# If hello.c changes, this script needs to be
# re-run.
redo-ifchange hello.c

# Compile hello.c into the 'hello' binary.
#
# $3 is the redo variable that represents the
# output filename.  We want to build a file
# called "hello", but if we write that directly,
# then an interruption could result in a
# partially-written file.  Instead, write it to
# $3, and redo will move our output into its
# final location, only if this script completes
# successfully.
#
cc -o $3 hello.c -Wall