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AWK - BEGIN and END

Actions can be specified to take place prior to the actual start of processing or after it has been completed with BEGIN and END statements respectively.

BEGIN statements are most commonly used to establish variables or display a header.
END statements, on the other hand, can be used to continue processing after the program has finished.

Basic BEGIN Statement

Issue the following command:

awk 'BEGIN {print "NUMBER ITEM QUANTITY PRICE"}' /sharewiz/awk/test2.txt

which will display something like:

NUMBER   ITEM   QUANTITY   PRICE

This would be more useful when run as:

awk 'BEGIN {print "NUMBER ITEM QUANTITY PRICE"}{print NR,$1,$2,$3}' /sharewiz/awk/test2.txt

which will display something like:

NUMBER   ITEM    QUANTITY   PRICE
1 pens 10 1.99
2 pencils 20 3.99
3 staplers 5 8.99
4 rulers 12 2.50

The BEGIN has allowed the header to be added to the output.
The NR variable used in the 2nd print numbers each line. It is a built-in variable of AWK.

Here is a list of some of the built-in variables supported by AWK:

Variable	Details
ARGC	The number of command line arguments.
ARGIND	The index in ARGV of the current file being processed.
ARGV	Array of command line arguments. The array is indexed from 0 to ARGC - 1.
BINMODE	Specifies use of “binary” mode for all file I/O.
CONVFMT	The conversion format for numbers, “%.6g”, by default.
FIELDWIDTHS	A white-space separated list of field widths. When set the input is parsed into fields of fixed width, instead of using the value of the FS variable as the field separator.
FNR	The input record number in the current input file.
FPAT	A regular expression describing the contents of the fields in a record. When set the input is parsed into fields, where the fields match the regular expression, instead of using the value of the FS variable as the field separator.
FS	The input field separator, a space by default.
IGNORECASE	Controls the case-sensitivity of all regular expression and string operations.
NF	The number of fields in the current input record.
NR	The total number of input records seen so far.
OFMT	The output format for numbers, “%.6g”, by default.
OFS	The output field separator, a space by default.
ORS	The output record separator, by default a newline.
RS	The input record separator, by default a newline.
RT	The record terminator.
SUBSEP	The character used to separate multiple subscripts in array elements, by default “\034”.

Basic END Statement

Issue the following command:

awk '{x=x+($2*$3)} END {print "Total Value of Inventory: "x}' /sharewiz/awk/test2.txt

which will display something like:

Total Value of Inventory: 174.65

This would be more useful when run as:

awk '{x=x+($2*$3)} {print $1,"QTY: "$2,"PRICE:"$3,"TOTAL: "$2*$3} END {print "Total Value of Inventory: " x}' /sharewiz/awk/test2.txt

which will display something like:

pens QTY: 10 PRICE:1.99 TOTAL: 19.9
pencils QTY: 20 PRICE:3.99 TOTAL: 79.8
staplers QTY: 5 PRICE:8.99 TOTAL: 44.95
rulers QTY: 12 PRICE:2.50 TOTAL: 30
Total Value of Inventory: 174.65

The END has allowed a total line to be added to the output.
- It is only run at the end.

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Table of Contents

AWK - BEGIN and END

Basic BEGIN Statement

Basic END Statement