Why no output is shown when using grep twice?

by

You might also run into a problem with grep buffering when inside a pipe.
ie, you don’t see the output from 

   tail --follow=name file.txt | grep something > output.txt

since grep will buffer its own output.

Use the –line-buffered switch for grep to work around this:

tail --follow=name file.txt | grep --line-buffered something > output.txt

This is useful if you want to get the results of the follow into the output.txt file as rapidly as possible.

More Related Contents:

  1. How can I search for a multiline pattern in a file?
  2. How can I remove the BOM from a UTF-8 file? [duplicate]
  3. How do I find all files containing specific text on Linux?
  4. How do I send a file as an email attachment using Linux command line?
  5. What’s the magic of “-” (a dash) in command-line parameters?
  6. What is double dot(..) and single dot(.) in Linux?
  7. What does the number in parentheses shown after Unix command names in manpages mean?
  8. Automatically capture output of last command into a variable using Bash?
  9. Quickly create a large file on a Linux system
  10. How to find out line-endings in a text file?
  11. How do I use the lines of a file as arguments of a command?
  12. Linux command to print directory structure in the form of a tree
  13. Using grep to get the next WORD after a match in each line
  14. How can I generate a list of files with their absolute path in Linux?
  15. How to create a file with a given size in Linux?
  16. How to concatenate multiple lines of output to one line?
  17. How to get the process ID to kill a nohup process?
  18. Pipe output to bash function
  19. GROUP BY/SUM from shell
  20. How to recursively download a folder via FTP on Linux [closed]
  21. How to reset Jenkins security settings from the command line?
  22. How to search and replace using grep
  23. grep without showing path/file:line
  24. How to search contents of multiple pdf files?
  25. How to find directory of some command?
  26. How do you search for files containing DOS line endings (CRLF) with grep on Linux?
  27. How do you filter out all unique lines in a file?
  28. View tabular file such as CSV from command line [closed]
  29. How can I get the resolution (width and height) for a video file from a linux command line?
  30. Linux shell script to add leading zeros to file names

Leave a Comment