Why does grep not stop when end of file is reached?
-f The -f option causes tail to not stop when end of file is reached, but rather to wait for additional data to be appended to the The -f option is ignored if the standard input is a pipe, but not if it is a FIFO. I’d like to only grep for somethingin the tail output. tail -f | grep
When to ignore the F option in tail?
Tail has the following options: -f The -f option causes tail to not stop when end of file is reached, but rather to wait for additional data to be appended to the input. The -f option is ignored if the standard input is a pipe, but not if it is a FIFO. I’d like to only grep for something in the tail output.
When to ignore the F option in grep?
-f The -f option causes tail to not stop when end of file is reached, but rather to wait for additional data to be appended to the input. The -f option is ignored if the standard input is a pipe, but not if it is a FIFO. I’d like to only grep for something in the tail output.
How to get the last match in grep?
So, unless you use grep -m, don’t use tac at all, just parse the output of grep to get the last match: Another approach would be to use Perl or any other scripting language. For example (where $pattern=foo ): doesn’t stop at the first match is because of buffering. Normally, head -n 1 exits after reading a line.
Is there a way to grep a stream?
Yes, this will actually work just fine. Grep and most Unix commands operate on streams one line at a time. Each line that comes out of tail will be analyzed and passed on if it matches. you can check by type alias if this outputs something like tail isan alias of colortail -n 30 . then you have your culprit 🙂
How to grep standard error stream ( stderr )?
If you don’t want to redirect error output to standard output you can redirect error output to a file, then grep it later You may swap the streams. This would enable you to grep the original standard error stream while still getting the output that originally went to standard output in the terminal: