Awk基本入门[5] Awk Associative Arrays

1、Assigning Array Elements

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In Awk, arrays are associative, i.e. an array contains multiple index/value pairs. The index doesn't need to be a continuous set of numbers; in fact it can be a string or a number, and you don't need to specify the size of the array.

Syntax:

arrayname[string]=value

• arrayname is the name of the array.
• string is the index of an array.
• value is any value assigning to the element of the array.

The following is a simple array assignment example:

$ cat array-assign.awk
BEGIN {
　　item[101]="HD Camcorder";
　　item[102]="Refrigerator";
　　item[103]="MP3 Player";
　　item[104]="Tennis Racket";
　　item[105]="Laser Printer";
　　item[1001]="Tennis Ball";
　　item[55]="Laptop";
　　item["na"]="Not Available";
　　print item["101"];
　　print item[102];
　　print item["103"];
　　print item[104];
　　print item["105"];
　　print item[1001];
　　print item[55];
　　print item["na"];
}

$ awk -f array-assign.awk
HD Camcorder
Refrigerator
MP3 Player
Tennis Racket
Laser Printer
Tennis Ball
Laptop
Not Available

Please note the following in the above example:

• Array indexes are not in sequence. It didn't even have to start    from 0 or 1. It really started from 101 .. 105, then jumped to   1001, then came down to 55, then it had a string index "na".
• Array indexes can be string. The last item in this array has an    index string. i.e. "na" is the index.
• You don't need to initialize or even define the array in awk;   you don't need to specify the total array size before you have  to use it.
• The naming convention of an awk array is same as the naming   convention of an awk variable.

From awk's point of view, the index of the array is always a string.Even when you pass a number for the index, awk will treat it as string index. Both of the following are the same.

item[101]="HD Camcorder"
item["101"]="HD Camcorder"