rkg

record + knit + grid

One-liner DSL for shell-gei, record processing, and grid-based text transforms.

Description

rkg is a one-liner oriented record/grid processor for text reshaping work.

It combines record-style operations for delimited text with grid-style operations for line-based patterns, so you can select, replace, reshape, transpose, rotate, and otherwise transform structured text from a compact command-line syntax.

For shell-friendly one-liners, the DSL should prefer a small punctuation set built around ., :, ,, ;, and = so that common expressions stay readable in bash/zsh without leaning too heavily on " or ().

Features

• r. / rec. for record mode
• g. / grid. for grid mode
• method chaining with .
• pipeline chaining with |
• statement reset with ;
• AWK-like separators: fs, rs, ofs, ors
• -F / --field-separator for AWK-like initial field separator override
• -R / --record-separator, -O / --output-field-separator, -N / --output-record-separator for initial separator overrides
• field selection, replace, explode, implode, groupby, reshape, flatten
• transpose, rotate, and ray/pattern mark operations for grid input

Install

Cargo Install

cargo install rkg

Build From Source

cargo build --release

Usage

Command

$ rkg --help
Record/grid DSL processor

Quick Start

printf 'A,10;tokyo\nB:20;osaka\n' |
  cargo run -- -F '[,:;]' 'r.p(1,2,3).ofs("|")'

Shorthand:

printf 'A,10;tokyo\nB:20;osaka\n' |
  cargo run -- -F '[,:;]' 'r.p:1,2,3.ofs=|'

Existing commands:

printf 'A,10;tokyo\nB:20;osaka\n' |
  awk -F'[,:;]' '{print $1 "|" $2 "|" $3}'

DSL Shape

r.fs(",").x(2,";").g(1,s(2)).ofs(",");
g.t().rt("r").m(p("K"),"orth","*")

Shorthand forms are also supported for shell-friendly one-liners:

mode.method:arg1,arg2.setting=value;mode.method:arg
mode.method | mode.method
g.t.rt:r

• | pipes the previous stage output into the next stage when the right side starts with r./g.
• method(...) is the classic call form
• method:arg1,arg2 is shorthand for method(arg1,arg2)
• method=value is shorthand for single-argument config-style calls like ofs("|")
• bare method is shorthand for zero-argument calls like t()
• ; resets evaluation to the original stdin for the next statement group
• only the last statement is printed by default
• --print-all prints all statement results separated by ---
• -F sets the initial record-mode fs before the DSL runs, and accepts regex patterns
• -R, -O, and -N set initial rs, ofs, and ors before the DSL runs
• if EXPR is omitted, rkg defaults to record-mode passthrough with the initial CLI separators applied
• when the shell would treat a character specially, quote the whole DSL as one argument

Quick examples

Record functions

-F re / --field-separator re

Sets the initial record-mode field separator from the CLI before any DSL method runs.

Input:

A,10;tokyo
B:20;osaka

Command:

printf 'A,10;tokyo\nB:20;osaka\n' |
  rkg -F '[,:;]' 'r.p(1,2,3).ofs("|")'

Output:

A|10|tokyo
B|20|osaka

Shorthand:

printf 'A,10;tokyo\nB:20;osaka\n' |
  rkg -F '[,:;]' 'r.p:1,2,3.ofs=|'

Existing commands:

printf 'A,10;tokyo\nB:20;osaka\n' |
  awk -F'[,:;]' '{OFS="|"}{print $1,$2,$3}'

Shorthand pipeline chaining

Passes shorthand output from one stage directly into the next stage with |.

Input:

A 10
B 20

Command:

printf 'A 10\nB 20\n' |
  rkg 'r.p:1,2.ofs=- | g.t'

Existing commands:

printf 'A 10\nB 20\n' |
  awk '{s=$1 "-" $2; for(i=1;i<=length(s);i++) col[i]=col[i] substr(s,i,1)} END{for(i=1; i in col; i++) print col[i]}'

Output:

AB
--
12
00

fs(re)

Splits each record with the given regex instead of the default whitespace separator.

