mjhjmtu

I am getting confused here how to do this. Say I want to make a script that asks how many tracks in a cd and then asks for the track name that many times with each track formatted and exported to a file. I tried this so far but its wrong.

#!/bin/bash

read -p 'How many tracks are there?' TRACKCOUNT
#while not amount of tracks
TRACK=1
while [ $TRACK -le $TRACKCOUNT ]
do
#indirection not a good idea?
#http://mywiki.wooledge.org/BashFAQ/006#Indirection
#ask for track<count> title save to variable TTITLE
read -p 'Track '$(($TRACK + 1))': ' TTITLE
TTITLE="$TTITLE:-No Name"
set TTITLE$TRACK=TTITLE
echo $!TTITLE$TRACK
(( TRACK++ ))
done

What I expect to get is a file such as:

TTITLE1=Uptown Funk!
TTITLE2=Thinking Out Loud
TTITLE3=See You Again

what i get is line 14: $!TTITLE$TRACK: bad substitution
and set | grep TITLE returns nothing so no variable is being set (I think).

UPDATE:

To print to a file as you indicate, here's an updated script:

#!/bin/bash
read -p 'How many tracks are there?' TRACKCOUNT
TRACK=1
while [ $TRACK -le $TRACKCOUNT ]
do
 read -p "Track $TRACK: " TTITLE
 echo "TTITLE$TRACK=$TTITLE:-No Name" >> ./track_output.txt
 (( TRACK++ ))
done

To answer the title of your question, fixing your script to work, and going that little bit farther to spit the results into an array indexed by track number (per your comment):

#!/bin/bash
declare -a TRACK_ARRAY
read -p 'How many tracks are there?' TRACKCOUNT
TRACK=1
while [ $TRACK -le $TRACKCOUNT ]
do
 read -p "Track $TRACK: " TTITLE
 TRACK_ARRAY[$TRACK]="$TTITLE:-No Name"
 (( TRACK++ ))
done

echo "$TRACK_ARRAY[*]"

This takes your input and loops through, correctly asking for TRACK1 through TRACKN where N is the number entered by the user. At the end I simply print all indices of the array, since I have no idea how you are utilizing it. This page is a start (from TLDP) on how you might work with that array in bash

You were indexing incorrectly (would have caught that quickly once you got it to run), but another problem you had was that you were trying to assign a variable name which itself had a $ contained within it: set TTITLE$TRACK=TTITLE - this will not create a variable named TTITLE# where # is the value of $TRACK. I can't confidently tell you what this does.

When trying to use that variable you did this: echo $!TTITLE$TRACK, in which the bang (!) is actually a bang command trying to find the most recent command starting with TTITLE... (not what you intended).

Whenever you find yourself trying to dynamically assign variable names, you should ask yourself if there's a higher-order data structure that can solve your problem. In other words, keep data out of your variable names. I think arrays are a good solution.

Commenting to cunninghamp3's answer I realised I don't need to use variables or arrays I can just list everything into a file simply step by step. This is what I ended up with.

#!/bin/bash
i=1
#clear the template file and start blank
echo "#Template file of CD Tracks"> ./template.txt
read -p 'How many tracks are there?' TRACKCOUNT
while [ $i -le $TRACKCOUNT ]
do
read -p 'Track '$i': ' TRACK
TRACK="$TRACK:-Track #"$i""
echo ""TTITLE"$((i-1))"="$TRACK" >> ./template.txt
(( i++ ))
done

get the user to write the track titles into a file, one per line.

in your script read the titles into an array:

mapfile -t titles < track_title_file.txt

then process the elements. For example:

for index in "$!titles[@]"; do
 printf "TITLE%d=%sn" "$index" "$titles[index]"
done