#!/bin/sh

#   Yes, you can execute this whole script for demonstration.

#   Of course you also remember comments, the here document, and the :
#   command, right? :-)  Okay, so I effectively (but not literally)
#   comment out the part between the pairs of __EOT__ without having to
#   individually comment out most or all the lines in the section.

>>/dev/null 2>&1 : << \__EOT__

#   while syntax (until syntax is the same, just use until instead
#   of while, and the sense of the test is reversed):

while list

    # list remember definition of list, list can also be rather complex;
    # ----  return value of list determines if list within the loop runs

    #   need a newline or semicolon before do

do

    #   need whitespace (one or more blanks, tabs, and/or newlines)
    #   between do and list (so do can be recognized as keyword and not
    #   part of some other word)

    list

    #   need a newline or semicolon between list and done

done

__EOT__

# Typical fairly readable use in scripts:
n=1
while [ "$n" -le 3 ]
do
	echo "$n"
	n=`expr "$n" + 1`
done

# somewhat less readable version with minimum whitespace and no semicolons:
n=1
while [ "$n" -le 3 ]
do echo "$n"
n=`expr "$n" + 1`
done

# without newlines:
n=1; while [ "$n" -le 3 ]; do echo "$n"; n=`expr "$n" + 1`; done

# somewhat less readable version with minimum whitespace and no newlines
# within the command:
n=1;while [ "$n" -le 3 ];do echo "$n";n=`expr "$n" + 1`;done

#and an until example that does essentially the same thing;
#since until reverses the sense of the test, we likewise reversed the logic in
#the test itself so the result would be essentially the same:
n=1
until [ "$n" -gt 3 ]
do
	echo "$n"
	n=`expr "$n" + 1`
done