Input:

A,10
B,20

Command:

printf 'A,10\nB,20\n' |
  rkg 'r.fs(",")'

Shorthand:

printf 'A,10\nB,20\n' |
  rkg 'r.fs=,'

Option only:

printf 'A,10\nB,20\n' |
  rkg -F,

Existing commands:

printf 'A,10\nB,20\n' |
  awk -F',' '{print $1, $2}'

Output:

A 10
B 20

rs(sep)

Treats the given separator as the boundary between input records.

Input:

A 10|B 20|

Command:

printf 'A 10|B 20|' |
  rkg 'r.rs("|")'

Shorthand:

printf 'A 10|B 20|' |
  rkg 'r.rs=|'

Option only:

printf 'A 10|B 20|' |
  rkg -R'|'

Existing commands:

printf 'A 10|B 20|' |
  awk 'BEGIN{RS="\\|"} NF{print $0}'

Output:

A 10
B 20

Reference

Record functions

• fs(re) input field separator regex, AWK-like (\s+ by default)
• rs(sep) input record separator (\n by default)
• ofs(sep) output field separator ( by default)
• ors(sep) output record separator (\n by default)
• p(...) / select(...) select fields, e.g. p(1,"3:")
• sb(re, rep) / replace(re, rep) regex replace per cell
• n(start_or_AZ) / enum(...) prepend numbering or A-Z cycle labels
• x(col, sep) / explode(...) split one field into multiple rows
• i(key_col, val_col, join_sep?) / implode(...) collapse rows by key
• g(key_col, agg...) / groupby(...) aggregate by key
• sh(mode, ...) / reshape(...) where mode is w2l or l2w
• f(template?) / flatten(...) flatten records; optional template like "{name}:{age}"

Aggregators

• s(col) / sum(col)
• c() / count()
• mn(col) / min(col)
• mx(col) / max(col)
• a(col) / avg(col)
• med(col) / median(col)

Grid functions

• fs(sep) optional cell separator; default is character grid
• rs(sep) / ofs(sep) / ors(sep)
• get(x, y) / get(p(...)) returns a 1-cell grid from a 1-based coordinate or picked point
• set(x, y, value) / set(p(...), value) overwrites one cell at a 1-based coordinate or picked point
• line(origin, dir, values..., wrap(mode)?, skip(n)?) / ln(...) writes values along a direction or fill-mode from a coordinate or picked point
• rev(mode, pad(value)?) / rv(...) reverses the grid horizontally, vertically, or both; pad(...) makes ragged rows rectangular first
• t() / transpose()
• rt("r"|"l"|"180") / rotate(...)
• m(from, ray, put) marks along a ray (orth, diag, alldir, 8); from may be a literal or pick(value[, n]) / p(value[, n])
• m(origin, "line", dir, values..., wrap(mode)?, skip(n)?) can reuse mark as a line-placement mode from one or more origins
• m(from, through_re, to, put) 8-direction pattern mark, useful for reversi-like scans

Shorthand syntax

• r.p:1,3.ofs=| is equivalent to r.p(1,3).ofs("|")
• r.g:1,s:2 is equivalent to r.g(1,s(2))
• g.get:3,2 is equivalent to g.get(3,2)
• g.set:3,2,X is equivalent to g.set(3,2,"X")
• g.rv:h is equivalent to g.rev("h")
• g.rv:h,pad:"." is equivalent to g.rev("h",pad("."))
• g.ln:2,2,r,A,B,C is equivalent to g.line(2,2,"r","A","B","C")
• g.ln:4,1,r,A,B,C,D,wrap:row is equivalent to g.line(4,1,"r","A","B","C","D",wrap("row"))
• g.ln:1,1,fur,A,B,C,D,E,F,G,H,I,skip:1 is equivalent to g.line(1,1,"fur","A","B","C","D","E","F","G","H","I",skip(1))
• g.m:p("K"),line,r,A,B is equivalent to g.m(p("K"),"line","r","A","B")
• g.m:p("K",2),"diag","*" is equivalent to g.m(p("K",2),"diag","*")
• shorthand is most useful for simple one-liners; regular () calls remain available for anything that needs clearer quoting
• the Existing commands snippets below are example-specific equivalents built from common shell tools, not drop-in general replacements for the full DSL

Examples

Record functions

ofs(sep) / output field separator

Changes the separator used when fields are joined for output.

