unable to read .db file, returns -1 till the end of the file

[IshaSheikh]

my objective is read a .db file from an SDcard and send it byte/byte through BTclassic. before doing anything I am trying to read the file and print it on the Serial monitor. I am able to get the contents with other types of files but theres some issue when i try to read a .db file. in my code i have tested using a simple txt file(new.txt) and the db file is attendance.db. I am using the serial input from my pc to give input whether to open the txt or the db file. the 'input' variable used in the code is the variable receiving the serial input

[IshaSheikh]

the same .db file reads properly when open with the HEXeditor(tool to view hex for any file in VScode)