How to make tail display only the lines that have a specific text?

shell unix tail
blagus picture blagus · Aug 15, 2013 · Viewed 19.9k times · Source

How to make tail display only the lines that have a specific text? If the search criteria can be a regular expression, it would be even better. I need something like:

tail -f mylogfile.log showOnlyLinesWith "error: "

I am running Darwin (Mac OS X) and I'm totally beginner in the bash.

Answer

arghbleargh picture arghbleargh · Aug 15, 2013

You can do

tail -f mylogfile.log | grep "error: "

This works with regular expressions too. In general, you can take the output of any command, add | to "pipe" it to grep, and let grep filter out the lines that don't match a certain pattern.

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