Input:

A 10
B 20

Command:

printf 'A 10\nB 20\n' |
  rkg 'r.ofs(",")'

Shorthand:

printf 'A 10\nB 20\n' |
  rkg 'r.ofs=,'

Option only:

printf 'A 10\nB 20\n' |
  rkg -O,

Existing commands:

printf 'A 10\nB 20\n' |
  awk '{$1=$1; OFS=","; print}'

Output:

A,10
B,20

ors(sep) / output record separator

Changes the separator used when output records are joined together.

Input:

A 10
B 20

Command:

printf 'A 10\nB 20\n' |
  rkg 'r.ors("|")'

Shorthand:

printf 'A 10\nB 20\n' |
  rkg 'r.ors=|'

Option only:

printf 'A 10\nB 20\n' |
  rkg -N'|'

Existing commands:

printf 'A 10\nB 20\n' |
  awk 'BEGIN{ORS="|"} {print $0}'

Output:

A 10|B 20|

p(...) / select(...)

Keeps only the requested fields and removes the rest.

Input:

A 10 tokyo
B 20 osaka

Command:

printf 'A 10 tokyo\nB 20 osaka\n' |
  rkg 'r.p(1,3)'

Shorthand:

printf 'A 10 tokyo\nB 20 osaka\n' |
  rkg 'r.p:1,3'

Existing commands:

printf 'A 10 tokyo\nB 20 osaka\n' |
  awk '{print $1, $3}'

Output:

A tokyo
B osaka

sb(re, rep) / replace(re, rep)

Replaces text matching the regex in every cell.

Input:

A-10
B-20

Command:

printf 'A-10\nB-20\n' |
  rkg 'r.sb("[0-9]","X")'

Shorthand:

printf 'A-10\nB-20\n' |
  rkg 'r.sb:[0-9],X'

Existing commands:

printf 'A-10\nB-20\n' |
  sed -E 's/[0-9]/X/g'

Output:

A-XX
B-XX

n(start_or_AZ) / enum(...)

Adds a numeric counter column to the front of each row.

Input:

A 10
B 20

Command:

printf 'A 10\nB 20\n' |
  rkg 'r.n(1)'

Shorthand:

printf 'A 10\nB 20\n' |
  rkg 'r.n:1'

Existing commands:

printf 'A 10\nB 20\n' |
  awk '{print NR, $0}'

Output:

1 A 10
2 B 20

Uses alphabet labels instead of numbers and prepends them as a new first column.

Input:

A 10
B 20
C 30

Command:

printf 'A 10\nB 20\nC 30\n' |
  rkg 'r.n("A-Z")'

Shorthand:

printf 'A 10\nB 20\nC 30\n' |
  rkg 'r.n:A-Z'

Existing commands:

printf 'A 10\nB 20\nC 30\n' |
  awk '{printf "%c %s\n", 64 + NR, $0}'

Output:

A A 10
B B 20
C C 30

x(col, sep) / explode(...)

Splits one field into multiple rows while keeping the other columns as-is.

Input:

A,10;20;30
B,7;8

Command:

printf 'A,10;20;30\nB,7;8\n' |
  rkg -F, -O, 'r.x(2,";")'

Shorthand:

printf 'A,10;20;30\nB,7;8\n' |
  rkg -F, -O, 'r.x:2,";"'

Existing commands:

printf 'A,10;20;30\nB,7;8\n' |
  awk -F',' '{n=split($2, a, ";"); for (i=1; i<=n; i++) print $1 "," a[i]}'

Output:

A,10
A,20
A,30
B,7
B,8

i(key_col, val_col, join_sep?) / implode(...)

Merges rows with the same key by joining one value column into a single field.

