Shell Programming and Scripting

Originally Posted by Geneanalyst

Thanks everyone,

Just to clarify, if b.txt has 300 lines, then I would like x =300

Originally Posted by Don Cragun

Come on RudiC and rdrtx1,
In awk $x is the contents of a field in a line and that field might or might not be a number.

Note that the output of the command wc -l b.txt) will be something like:

Code:

    3465 b.txt

if the file b.txt contains 3465 lines (AKA records) of text. With that, the command:

Code:

awk -F "\t" 'NR>5 {if (x==8) print $0}' x=$(wc -l b.txt) a.txt

would invoke awk with the arguments:

Code:

awk -F "\t" 'NR>5 {if (x==8) print $0}' x= 3465 b.txt a.txt

Shell variable assignments only happen in shell command line processing when they occur at the start of a command line. In a shell variable assignment, the leading spaces in the command substitution would be assigned to the variable, but when it appears as a parameter on a command-line after the utility name, the spaces before and after the line count in the output from wc act as field separators.

Hi Geneanalyst,
One might guess that one of the following might do what you requested.

Code:

awk -F '\t' -v x=$(( $(wc -l < b.txt) + 0)) '(NR>5) { if(($x == "0/0")) { print $0} }' a.txt > a1.txt

or:

Code:

awk -F '\t' '
FNR == NR {
	x++
	next
}
(NR + x) > 5 {
	if(($x == "0/0")) { print }
}' b.txt a.txt > a1.txt

or:

Code:

awk -F '\t' '
FNR == NR {
	x++
	next
}
(NR + x) > 5 && $x == "0/0"' b.txt a.txt > a1.txt

One might also guess that you don't really want the awk variable x to be the number of records in b.txt, but instead want it to be the number of fields in that file. If that is what you want, it is even more important than in many other cases to know what operating system and shell you're using because some versions of awk have a nextfile command and others don't.

And, as always, sample input files and desired output would help us help you.

Originally Posted by Geneanalyst

Hi Don,

It just occurred to me that x also happens to be the last column of a.txt. Perhaps it would be easier to assign x to be the last column number of a.txt. Any idea how to do that?