#!/usr/bin/env bash
# Desc: Mixes input lines while also preserving some neighbors
# Usage: cat file | bkshuf arg1
# Version 0.1.2
# Depends: bc 1.07.1, GNU Coreutils 8.32 (shuf)
# Input: var: arg1 initial lines to output
# Load env vars
## For these numbers of lines of input...
if [[ ! -v BKSHUF_PARAM_LINEC ]]; then BKSHUF_PARAM_LINEC=1000000; fi;
## ... target this group size.
if [[ ! -v BKSHUF_PARAM_GSIZE ]]; then BKSHUF_PARAM_GSIZE=25; fi;
yell() { echo "$0: $*" >&2; } # print script path and all args to stderr
die() { yell "$*"; exit 111; } # same as yell() but non-zero exit status
must() { "$@" || die "cannot $*"; } # runs args as command, reports args if command fails
read_stdin() {
# Desc: Consumes stdin; outputs as stdout lines
# Input: stdin (consumes)
# Output: stdout (newline delimited)
# Example: printf "foo\nbar\n" | read_stdin
# Depends: GNU bash (version 5.1.16)
# Version: 0.0.1
local input_stdin output;
# Store stdin
if [[ -p /dev/stdin ]]; then
input_stdin="$(cat -)";
fi;
# Store as output array elements
## Read in stdin
if [[ -n $input_stdin ]]; then
while read -r line; do
output+=("$line");
done < <(printf "%s\n" "$input_stdin");
fi;
# Print to stdout
printf "%s\n" "${output[@]}";
}; # read stdin to stdout lines
checkInt() {
# Desc: Checks if arg is integer
# Usage: checkInt arg
# Input: arg: integer
# Output: - return code 0 (if arg is integer)
# - return code 1 (if arg is not integer)
# Example: if ! checkInt $arg; then echo "not int"; fi;
# Version: 0.0.1
local returnState
#===Process Arg===
if [[ $# -ne 1 ]]; then
die "ERROR:Invalid number of arguments:$#";
fi;
RETEST1='^[0-9]+$'; # Regular Expression to test
if [[ ! $1 =~ $RETEST1 ]] ; then
returnState="false";
else
returnState="true";
fi;
#===Determine function return code===
if [ "$returnState" = "true" ]; then
return 0;
else
return 1;
fi;
} # Checks if arg is integer
consume_line() {
# Desc: Outputs and destroys line from list_input starting at index ip
# Usage: consume_line;
# Input: var: list_input array input lines
# var: lco int line count original
# var: lcr int line count remaining
# var: ip int list_input index pointer
# Output: stdout: a single non-blank element from list_input
# list_input one element destroyed
# var: lc_out incremented once
local n line;
n=0; # for tracking progress iterating through remaining list_input
### Loop once through list_input indices until a non-blank line found
while [[ $n -le $lco ]]; do
#### check if line at ip is blank
line="${list_input[$ip]}";
if [[ -n $line ]]; then
##### consume line at index ip
printf "%s\n" "$line" & # print to output
unset "list_input[$ip]"; # destroy line in list_input array
((lc_out++));
((lcr--)); # decrement line count remaining lcr
#yell "DEBUG:Consumed line ip:$ip:$line";
break;
fi;
#### increment input index pointer, looping around if necessary
if [[ $ip -le $lco ]]; then ((ip++)); else ip=0; fi;
#### track progress through list_input
((n++));
done;
}; # consume and output line in list_input array starting at index ip
decide_read() {
# Desc: Decides whether to read another line in list_input array
# by comparing $RANDOM to p_seq_int
# Usage: if decide_read; then something; fi;
# Input: var: p_seq_int probability (int [0 32767])
if [[ $RANDOM -lt $p_seq_int ]]; then
return 0;
else
return 1;
fi;
}; # returns 0 with probability p_seq; 1 otherwise
main() {
declare par_l0 par_s0 s_exp s;
declare -a list_input;
# Check positional arguments
if [[ $# -gt 0 ]] && ! checkInt "$1"; then
die "FATAL:Not an integer:$1";
else
lc_out_max="$1"; # output line count
fi;
# Check env vars
if ! checkInt "$BKSHUF_PARAM_LINEC"; then
die "FATAL:Not an int:BKSHUF_PARAM_LINEC:$BKSHUF_PARAM_LINEC"; fi;
if ! checkInt "$BKSHUF_PARAM_GSIZE"; then
die "FATAL:Not an int:BKSHUF_PARAM_LINEC:$BKSHUF_PARAM_GSIZE"; fi;
# store input lines from stdin (like `shuf`)
while read -r line; do
if [[ -z $line ]]; then continue; fi; # skip blank lines
#yell "DEBUG:INPUT:$line";
list_input+=("$line");
done < <( read_stdin; );
# calc line count (lc)
lc="${#list_input[@]}";
#lc="$(printf "%s\n" "${list_input[@]}" | wc -l )";
#yell "DEBUG:lc:$lc";
#yell "DEBUG:list_input:$(declare -p list_input)";
# calculate group size s
par_l0="$BKSHUF_PARAM_LINEC";
par_s0="$BKSHUF_PARAM_GSIZE";
s_exp="(( $par_s0 - 1 )/( ( l( $par_l0 ) )^2 ))*(l( $lc ))^2+1";
s="$(echo "scale=12; $s_exp" | bc -l)";
# calculate probabilities p_jump, p_seq
p_jump="$(echo "scale=12; 1 / ( $s )" | bc -l)";
p_seq="$(echo "scale=12; 1 - $p_jump" | bc -l)";
p_seq_int="$(echo "scale=0; ($p_seq * 32767)/1" | bc -l)"; # p_seq as int [0 32767] for $RANDOM range
# generate output
lco="${#list_input[@]}"; # save original input line count
lcr="$lco";
lc_out="0"; # init output line counter
if [[ -z "$lc_out_max" ]]; then lc_out_max="$lco"; fi;
ip="$(shuf -i0-$(( lco - 1 )) -n1)"; # init input index pointer
RANDOM="$(shuf -i0-32767 -n1)"; # init Bash PRNG
n_loop1="0";
#yell "DEBUG:max_blanks:$max_blanks"
while [[ $lcr -ge 1 ]] && [[ $lc_out -lt $lc_out_max ]]; do
## Select random unconsumed input line and consume it to output
ip="$(shuf -i0-$(( lco - 1 )) -n1)"; # init input index pointer
consume_line;
## Consume the next sequential line with probability p_seq.
while decide_read && [[ $lcr -ge 1 ]] && [[ $lc_out -lt $lc_out_max ]]; do
consume_line;
done;
((n_loop1++)); # increment jump counter
done;
#yell "DEBUG:n_loop1:$n_loop1"; # count jumps
}; # main program
main "$@";
# Author: Steven Baltakatei Sandoval
# License: GPLv3+
# Dependency information
# bc 1.07.1
# Copyright 1991-1994, 1997, 1998, 2000, 2004, 2006, 2008, 2012-2017 Free Software Foundation, Inc.
# shuf (GNU coreutils) 8.32
# Copyright (C) 2020 Free Software Foundation, Inc.
# License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
# This is free software: you are free to change and redistribute it.
# There is NO WARRANTY, to the extent permitted by law.
# Written by Paul Eggert.