need to remove duplicates based on key in first column and pattern in last column Post: 302449766

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Top Forums Shell Programming and Scripting need to remove duplicates based on key in first column and pattern in last column Post 302449766 by script_op2a on Tuesday 31st of August 2010 12:33:22 PM

08-31-2010

Registered User

Quote:

Originally Posted by agama

I'm not quite sure what you mean by an if statement cannot be zero.

What I mean is that in order to execute what follows the relational operation of the if statement the value cannot be 0.

For example:

Code:

#!/bin/sh
awk '{split($4,a,"_"); if (b[$1]) {print "this is b[$1]" b[$1]}}' dups.txt

This returns absolutely nothing because b[$1] is 0. Or is it?
Or is it an empty string? How can you tell?

But if you do it like this:
from the working script

Code:

if (b[$1]<=a[4]a[5])

It does NOT evaluate to 0 and continues to what follows the if.

I guess my real question is what value does b[$1] have by itself.

What value does an empty array have in awk when no values has been assigned yet?

If it's 0, I don't understand because how can you say 0>=20100826010517.txt ?

If it IS an empty string when no values have been assigned to it yet then it would be "">=20100826010517.txt . Which I Can understand.

Could you or anyone point me to some online documentation that specifically states if the value is of an empty array 0 or "an empty string" or what it is?
Or a quote from a specific book?

Last edited by Scott; 08-31-2010 at 01:45 PM.. Reason: Code tags

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LEARN ABOUT DEBIAN

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