Input:

A 10
A 20
A 30
B 7
B 8
B 9
C 100
C 200

Command:

printf 'A 10\nA 20\nA 30\nB 7\nB 8\nB 9\nC 100\nC 200\n' |
  rkg 'r.i(1,2,",")'

Shorthand:

printf 'A 10\nA 20\nA 30\nB 7\nB 8\nB 9\nC 100\nC 200\n' |
  rkg 'r.i:1,2,","'

Existing commands:

printf 'A 10\nA 20\nA 30\nB 7\nB 8\nB 9\nC 100\nC 200\n' |
  awk '!seen[$1]++{keys[++n]=$1} {vals[$1]=vals[$1] ? vals[$1] "," $2 : $2} END {for (i=1; i<=n; i++) print keys[i], vals[keys[i]]}'

Output:

A 10,20,30
B 7,8,9
C 100,200

g(key_col, agg...) / groupby(...)

Groups rows by the key column and emits aggregate results per group.

Input:

A,10;20;30
B,7;8

Command:

printf 'A,10;20;30\nB,7;8\n' |
  rkg -F, -O, 'r.x(2,";").g(1,s(2))'

Shorthand:

printf 'A,10;20;30\nB,7;8\n' |
  rkg  -F, -O, 'r.x:2,";".g:1,s:2'

Existing commands:

printf 'A,10;20;30\nB,7;8\n' |
  awk -F'[,;]' '{if (!seen[$1]++) keys[++n]=$1; for (i=2; i<=NF; i++) sum[$1]+=$i} END {for (i=1; i<=n; i++) print keys[i] "," sum[keys[i]]}'

Output:

A,60
B,15

sh("w2l", ...) / reshape(...)

Turns wide columns into repeated long-form rows.

Input:

name math eng
A 80 90
B 70 85

Command:

printf 'name math eng\nA 80 90\nB 70 85\n' |
  rkg 'r.sh("w2l",2)'

Shorthand:

printf 'name math eng\nA 80 90\nB 70 85\n' |
  rkg 'r.sh:w2l,2'

Existing commands:

printf 'name math eng\nA 80 90\nB 70 85\n' |
  awk 'NR==1{for (i=2; i<=NF; i++) h[i]=$i; next} {for (i=2; i<=NF; i++) print $1, h[i], $i}'

Output:

A math 80
A eng 90
B math 70
B eng 85

sh("l2w", ...) / reshape(...)

Turns repeated long-form rows back into a wide table.

Input:

A math 80
A eng 90
B math 70
B eng 85

Command:

printf 'A math 80\nA eng 90\nB math 70\nB eng 85\n' |
  rkg 'r.sh("l2w",2,3)'

Shorthand:

printf 'A math 80\nA eng 90\nB math 70\nB eng 85\n' |
  rkg 'r.sh:l2w,2,3'

Existing commands:

printf 'A math 80\nA eng 90\nB math 70\nB eng 85\n' |
  sort -k2,2 -k1,1 |
  awk 'BEGIN{OFS=" "} !c[$2]++{col[++m]=$2} !r[$1]++{row[++n]=$1} {a[$1,$2]=$3} END{printf "key"; for(i=1;i<=m;i++) printf OFS col[i]; print ""; for(j=1;j<=n;j++){printf row[j]; for(i=1;i<=m;i++) printf OFS a[row[j],col[i]]; print ""}}'

Output:

key eng math
A 90 80
B 85 70

f(template?) / flatten(...)

Renders each data row as a single string using the header names in the template.

Input:

name age
alice 20
bob 30
carol 25
dave 41

Command:

printf 'name age\nalice 20\nbob 30\ncarol 25\ndave 41\n' |
  rkg 'r.f("{name}:{age}")'

Shorthand:

printf 'name age\nalice 20\nbob 30\ncarol 25\ndave 41\n' |
  rkg 'r.f:"{name}:{age}"'

Existing commands:

printf 'name age\nalice 20\nbob 30\ncarol 25\ndave 41\n' |
  awk 'NR>1 {print $1 ":" $2}'

Output:

alice:20
bob:30
carol:25
dave:41

Aggregators

s(col) / sum(col)

Sums the numeric values in the target column for each group.

