Sort associative array with AWK

Question

Here\'s my array (gawk script) :

myArray[\"peter\"] = 32
myArray[\"bob\"] = 5
myArray[\"john\"] = 463
myArray[\"jack\"] = 11

After sort, I

Answer 1

PROCINFO["sorted_in"] = "@val_num_desc";

Before iterating an array, use the above statement. But, it works in awk version 4.0.1. It does not work in awk version 3.1.7.

I am not sure in which intermediate version, it got introduced.

Answer 2

Use asorti:

#!/usr/bin/env -S gawk -f
{
    score[$1] = $0;
    array[sprintf("%3s",$2) $1] = $1;
}

END {
    asorti(array, b)
    for(i in b)
    {
        name = array[b[i]]
        print score[name]
    }
}

Answer 3

The authors of The Awk Programming Language provide a quicksort function, which is available online.

I think you'd do something like this.

END {
  for (key in myArray) {
    sortkeys[j++] = key;
  }
  qsort(sortkeys, 0, length(myArray));      # Not sure I got the args right.
  for (i = 1; i <= length(myArray); i++) {
    print sortkeys[i], myArray[sortkeys[i]];
  }
}

Answer 4

And the simple answer...

function sort_by_myArray(i1, v1, i2, v2) {
    return myArray[i2] < myArray[i1];
}

BEGIN {
    myArray["peter"] = 32;
    myArray["bob"] = 5;
    myArray["john"] = 463;
    myArray["jack"] = 11;
    len = length(myArray);

    asorti(myArray, k, "sort_by_myArray");

    # Print result.
    for(n = 1; n <= len; ++n) {
            print k[n], myArray[k[n]]
    }
}

Answer 5

Use the Unix sort command with the pipe, keeps Awk code simple and follow Unix philosophy
Create a input file with values seperated by comma
peter,32
jack,11
john,463
bob,5

Create a sort.awk file with the code

BEGIN { FS=","; }
{
    myArray[$1]=$2;
}
END {
    for (name in myArray)
        printf ("%s,%d\n", name, myArray[name]) | "sort -t, -k2 -n"
}

Run the program, should give you the output
$ awk -f sort.awk data
bob,5
jack,11
peter,32
john,463

Answer 6

Edit:

Sort by values

Oh! To sort the values, it's a bit of a kludge, but you can create a temporary array using a concatenation of the values and the indices of the original array as indices in the new array. Then you can asorti() the temporary array and split the concatenated values back into indices and values. If you can't follow that convoluted description, the code is much easier to understand. It's also very short.

# right justify the integers into space-padded strings and cat the index
# to create the new index
for (i in myArray) tmpidx[sprintf("%12s", myArray[i]),i] = i
num = asorti(tmpidx)
j = 0
for (i=1; i<=num; i++) {
    split(tmpidx[i], tmp, SUBSEP)
    indices[++j] = tmp[2]  # tmp[2] is the name
}
for (i=1; i<=num; i++) print indices[i], myArray[indices[i]]

Edit 2:

If you have GAWK 4, you can traverse the array by order of values without performing an explicit sort:

#!/usr/bin/awk -f
BEGIN {
    myArray["peter"] = 32
    myArray["bob"] = 5
    myArray["john"] = 463
    myArray["jack"] = 11

    PROCINFO["sorted_in"] = "@val_num_asc"

    for (i in myArray) {
        {print i, myArray[i]}}
    }

 }

There are settings for traversing by index or value, ascending or descending and other options. You can also specify a custom function.

Previous answer:

Sort by indices

If you have an AWK, such as gawk 3.1.2 or greater, which supports asorti():

#!/usr/bin/awk -f
BEGIN {
    myArray["peter"] = 32
    myArray["bob"] = 5
    myArray["john"] = 463
    myArray["jack"] = 11

    num = asorti(myArray, indices)
    for (i=1; i<=num; i++) print indices[i], myArray[indices[i]]
}

If you don't have asorti():

#!/usr/bin/awk -f
BEGIN {
    myArray["peter"] = 32
    myArray["bob"] = 5
    myArray["john"] = 463
    myArray["jack"] = 11

    for (i in myArray) indices[++j] = i
    num = asort(indices)
    for (i=1; i<=num; i++) print i, indices[i], myArray[indices[i]]
}