powerpoint in bash

ppt.sh

#!/bin/bash

usage() {
	echo "Interactively show slides from a file"
	echo
	echo "Usage:"
	echo "$0 FILE LINES"
	echo
	echo "FILE is the file containing the slides."
	echo "In the file, each slide is indicated with a simple 'slide' by itself"
	echo "at the start of a line."
	echo "LINES is the desired height; \$LINES is generally what you want to"
	echo "provide here."
	echo
	echo "Control:"
	echo "Pressing k or h will move backwards one slide."
	echo "Pressing anything else will move ahead one slide."
}

if [ $# -lt 2 ]; then
	usage
	exit 1
fi

UNPARSED="$(cat $1)"
REMOVE_LINES=$(echo "$UNPARSED" | sed '/^slide$/q' | wc -l)
if [ "$REMOVE_LINES" -eq 0 ]; then
	echo "All slides including the first slide must start with 'slide' on a line by itself."
fi
UNPARSED="$(echo "$UNPARSED" | sed -n $((1 + $REMOVE_LINES)),\$p)"

I=0
while [ -n "$UNPARSED" ]; do
	I=$((I + 1))
	SLIDE[$I]="$(echo "$UNPARSED" | sed '/^slide$/q' | sed \$d; echo x)"
	# bash gotcha: command expansion removes trailing newlines
	# we need them here for counting purposes
	# so throw an "x" on the end and take it off after expansion's done
	SLIDE[$I]="${SLIDE[$I]%x}"
	REMOVE_LINES=$(echo "${SLIDE[$I]}" | wc -l)
	UNPARSED="$(echo "$UNPARSED" | sed 1,$(($REMOVE_LINES))d)"
done

echo "Loaded ${#SLIDE[@]} slides"

SLIDE_IX=0
while read -s -N 1; do
	case "$REPLY" in
		[hk])
			GO=-1
			;;
		*)
			GO=1
			;;
	esac
	SLIDE_IX="$(($SLIDE_IX + $GO))"
	if [ "$SLIDE_IX" -gt "${#SLIDE[@]}" ]; then
		SLIDE_IX="${#SLIDE[@]}"
	elif [ "$SLIDE_IX" -lt 1 ]; then
		SLIDE_IX=1
	fi
	echo
	echo -n "${SLIDE[$SLIDE_IX]}"
	SLIDE_HEIGHT="$(echo "${SLIDE[$SLIDE_IX]}" | wc -l)"
	I="$SLIDE_HEIGHT"
	while [ "$I" -lt $2 ]; do
		echo
		I="$(($I + 1))"
	done
done

To clarify, having slides be lines of a single text file is very attractive to me and other solutions have not had that feature

@azriel I'd love to help! This is what i see in man bash on linux
for read -N:

-N nchars
        read returns after reading exactly nchars characters rather than waiting for a complete line of input, unless EOF is encountered or read times out.  Delimiter characters encountered in the input are not treated specially and do not cause read  to  return
        until nchars characters are read.

If your version of bash is missing -N, maybe it has -n which seems more common in the wild and looks like it should also work fine?

@rhowardiv Thanks! Looks like that works great. I'm going to play around with it and I'll let you know if I have any more questions. Thanks for the help!