Input:

A 10
A 20
B 7

Command:

printf 'A 10\nA 20\nB 7\n' |
  rkg 'r.g(1,s(2))'

Shorthand:

printf 'A 10\nA 20\nB 7\n' |
  rkg 'r.g:1,s:2'

Existing commands:

printf 'A 10\nA 20\nB 7\n' |
  awk '{c[$1]+=$2} END {for (k in c) print k, c[k]}' | sort

# or, with datamash:
printf 'A 10\nA 20\nB 7\n' |
  datamash -s -g 1 sum 2

Output:

A 30
B 7

c() / count()

Counts how many rows belong to each group.

Input:

A 10
A 20
B 7

Command:

printf 'A 10\nA 20\nB 7\n' |
  rkg 'r.g(1,c())'

Shorthand:

printf 'A 10\nA 20\nB 7\n' |
  rkg 'r.g:1,c'

Existing commands:

printf 'A 10\nA 20\nB 7\n' |
  awk '{print $1}' | uniq -c | awk '{print $2, $1}'

# or, with datamash:
printf 'A 10\nA 20\nB 7\n' |
  datamash -s -g 1 count 1

Output:

A 2
B 1

mn(col) / min(col)

Takes the smallest numeric value in the target column for each group.

Input:

A 10
A 20
A 15
B 7
B 12
C 3
C 9

Command:

printf 'A 10\nA 20\nA 15\nB 7\nB 12\nC 3\nC 9\n' |
  rkg 'r.g(1,mn(2))'

Shorthand:

printf 'A 10\nA 20\nA 15\nB 7\nB 12\nC 3\nC 9\n' |
  rkg 'r.g:1,mn:2'

Existing commands:

printf 'A 10\nA 20\nA 15\nB 7\nB 12\nC 3\nC 9\n' |
  sort -k1,1 -k2,2n | awk '!a[$1]++'

# or, with datamash:
printf 'A 10\nA 20\nA 15\nB 7\nB 12\nC 3\nC 9\n' |
  datamash -s -g 1 min 2

Output:

A 10
B 7
C 3

mx(col) / max(col)

Takes the largest numeric value in the target column for each group.

Input:

A 10
A 20
A 15
B 7
B 12
C 3
C 9

Command:

printf 'A 10\nA 20\nA 15\nB 7\nB 12\nC 3\nC 9\n' |
  rkg 'r.g(1,mx(2))'

Shorthand:

printf 'A 10\nA 20\nA 15\nB 7\nB 12\nC 3\nC 9\n' |
  rkg 'r.g:1,mx:2'

Existing commands:

printf 'A 10\nA 20\nA 15\nB 7\nB 12\nC 3\nC 9\n' |
  sort -k1,1 -k2,2nr | awk '!a[$1]++'

# or, with datamash:
printf 'A 10\nA 20\nA 15\nB 7\nB 12\nC 3\nC 9\n' |
  datamash -s -g 1 max 2

Output:

A 20
B 12
C 9

a(col) / avg(col)

Computes the average numeric value in the target column for each group.

Input:

A 10
A 20
A 15
B 7
B 12
C 3
C 9

Command:

printf 'A 10\nA 20\nA 15\nB 7\nB 12\nC 3\nC 9\n' |
  rkg 'r.g(1,a(2))'

Shorthand:

printf 'A 10\nA 20\nA 15\nB 7\nB 12\nC 3\nC 9\n' |
  rkg 'r.g:1,a:2'

Existing commands:

printf 'A 10\nA 20\nA 15\nB 7\nB 12\nC 3\nC 9\n' |
  awk '{sum[$1]+=$2; cnt[$1]++} END {for (k in sum) print k, sum[k] / cnt[k]}' |
  sort

# or, with datamash:
printf 'A 10\nA 20\nA 15\nB 7\nB 12\nC 3\nC 9\n' |
  datamash -s -g 1 mean 2

Output:

A 15
B 9.5
C 6

med(col) / median(col)

Computes the median numeric value in the target column for each group.

