Bash-Beginners-Guide

Bash Guide for Beginners
You picked archive-20030129 (1)
#?
Setting the PS3 prompt and adding a possibility to quit makes it better:
#!/bin/bash
echo "This script can make any of the files in this directory private."
echo "Enter the number of the file you want to protect:"
PS3="Your choice: "
QUIT="QUIT THIS PROGRAM - I feel safe now."
touch "$QUIT"
select FILENAME in *;
do
case $FILENAME in
"$QUIT")
echo "Exiting."
break
;;
*)
echo "You picked $FILENAME ($REPLY)"
chmod go-rwx "$FILENAME"
;;
esac
done
rm "$QUIT"
9.6.2. Submenus
Any statement within a select construct can be another select loop, enabling (a) submenu(s) within a menu.
By default, the PS3 variable is not changed when entering a nested select loop. If you want a different prompt
in the submenu, be sure to set it at the appropriate time(s).
9.7. The shift built-in
9.7.1. What does it do?
The shift command is one of the Bourne shell built-ins that comes with Bash. This command takes one
argument, a number. The positional parameters are shifted to the left by this number, N. The positional
parameters from N+1 to $# are renamed to variable names from $1 to $# - N+1.
Say you have a command that takes 10 arguments, and N is 4, then $4 becomes $1, $5 becomes $2 and so
on. $10 becomes $7 and the original $1, $2 and $3 are thrown away.
If N is zero or greater than $#, the positional parameters are not changed (the total number of arguments, see
Section 7.2.1.2) and the command has no effect. If N is not present, it is assumed to be 1. The return status is
zero unless N is greater than $# or less than zero; otherwise it is non-zero.
Chapter 9. Repetitive tasks 118