Variables from stdin - bash

Question

I want to get an input from the user using read
read line
and the proper input would be a string and then a number:
a 5
b 6
+ 87
How do you separate the "a" and 5 into two variables, with the 5 into a integer variable?

Answer 1

read supports the command line option -a, to store the input in an array like that:
$ read -a line
a 4
$ echo ${line[0]}
a
$ echo ${line[1]}
4
That would be nicer than using two variables, in my opinion.

Answer 2

I suggest reading the documenentation of read to get you started:
help read
Here are the first two paragraphs:
Read a line from the standard input and split it into fields.
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.
Note that bash doesn't have a notion of "integer variables" comparable to other programming languages. Bash variables are untyped. Declaring a variable as integer using declare -i only influences assignments to this variable -- everything that is not a valid integer is silently set to 0.

Answer 3

I presume you're operating in the shell since this post is tagged "bash" but you might want to make that explicit.
Anyway, the "read" command to the shell takes multiple variable names, not just one. You can give it two and it will hand each word on the line to you in the respective variables. (They're split on the field separator given by the IFS variable.)
The shell doesn't really have any distinction between "integer" variables and any other kind in the general case.
I suggest reading the man page for the shell fully if you really want to understand how to write shell scripts properly.

Answer 4

The read command will split your input along whatever is in $IFS. This, by default is whitespace, so simply doing this:
read my_string my_number
will split your input into two sections separated by the space. Sometimes, you'll see this:
read my_string my_number garbage
Because read will read in the entire rest of the line into the last variable no matter how many parameters you had. For example, if I had:
read my_string my_number
And the user put in:
this 1 foo foo foo!
$my_string will be this, but $my_number will be 1 foo foo foo!
By putting another variable (called garbage in this case), I eliminate this issue. If I put:
read my_string my_number garbage
And the user put in:
this 1 foo foo foo!
$my_string will be this, $my_number will be 1, and $garbage would be foo foo foo!.
A simple test program:
while read my_string my_number garbage
do
echo "The string is '$my_string'. The number is '$my_number'."
echo "Note there's no error checking of input."
echo "That's your job, Bunky."
done