Mac OS X Leopard - ARCAism

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CHAPTER 19 EXTENDING THE POWER OF DARWIN
The other common loop is the for loop. Rather than relying on a true/false condition like
the while and until loops, a for loop iterates over all the elements in a list. For example, a simple
script to echo back the command-line arguments could look like this:
#!/bin/sh
echo "The command line arguments given to $0 are: "
for x in $@
do
echo $x
done
NOTE $@ is a special variable that contains each command-line argument together in a single
variable.
You may find that there is situation where you need to get out of a loop before it completes,
which is accomplished with either the break or continue command. The break command will
immediately stop the current loop pass and exit the loop process entirely (that is, the script
will continue immediately following the loop). The continue command will cause a halt in the
current pass through the loop but will continue the loop process if the conditions are still met.
Input and Output
Many scripts you write will need to provide output, and often you may want a script to prompt
for input as well. In the previous chapter, you learned most of the basics you need in order to
output text either to the terminal or to a file using the echo command (with redirection if you
want to write the output to a file), but there is also the printf command that provides more
options in how your output is presented. To get information into a script, you can use the read
command, which will provide a prompt at the command line for input.
The following script (enhanced from previously) shows how read and printf work (line
numbers have been added for reference):
1: #!/bin/sh
2:
3: printf "Please enter your input here: "
4: read input
5: set $input
6: c=$#
7: printf "You entered The following: "
8: for x in $@
9: do
10: c=`expr $c - 1`
11: if [ $c -gt 0 ]
12: then
13: printf "\"$x\", "
14: else
15: printf "and \"$x\".\n"
16: fi
17: done
When you run this script, you get something along the lines of this:
Please enter your input here: hello goodbye dogcow
You entered The following: "hello", "goodbye", and "dogcow".