Shows a text file page by page in intervals of N seconds.

reader.sh

#!/usr/bin/bash

#
# Shows a text file page by page in intervals of N seconds. 
#
# If no page is given, it starts in the last page from history.
# 
# Usage:
#
#     ./reader.sh FILE [PAGE] [SECONDS]
#
# Parameters:
# 
#     FILE: a plain text file.
#     PAGE: the number of page to start.
#     SECONDS: the automatic page change interval in seconds. The default is 180 (3 minutes).
#
# Commands:
#
#     p: pause
#     u: page up
#     d: page down
#     q: page down
#     SPACE: next page
#     ENTER: next page
#     ESCAPE: exit
# 
# The commands page up and page down dont log the progress.
# 

[ -f "$1" ] || exit 1;
[ "${2-1}" -ge 1 ] || exit 1;

file="${1}";
page="${2-0}";
secs="${3-180}";
temp=`mktemp`;

if [ ${page} -gt 0 ]; then
	p=${page};
else
	# get the last progress
	touch $HOME/.reader.log
	p=`awk 'END { p = $3 ? $3 : 1; print p }' $HOME/.reader.log`;
fi;

s=0;
t=0;

n=30; # fixed number of lines per page
w=80; # fixed number of characters per page

pageup() {
	[ ${p} -gt 1 ] && p=`expr ${p} \- 1`;
}

pagedn() {
	[ ${p} -le `expr ${max} \/ ${n}` ] && p=`expr ${p} \+ 1`;
}

turnpg() {
	history;
	pagedn;
}

cleanup() {
	rm -f "${temp}";
}

goodbye() {
	echo "";
	echo "Good bye!";
	echo "";
	history;
	cleanup;
	exit 0;
}

history() {
	t=$(expr $(date +"%s") \- ${t})
	# log if more than 10s
	[ $t -le 10 ] && return;
	# History fields: file name, last page number, duration in seconds (>10s)
	echo -e "`date +"%F_%T"`\t`realpath ${file}`\t${p}\t${t}" >> $HOME/.reader.log
}

control() {

	t=$(date +"%s");

	local i=0;
	for i in `seq ${secs} -1 1`; do
		
		# show remaining time
		if [ ${i} -le 30 ]; then
			local j=`expr ${i} \- 1`;
			local time="`date -u -d @${j} +"%T"`";
			printf "\r${time}";
		fi;
		
		read -s -N 1 -t 1 key;
		
		# pause the reading progress
		if [ "$key" = 'p' ] || [ "$key" = 'P' ]; then
			local blinking="\r\033[33;5m%s\033[0m";
			printf "${blinking}" "(PAUSED)";
			read -s -N 1;
			continue;
		fi;
		
		[ -n "$key" ] && break;
		
	done;
	
	[ -z "$key" ] && turnpg;
	
	case $key in
		[uU]   ) pageup;;
		[dD]   ) pagedn;;
		[qQ]   ) goodbye;;
		$'\x20' ) turnpg;; # SPACE
		$'\x0a' ) turnpg;; # ENTER
		$'\e'   ) goodbye;; # ESCAPEl
	esac
}

main() {

	trap goodbye SIGINT

	fold -s -w $w "${file}" > "${temp}";
	max=`wc -l ${temp} | awk '{print $1}'`;

	while true; do
		s=`expr \( ${p} \- 1 \) \* ${n} \+ 1`;
		if [[  ${s} -gt ${max} ]]; then exit 0; fi;
		clear;
		echo;
		echo "- - - - - - - - - - - - - - - - - -";
		echo;
		sed -n "${s},+${n}p" "${temp}";
		echo;
		echo "- - - - - - - - - - - - - - - - - -";
		echo;
		echo "[${p}]";
		echo;
		control;
	done;

}

main;