Input:

A 10
A 20
A 15
B 7
B 12
C 3
C 9

Command:

printf 'A 10\nA 20\nA 15\nB 7\nB 12\nC 3\nC 9\n' |
  rkg 'r.g(1,med(2))'

Shorthand:

printf 'A 10\nA 20\nA 15\nB 7\nB 12\nC 3\nC 9\n' |
  rkg 'r.g:1,med:2'

Existing commands:

printf 'A 10\nA 20\nA 15\nB 7\nB 12\nC 3\nC 9\n' |
  awk '{a[$1][++n[$1]]=$2} END {for (k in a) {asort(a[k]); print k, n[k]%2 ? a[k][(n[k]+1)/2] : (a[k][n[k]/2]+a[k][n[k]/2+1])/2}}' |
  sort

# or, with datamash:
printf 'A 10\nA 20\nA 15\nB 7\nB 12\nC 3\nC 9\n' |
  datamash -s -g 1 median 2

Output:

A 15
B 9.5
C 6

Grid functions

fs(sep) / cell separator

Treats each input row as separator-delimited cells instead of a character grid.

Input:

a,b,c
d,e,f

Command:

printf 'a,b,c\nd,e,f\n' |
  rkg -O'|' 'g.fs(",")'

Shorthand:

printf 'a,b,c\nd,e,f\n' |
  rkg -O'|' 'g.fs=,'

Existing commands:

printf 'a,b,c\nd,e,f\n' |
  awk -F',' '{print $1 "|" $2 "|" $3}'

Output:

a|b|c
d|e|f

rs(sep) / record separator

Treats the given separator as the boundary between grid rows.

Input:

abc|def|ghi|

Command:

printf 'abc|def|ghi|' |
  rkg 'g.rs("|")'

Shorthand:

printf 'abc|def|ghi|' |
  rkg 'g.rs=|'

Option only:

printf 'abc|def|ghi|' |
  rkg -R'|'

Existing commands:

printf 'abc|def|ghi|' |
  awk 'BEGIN{RS="\\|"} NF {print $0}'

Output:

abc
def
ghi

ofs(sep) / output field separator

Changes the separator used when cells are joined for each output row.

Input:

abc
def

Command:

printf 'abc\ndef\n' |
  rkg 'g.ofs("|")'

Shorthand:

printf 'abc\ndef\n' |
  rkg 'g.ofs=|'

Option only:

printf 'abc\ndef\n' |
  rkg -O'|'

Existing commands:

printf 'abc\ndef\n' |
  sed 's/./&|/g; s/|$//'

Output:

a|b|c
d|e|f

ors(sep) / output record separator

Changes the separator used when output rows are joined together.

Input:

abc
def

Command:

printf 'abc\ndef\n' |
  rkg 'g.ors("---\n")'

Shorthand:

printf 'abc\ndef\n' |
  rkg 'g.ors="---\n"'

Option only:

printf 'abc\ndef\n' |
  rkg -N'---\n'

Existing commands:

printf 'abc\ndef\n' |
  awk 'BEGIN{ORS="---\n"} {print $0}'

Output:

abc---
def---

t() / transpose()

Swaps rows and columns in the grid.

Input:

abc
def
ghi

Command:

printf 'abc\ndef\nghi\n' |
  rkg 'g.t()'

Shorthand:

printf 'abc\ndef\nghi\n' |
  rkg 'g.t'

Existing commands:

printf 'abc\ndef\nghi\n' |
  awk '{for (i=1; i<=length($0); i++) col[i]=col[i] substr($0, i, 1)} END {for (i=1; i in col; i++) print col[i]}'

Output:

adg
beh
cfi

rt("r"|"l"|"180") / rotate(...)

Rotates the grid 90 degrees clockwise.

Input:

abc
def
ghi

Command:

printf 'abc\ndef\nghi\n' |
  rkg 'g.rt("r")'

Shorthand:

printf 'abc\ndef\nghi\n' |
  rkg 'g.rt:r'

Existing commands:

printf 'abc\ndef\nghi\n' |
  awk '{rows[NR]=$0; if (length($0)>w) w=length($0)} END {for (i=1; i<=w; i++) {out=""; for (j=NR; j>=1; j--) out = out substr(rows[j], i, 1); print out}}'

Output:

gda
heb
ifc

Rotates the grid by 180 degrees.

