# In this script, we will demonstrate how commands can be chained.
# This is sometimes useful in ‹if› conditions, but also in other
# scenarios. We already know pipes: those are a form of chaining
# too. But we are now interested in simpler things. You know that if
# you enter two commands on separate lines (in a script, or in an
# interactive session), those commands will run in a sequence. A
# semicolon does the same thing:

echo foo ; echo bar

# That is not very interesting, but sometimes useful, if you want to
# run a sequence of commands at once and each of them takes a while
# and you don't want to watch for each to finish so you can type in
# the next one.

# The next two ways are more interesting: the ‹&&› and ‹||› operators:

true  && echo "this command will run"
false && echo "this command will not run"

# Just like in C, && is short-circuiting: if the first command
# fails, the result must always be false and running the second
# command is not needed.  Same (but opposite) with ‹||›:

true  || echo "this command will not run"
false || echo "this command will run"

# We can form a longer chain, too:

true  && echo "this will run"  || echo "but this won't"
false && echo "this won't run" || echo "but this will"

# Of course, you can use those operators in conditionals:

if true && false; then echo "not happening"; fi

if test -f file.txt && test -f file.bak; then
    echo "both file.txt and file.bak exist and are regular files"
fi

# This is all I wanted to say about chaining for now. We might look
# at the ‹&› operator later in the semester, if there's enough time.
# For now, let's move on to loops:
#
#     $ micro loops.sh