Count (count)

Count items in a map, list or array

Description

Counts the number of items in a structure, be that a list, map or other object type.

count has several modes ranging from updating values in place, returning new structures, or just outputting totals.

Usage

<stdin> -> count [ --duplications | --unique | --total ] -> <stdout>

Examples

Count number of items in a map, list or array:

» tout json (["a", "b", "c"]) -> count 
3

Flags

• --bytes Count the total number of bytes read from stdin
• --duplications Output a JSON map of items and the number of their occurrences in a list or array
• --runes Count the total number of unicode characters (runes) read from stdin. Zero width symbols, wide characters and other non-typical graphemes are all each treated as a single rune
• --sum Read an array, list or map from stdin and output the sum of all the values (ignore non-numeric values)
• --sum-strict Read an array, list or map from stdin and output the sum of all the values (error on non-numeric values)
• --total Read an array, list or map from stdin and output the length for that array (default behaviour)
• --unique Print the number of unique elements in a list or array
• -b

Alias for --bytes

• -d Alias for --duplications
• -r Alias for --runes
• -s Alias for --sum
• -t Alias for --total
• -u Alias for --unique

Detail

If no flags are set, count will default to using --total.

Total: --total / -t

This will read an array, list or map from stdin and output the length for that array.

» a [25-Dec-2020..05-Jan-2021] -> count 
12

This also replaces the older len method.

Please note that this returns the length of the array rather than string. For example out "foobar" -> count would return 1 because an array in the str data type would be new line separated (eg out "foo\nbar" -> count would return 2). If you need to count characters in a string and are running POSIX (eg Linux / BSD / OSX) then it is recommended to use wc instead. But be mindful that wc will also count new line characters.

» out "foobar" -> count
1

» out "foo\nbar" -> count
2

» out "foobar" -> wc: -c
7

» out "foo\nbar" -> wc: -c
8

» printf "foobar" -> wc: -c
6
# (printf does not print a trailing new line)

Duplications: --duplications / -d

This returns a JSON map of items and the number of their occurrences in a list or array.

For example in the quote below, only the word "the" is repeated so that entry will have a value of 2 while ever other entry has a value of 1 because they only appear once in the quote.

» out "the quick brown fox jumped over the lazy dog" -> jsplit \s -> count --duplications
{
    "brown": 1,
    "dog": 1,
    "fox": 1,
    "jumped": 1,
    "lazy": 1,
    "over": 1,
    "quick": 1,
    "the": 2
}

Unique: --unique / -u

Returns the number of unique elements in a list or array.

For example in the quote below, only the word "the" is repeated, thus the unique count should be one less than the total count:

» out "the quick brown fox jumped over the lazy dog" -> jsplit \s -> count --unique
8
» out "the quick brown fox jumped over the lazy dog" -> jsplit \s -> count --total
9

Synonyms

• count
• len

See Also

• Append To List (append): Add data to the end of an array
• Create JSON Array (ja): A sophisticated yet simply way to build a JSON array
• Create Map (map): Creates a map from two data sources
• Create New Array (ta): A sophisticated yet simple way to build an array of a user defined data-type
• Filter By Range [ ..Range ]: Outputs a ranged subset of data from stdin
• Get Item ([ Index ]): Outputs an element from an array, map or table
• Get Nested Element ([[ Element ]]): Outputs an element from a nested structure
• Output With Type Annotation (tout): Print a string to the stdout and set it's data-type
• Prepend To List (prepend): Add data to the start of an array
• Reverse Array (mtac): Reverse the order of an array
• Sort Array (msort): Sorts an array - data type agnostic
• Split String (jsplit): Splits stdin into a JSON array based on a regex parameter
• Split String (jsplit): Splits stdin into a JSON array based on a regex parameter
• Stream New List (a): A sophisticated yet simple way to stream an array or list (mkarray)

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This document was generated from builtins/core/datatools/count_doc.yaml.