Input:

abc
def
ghi

Command:

printf 'abc\ndef\nghi\n' |
  rkg 'g.rt("180")'

Shorthand:

printf 'abc\ndef\nghi\n' |
  rkg 'g.rt=180'

Existing commands:

printf 'abc\ndef\nghi\n' |
  awk '{rows[NR]=$0} END {for (i=NR; i>=1; i--) {out=""; for (j=length(rows[i]); j>=1; j--) out = out substr(rows[i], j, 1); print out}}'

Output:

ihg
fed
cba

m(from, ray, put) / mark(from, ray, put)

Marks all reachable cells along the specified ray directions from the source cell. from can be a literal cell value or pick(value[, n]) / p(value[, n]), which selects the nth matching cell in top-to-bottom, left-to-right order.

Input:

.......
.......
...K...
.......
.......

Command:

printf '.......\n.......\n...K...\n.......\n.......\n' |
  rkg 'g.m(p("K"),"orth","*")'

Nth match:

printf 'K....\n.....\n..K..\n.....\n....K\n' |
  rkg 'g.m(p("K",2),"diag","*")'

Existing commands:

printf '.......\n.......\n...K...\n.......\n.......\n' |
  awk '{rows[NR]=$0; if ((p=index($0,"K"))>0) {ky=NR; kx=p}} END {for (y=1; y<=NR; y++) {out=""; for (x=1; x<=length(rows[y]); x++) {c=substr(rows[y], x, 1); if ((y==ky || x==kx) && !(y==ky && x==kx) && c==".") c="*"; out=out c} print out}}'

Output:

...*...
...*...
***K***
...*...
...*...

Nth match output:

*...*
.*.*.
..K..
.*.*.
*...*

m(from, through_re, to, put) / mark(from, through_re, to, put)

Marks only the matching middle cells when they are sandwiched between from and to.

Input:

.......
.......
.XOOOX.
.......
.......

Command:

printf '.......\n.......\n.XOOOX.\n.......\n.......\n' |
  rkg 'g.m("X","O","X","*")'

Shorthand:

printf '.......\n.......\n.XOOOX.\n.......\n.......\n' |
  rkg 'g.m:X,O,X,*'

Existing commands:

printf '.......\n.......\n.XOOOX.\n.......\n.......\n' |
  sed 's/XOOOX/X***X/'

Output:

.......
.......
.X***X.
.......
.......

rev(mode, pad(value)?) / rv(mode, pad(value)?)

Reverses the grid horizontally, vertically, or both. Use mode as h, v, or hv. If rows have different widths, pad(value) can make them rectangular before reversing.

Input:

abc
def
ghi

Command:

printf 'abc\ndef\nghi\n' |
  rkg 'g.rev("h")'

Shorthand:

printf 'abc\ndef\nghi\n' |
  rkg 'g.rv:h'

Output:

cba
fed
ihg

Pad example:

printf 'ab\ncde\n' |
  rkg 'g.rev("h",pad("."))'

Shorthand:

printf 'ab\ncde\n' |
  rkg 'g.rv:h,pad:"."'

Output:

.ba
edc

line(origin, dir, values..., wrap(mode)?, skip(n)?) / ln(origin, dir, values..., wrap(mode)?, skip(n)?)

Writes values along a direction or fill-mode from a coordinate or picked point. One-way directions are right / r, left / l, up / u, down / d, ur, ul, dr, dl. Centered directions are horiz / h, vert / v, diag_dr / xr, and diag_dl / xl, and they require an odd number of values so the middle value lands on the origin. Fill modes are fill_ur / fur and fill_ul / ful. wrap(mode) is optional and only works for one-way directions:

• r / l with wrap("row")
• u / d with wrap("col")
• dr / ul with wrap("diag_dr")
• dl / ur with wrap("diag_dl")

skip(n) is optional and only works for fill modes. It skips the first n cells in the fill traversal before writing values.

Input:

.....
.....
.....

Command:

printf '.....\n.....\n.....\n' |
  rkg 'g.line(2,2,"r","A","B","C")'

Shorthand:

printf '.....\n.....\n.....\n' |
  rkg 'g.ln:2,2,r,A,B,C'

Wrapped shorthand:

printf '.....\n.....\n.....\n' |
  rkg 'g.ln:4,1,r,A,B,C,D,wrap:row'

Output:

.....
.ABC.
.....

