How to check the first character in a string in Bash or UNIX shell?

How to check the first character in a string in Bash or UNIX shell?

string bash unix character exitstatus

bash

read first 8 characters of text file with bash

file bash character

bash

Get the last 4 characters of output from standard out

linux bash shell character

bash

Find lines in file that contain duplicate characters

bash sorting duplicates character

bash