This example depends on certain variables that specify the address of the vCenter Server Appliance and credentials to access the appliance.recovery API. For simplicity, the variables are hard-coded at the start of the bash script.

#!/bin/bash
 ##### EDITABLE BY USER to specify vCenter Server instance and credentials. #####
 VC_ADDRESS=vcsa_ip
 VC_USER=sso_user
 VC_PASSWORD=sso_pass
 ############################

 # Authenticate with basic credentials.
 curl -u "$VC_USER:$VC_PASSWORD" \
    -X POST \
    -k --cookie-jar cookies.txt \
    "https://$VC_ADDRESS/rest/com/vmware/cis/session"
 echo ''

 # Issue a request to list the backup file parts.
 curl -k -s --cookie cookies.txt \
     -H 'Accept:application/json' \
     "https://$VC_ADDRESS/rest/appliance/recovery/backup/parts" \
     >response.txt

 # Extract IDs of backup file parts.
 IDs=$(awk '{for (s=$0; match(s,/"id":"\w+"/); s=substr(s,RSTART+RLENGTH)) \
            print substr(s,RSTART+6,RLENGTH-7);}' \
           response.txt)

 # Request sizes of parts.
 echo Backup space required, by part ID:
 let "total=0"
 for ID in $IDs ; do
     curl -k -s --cookie cookies.txt \
         -H 'Accept:application/json' \
         "https://$VC_ADDRESS/rest/appliance/recovery/backup/parts/$ID" \
         >response.txt
     size=$(awk '{if (match($0,/"value":\w+/)) \
                 print substr($0,RSTART+8,RLENGTH-8);}' \
                response.txt)
     printf "  %-8s - %5dMB\n" "$ID" "$size"
     let "total += $size"
 done
 echo ''
 echo "Complete backup file size:  ${total}MB"

 # Clean up temporary files.
 echo ''
 rm -f response.txt
 rm -f cookies.txt