fields(3)
NAME
Sort::Fields - Sort lines containing delimited fields
SYNOPSIS
use Sort::Fields; @sorted = fieldsort [3, '2n'], @lines; @sorted = fieldsort '+', [-1, -3, 0], @lines; $sort_3_2n = make_fieldsort [3, '2n'], @lines; @sorted = $sort_3_2n->(@lines);
DESCRIPTION
Sort::Fields provides a general purpose technique for
efficiently sorting lists of lines that contain data sepa
rated into fields.
Sort::Fields automatically imports two subroutines,
"fieldsort" and "make_fieldsort", and two variants, "sta
ble_fieldsort" and "make_stable_fieldsort". "make_field
sort" generates a sorting subroutine and returns a refer
ence to it. "fieldsort" is a wrapper for the "make_field
sort" subroutine.
The first argument to make_fieldsort is a delimiter
string, which is used as a regular expression argument for
a "split" operator. The delimiter string is optional. If
it is not supplied, make_fieldsort splits each line using
"/".
The second argument is an array reference containing one
or more field specifiers. The specifiers indicate what
fields in the strings will be used to sort the data. The
specifier "1" indicates the first field, "2" indicates the
second, and so on. A negative specifier like "-2" means
to sort on the second field in reverse (descending) order.
To indicate a numeric rather than alphabetic comparison,
append "n" to the specifier. A specifier of "0" means the
entire string ("-0" means the entire string, in reverse
order).
The order in which the specifiers appear is the order in
which they will be used to sort the data. The primary key
is first, the secondary key is second, and so on.
"fieldsort [1, 2], @data" is roughly equivalent to
"make_fieldsort([1, 2])->(@data)". Avoid calling field
sort repeatedly with the same sort specifiers. If you
need to use a particular sort more than once, it is more
efficient to call "make_fieldsort" once and reuse the sub
routine it returns.
"stable_fieldsort" and "make_stable_fieldsort" are like
their "unstable" counterparts, except that the items that
compare the same are maintained in their original order.
EXAMPLES
- Some sample data (in array @data):
- 123 asd 1.22 asdd
32 ewq 2.32 asdd
43 rewq 2.12 ewet
51 erwt 34.2 ewet
23 erww 4.21 ewet
91 fdgs 3.43 ewet
123 refs 3.22 asdd
123 refs 4.32 asdd - # alpha sort on column 1
print fieldsort [1], @data; - 123 asd 1.22 asdd
123 refs 3.22 asdd
123 refs 4.32 asdd
23 erww 4.21 ewet
32 ewq 2.32 asdd
43 rewq 2.12 ewet
51 erwt 34.2 ewet
91 fdgs 3.43 ewet - # numeric sort on column 1
print fieldsort ['1n'], @data; - 23 erww 4.21 ewet
32 ewq 2.32 asdd
43 rewq 2.12 ewet
51 erwt 34.2 ewet
91 fdgs 3.43 ewet
123 asd 1.22 asdd
123 refs 3.22 asdd
123 refs 4.32 asdd - # reverse numeric sort on column 1
print fieldsort ['-1n'], @data; - 123 asd 1.22 asdd
123 refs 3.22 asdd
123 refs 4.32 asdd
91 fdgs 3.43 ewet
51 erwt 34.2 ewet
43 rewq 2.12 ewet
32 ewq 2.32 asdd
23 erww 4.21 ewet - # alpha sort on column 2, then alpha on entire line
print fieldsort [2, 0], @data; - 123 asd 1.22 asdd
51 erwt 34.2 ewet
23 erww 4.21 ewet
32 ewq 2.32 asdd
91 fdgs 3.43 ewet
123 refs 3.22 asdd
123 refs 4.32 asdd
43 rewq 2.12 ewet - # alpha sort on column 4, then numeric on column 1, then
- reverse
# numeric on column 3
print fieldsort [4, '1n', '-3n'], @data; - 32 ewq 2.32 asdd
123 refs 4.32 asdd
123 refs 3.22 asdd
123 asd 1.22 asdd
23 erww 4.21 ewet
43 rewq 2.12 ewet
51 erwt 34.2 ewet
91 fdgs 3.43 ewet - # now, splitting on either literal period or whitespace
# sort numeric on column 4 (fractional part of decimals) - then
# numeric on column 3 (whole part of decimals)
print fieldsort '(?:.|', ['4n', '3n'], @data; - 51 erwt 34.2 ewet
43 rewq 2.12 ewet
23 erww 4.21 ewet
123 asd 1.22 asdd
123 refs 3.22 asdd
32 ewq 2.32 asdd
123 refs 4.32 asdd
91 fdgs 3.43 ewet - # alpha sort on column 4, then numeric on the entire
- line
# NOTE: produces warnings under -w
print fieldsort [4, '0n'], @data; - 32 ewq 2.32 asdd
123 asd 1.22 asdd
123 refs 3.22 asdd
123 refs 4.32 asdd
23 erww 4.21 ewet
43 rewq 2.12 ewet
51 erwt 34.2 ewet
91 fdgs 3.43 ewet - # stable alpha sort on column 4 (maintains original rel
- ative order
# among items that compare the same)
print stable_fieldsort [4], @data; - 123 asd 1.22 asdd
32 ewq 2.32 asdd
123 refs 3.22 asdd
123 refs 4.32 asdd
43 rewq 2.12 ewet
51 erwt 34.2 ewet
23 erww 4.21 ewet
91 fdgs 3.43 ewet
BUGS
Some rudimentary tests now.
- Perhaps something should be done to catch things like:
- fieldsort '.', [1, 2], @lines;
- '.' translates to "split /./" -- probably not what you
want. - Passing blank lines and/or lines containing the wrong kind
of data (alphas instead of numbers) can result in copious
warning messages under "-w". - If the regexp contains memory parentheses ("(...)" rather
than "(?:...)"), split will function in "delimiter reten
tion" mode, capturing the contents of the parentheses as
well as the stuff between the delimiters. I could imagine
how this could be useful, but on the other hand I could
also imagine how it could be confusing if encountered
unexpectedly. Caveat sortor. - Not really a bug, but if you are planning to sort a large
text file, consider using sort(1). Unless, of course,
your operating system doesn't have sort(1).
AUTHOR
Joseph N. Hall, joseph@5sigma.com