Diagonal example:

printf '.....\n.....\n.....\n.....\n.....\n' |
  rkg 'g.line(2,2,"dr","C","O","D","E")'

Output:

.....
.C...
..O..
...D.
....E

Diagonal shorthand:

printf '.....\n.....\n.....\n.....\n.....\n' |
  rkg 'g.ln:2,2,dr,C,O,D,E'

Diagonal wrap example:

printf '.....\n.....\n.....\n.....\n.....\n' |
  rkg 'g.ln:3,3,dr,A,B,C,D,wrap:diag_dr'

Output:

.D...
.....
..A..
...B.
....C

Top-edge diagonal example: Coordinates are 1-based, so the top-left corner is (1,1).

printf '.....\n.....\n.....\n.....\n.....\n' |
  rkg 'g.ln:1,1,dr,H,E,L,L,O'

Output:

H....
.E...
..L..
...L.
....O

Second-row diagonal example:

printf '.....\n.....\n.....\n.....\n.....\n' |
  rkg 'g.ln:1,2,dr,S,L,A,N'

Output:

.....
S....
.L...
..A..
...N.

Fill-mode example:

printf '.....\n.....\n.....\n.....\n.....\n' |
  rkg 'g.ln:1,1,fur,A,B,C,D,E,F,G,H,I,skip:1'

Existing commands:

printf '.....\n.....\n.....\n.....\n.....\n' |
  awk 'BEGIN{split("A B C D E F G H I", vals, " ")} {rows[NR]=$0} END {skip=1; n=0; for (d=0; d<10; d++) {for (x=0; x<=d; x++) {y=d-x; if (x<5 && y<5) cells[++n]=(x+1) "," (y+1)}} for (i=skip+1; i<=n && i-skip<=length(vals); i++) {split(cells[i], p, ","); x=p[1]; y=p[2]; row=rows[y]; rows[y]=substr(row,1,x-1) vals[i-skip] substr(row,x+1)} for (y=1; y<=5; y++) print rows[y]}'

Output:

.BEI.
ADH..
CG...
F....
.....

Shifted fill-mode example:

printf '.....\n.....\n.....\n.....\n.....\n' |
  rkg 'g.ln:1,1,fur,A,B,C,D,E,F,G,skip:3'

Output:

..CG.
.BF..
AE...
D....
.....

You can also route the same behavior through mark mode:

printf '.....\n..K..\n.....\n' |
  rkg 'g.m:p("K"),line,r,A,B'

Multiple byte example:

seq -f 'printf "　%%.s" {1..10};echo # %g' 1 7 |
  bash |
  rkg 'g.ln:1,1,fur,'$(echo "ウンコとこの子とボディビルそしてチンコ"|sed 's/\B/,/g')',skip:1' |
  sed 's/$/\$/g'

Output:

　ンこボそ　　　　　$
ウととルコ　　　　　$
コ子ビン　　　　　　$
のィチ　　　　　　　$
デて　　　　　　　　$
し　　　　　　　　　$
　　　　　　　　　　$

Multiple statements

Runs each statement against the original stdin, so later statements do not receive earlier output.

Input:

A 10,20
B 7,8

Command:

printf 'A 10,20\nB 7,8\n' |
  rkg --print-all 'r.x(2,",").g(1,s(2)); r.n(1)'

Shorthand:

printf 'A 10,20\nB 7,8\n' |
  rkg --print-all 'r.x:2,",".g:1,s:2; r.n:1'

Existing commands:

{ printf 'A 10,20\nB 7,8\n' | awk '{split($2, a, ","); print $1, a[1] + a[2]}'; printf '%s\n' '---'; printf 'A 10,20\nB 7,8\n' | awk '{print NR, $0}'; }

Output:

A 30
B 15
---
1 A 10,20
2 B 7,8

Notes

• fs is treated as a regex for record mode, similar to AWK FS
• CSV quoting is not implemented; this prototype is regex-split based
• ; resets to the original stdin; it does not pass the previous statement result to the next one
• grid mode defaults to character cells; g.fs(",") switches to separated cells