --line-buffered

If not you could try:

Code:

tail -f log-file |
while IFS= read -r line
do
  case $line in
    (*"Searchstring"*) printf "%s\n" "$line"
  esac
done > output.txt

That might be due to buffering. On linux, one of the coreutils is stdbuf that allows to modify the way programs use their input and output buffers. Try:

Code:

tail -f /var/log/syslog | stdbuf -o0 grep "Searchstring" > output.txt &

Rudi,
you are my hero of the day....it works like a charm...
I just put the tail-command into a screen-session and it keeps logging everything of the search string into the file...

thx very much for you help....I do very appreciate it!
cheers