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Full Discussion: Shell script to apply functions to multiple columns dynamically
Top Forums Shell Programming and Scripting Shell script to apply functions to multiple columns dynamically Post 303025730 by bakunin on Saturday 10th of November 2018 07:30:45 PM
Old 11-10-2018
Quote:
Originally Posted by mkathi
say if i want multiple columns based on the header example id,name or id,age or name,gender and hash and store the output value in a new column for each row
If you want multiple columns you need to make the variable target_id and target_idx both arrays, no?

Then there is this:
Code:
  # then, iterate over lines
  while IFS=, read -r -a line; do
    a=echo-n ${line[$target_idx]}|md5sum # if my input in target is "id"
  done
} <testfile.txt

echo$line|"$a"

You iterate over the input lines, yes, but you produce output (the echo-line) only once: after you have read all the input. This must be wrong, no? Apart from the fact that after "echo" there needs to be a space (like after any command), but i suppose that was simply a typing error.

Also this line is not correct:
Code:
a=echo-n ${line[$target_idx]}|md5sum # if my input in target is "id"

It should perhaps read:
Code:
a=$(echo -n ${line[$target_idx]}|md5sum) # if my input in target is "id"

For parametrisation via the commandline i suggest to read the man page for getopts. I have just written an example in another thread you might want to use as a starting point.

I hope this helps.

bakunin
 

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LEARN ABOUT OSX

colrm

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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