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Top Forums UNIX for Advanced & Expert Users How to read a fast written log file at Real time speed? Post 302937623 by cool.aquarian on Friday 6th of March 2015 03:15:47 PM
Old 03-06-2015
Hi there..

I managed to improve the performance by 10-fold for real time reading.

I analysed and found that most time was being taken by
Code:
while IFS= read -r line

I replaced the while loop with awk to read a single logical unit(each about 6000 lines) in one go.

Code:
tail -F --lines=10000000 --retry --max-unchanged-stats=10 "$FILE_NAME" | awk -f awk-script.txt

Now the speed of reading is able to more than keep up with speed of write.
Even when the file gets rolled over, it is able to catch-up with the new file and gives message like:
tail: `<file-name>' has been replaced; following end of new file

Last edited by cool.aquarian; 03-06-2015 at 06:40 PM..
 

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IGAWK(1)							 Utility Commands							  IGAWK(1)

NAME
igawk - gawk with include files SYNOPSIS
igawk [ all gawk options ] -f program-file [ -- ] file ... igawk [ all gawk options ] [ -- ] program-text file ... DESCRIPTION
Igawk is a simple shell script that adds the ability to have ``include files'' to gawk(1). AWK programs for igawk are the same as for gawk, except that, in addition, you may have lines like @include getopt.awk in your program to include the file getopt.awk from either the current directory or one of the other directories in the search path. OPTIONS
See gawk(1) for a full description of the AWK language and the options that gawk supports. EXAMPLES
cat << EOF > test.awk @include getopt.awk BEGIN { while (getopt(ARGC, ARGV, "am:q") != -1) ... } EOF igawk -f test.awk SEE ALSO
gawk(1) Effective AWK Programming, Edition 1.0, published by the Free Software Foundation, 1995. AUTHOR
Arnold Robbins (arnold@skeeve.com). ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +--------------------+-----------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +--------------------+-----------------+ |Availability | SUNWgawk | +--------------------+-----------------+ |Interface Stability | Volatile | +--------------------+-----------------+ NOTES
Source for gawk is available on http://opensolaris.org. Free Software Foundation Nov 3 1999 IGAWK(1)
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