Exec

https://man7.org/linux/man-pages/man1/exec.1p.html

Open YOUR_FILE_TO_READ as file descriptor 3 for reading:
exec 3< YOUR_FILE_TO_READ

exec $SHELL

exec in Bash

Related commands

• tail
• exec mount option.
• flock

See also

• Bash [ -c ], alias, &&, Bash history, Autocompletion, set, unset, export, .bash_aliases, .bashrc and .bash profile, PS1, echo, brace expansion, Function, shopt, trap, set -e, source, PATH, complete, disown, .hushlogin, .bashrc, builtin, eval, set, $PATH, $HOME, TZ, .profile, -e, -i, Builtin (Bash), mapfile, ~, return (Bash), for, until, declare, dirname, basename, functions.sh, Bash arithmetic expansion, shift, bash --rcfile, readonly, $1, $@

https://askubuntu.com/questions/525767/what-does-an-exec-command-do