Linux Shell Scripting Tutorial (LSST) v1.05r3
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Predefined variable of awk

Our next example talks more about predefined variable of awk. Create awk file as follows:

$cat > def_var
 {
 print "Printing Rec. #" NR "(" $0 "),And # of field for this record is " NF
 }

Run it as follows.
$awk -f def_var inven
Printing Rec. #1(1. Pen 5 20.00),And # of field for this record is 4
Printing Rec. #2(2. Pencil 10 2.00),And # of field for this record is 4
Printing Rec. #3(3. Rubber 3 3.50),And # of field for this record is 4
Printing Rec. #4(4. Cock 2 45.50),And # of field for this record is 4

NR and NF are predefined variables of awk which means Number of input Record, Number of Fields in input record respectively. In above example NR is changed as our input record changes, and NF is constant as there are only 4 field per record. Following table shows list of such built in awk variables.

awk Variable	Meaning
FILENAME	Name of current input file
RS	Input record separator character (Default is new line)
OFS	Output field separator string (Blank is default)
ORS	Output record separator string (Default is new line)
NF	Number of input record
NR	Number of fields in input record
OFMT	Output format of number
FS	Field separator character (Blank & tab is default)


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