USER INPUT

Read command  – The read command allows you to prompt for input and store it in a variable. Read a line from the standard input and split it into fields.
Read command reads a single line from the standard input, or from file descriptor FD if the -u option is supplied. The line is split into fields as with word splitting, and the first word is assigned to the first NAME, the second word to the second NAME, and so on, with any leftover words assigned to the last NAME. Only the characters found in $IFS are recognized as word delimiters.
shell allows to prompt for user input.
Syntax:
read [-ers] [-a array] [-d delim] [-i text] [-n nchars] [-N nchars] [-p prompt] [-t timeout] [-u fd] [name ...]

• words entered by user are assigned to varname and “more vars”
• last variable gets rest of input line

 

USER INPUT EXAMPLE

#! /bin/bash

echo "Enter name : "
read name
echo "Enterd name : $name"

# Multiple inputs
echo "Enter names : "
read name1 name2 name3
echo "Names : $name1 , $name2, $name3"

# Two commonly used options however are 
# -p which allows you to specify a prompt
# -s which makes the input silent.
read -p 'username : ' user_var
read -sp 'password : ' pass_var
echo
echo "username : $user_var"
echo "password : $pass_var"

# -a makes read command to read into an array
echo "Enter name : "
read -a names
echo "Names : ${names[0]}, ${names[1]}"

# read command will now store the reply into the default build-in variable $REPLY
echo "Enter name : "
read 
echo "Name : $REPLY"

Output of the above script:

test@test$ ./hello.sh 
Enter name : 
Mark
Enterd name : Mark
Enter names : 
Mark Tom John
Names : Mark , Tom, John
username : my_user
password : 
username : my_user
password : 12345
Enter name : 
Mark Tom 
Names : Mark, Tom
Enter name : 
Mark

 

OPTIONS:

-a array	assign the words read to sequential indices of the array variable ARRAY, starting at zero
-d delim	continue until the first character of DELIM is read, rather than newline
-e	use Readline to obtain the line in an interactive shell
-i text	Use TEXT as the initial text for Readline
-n nchars	return after reading NCHARS characters rather than waiting for a newline, but honor a delimiter if fewer than NCHARS characters are read before the delimiter
-N nchars	return only after reading exactly NCHARS characters, unless EOF is encountered or read times out, ignoring any delimiter
-p prompt	output the string PROMPT without a trailing newline before attempting to read
-r	do not allow backslashes to escape any characters
-s	do not echo input coming from a terminal
-u fd	read from file descriptor FD instead of the standard input
-t timeout	time out and return failure if a complete line of input is not read withint TIMEOUT seconds. The value of the TMOUT variable is the default timeout. TIMEOUT may be a fractional number. If TIMEOUT is 0, read returns success only if input is available on the specified file descriptor. The exit status is greater than 128 if the timeout is exceeded