doing var=$( cat file.txt ) prints contents of directory when file contains special characters?

Question

I use a bash script tied to a keyboard shortcut to read a specific chunk of a markdown file, and send that to the api of a shared productivity system (nextcloud deck).

the problem seems to be that there are a bunch of special characters in the file, because it cuts off after a section of a url with /Mting%20Notes&openfile in it

I tried testing this with var=$(cat MUSTDO.txt) and then echo $var in the gnome shell it prints out the contents of the entire directory.

How do I set the variable to the contents of the file, special characters and all, without breaking anything?

here is the full script i use:

#!/bin/bash
#pullout tasks section from local file
awk '/xstart/{flag=1; next} /xend/{flag=0} flag' /home/user1/NotesToSelf/1TASKS_PAD_ALWAYS_VIEW.md > MUSTDO.txt

#set as var, i think this is where things break?
MUSTDO=$(cat MUSTDO.txt)

#send $MUSTDO to nxclouddeck api
curl -X PUT -u username:password \
'https://cloud.example.com/nextcloud/index.php/apps/deck/api/v1.0/boards/11/stacks/12/cards/539' \
-d 'title=Today Tasks' \
-d 'type=plain' \
-d 'owner=username' \
-d "description=$MUSTDO" \
-H "OCS-APIRequest: true" 

I am assuming things break when i set the variable, but I am pretty new to scripting so i really dont know. any resources, advice or suggestions would be appreciated.

EDIT: as i mentioned in a comment, running the script above results in the card i am editing in nextcloud to only display half the content its supposed to. it breaks off after a url with the content: /Mting%20Notes&openfile.

Answer 1

In cross-platform, lowest-common-denominator sh you use:

#!/bin/sh
value=`cat config.txt`
echo "$value"

In bash or zsh, to read a whole file into a variable without invoking cat:

#!/bin/bash
value=$(<config.txt)
echo "$value"