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Top Forums UNIX for Advanced & Expert Users Use awk to read multiple files twice Post 302605988 by scandy on Friday 9th of March 2012 09:46:34 AM
Old 03-09-2012
Question Use awk to read multiple files twice

Hi folks
I have a situation where I am trying to use awk to compute mean and standard deviation for a variable that spans across multiple files. The layout of each file is same and arranged in 3 columns and uses comma as a delimiter.

Code:
File1 layout:

col1,col2,col3

0,0-1,0.2345
1,1-2,0.3456
1,1-2,0.4567
2,2-3,0.5678

what I need to do is first scan each file (i have at least 200 files) and estimate the global mean of the third column for each index value given in the first colum over all files and then make a repeat pass to calculate the global standard deviation, again for each index value in the first column, over all files and using the global mean I calculated previously.

I thought of using awk for this as my file sizes are big and other scripting languages like Perl or ordinary bash are turning out to be too slow. I did a test and it seems awk can read these huge files line by line really quick but am stuck as to how to implement the actual stuff in awk.

Any help will be very useful.
Thanks
 

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COLRM(1)						    BSD General Commands Manual 						  COLRM(1)

NAME
colrm -- remove columns from a file SYNOPSIS
colrm [start [stop]] DESCRIPTION
The colrm utility removes selected columns from the lines of a file. A column is defined as a single character in a line. Input is read from the standard input. Output is written to the standard output. If only the start column is specified, columns numbered less than the start column will be written. If both start and stop columns are spec- ified, columns numbered less than the start column or greater than the stop column will be written. Column numbering starts with one, not zero. Tab characters increment the column count to the next multiple of eight. Backspace characters decrement the column count by one. ENVIRONMENT
The LANG, LC_ALL and LC_CTYPE environment variables affect the execution of colrm as described in environ(7). EXIT STATUS
The colrm utility exits 0 on success, and >0 if an error occurs. SEE ALSO
awk(1), column(1), cut(1), paste(1) HISTORY
The colrm command appeared in 3.0BSD. BSD
August 4, 2004 BSD
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