First cookbook example for the docs: Hello World in C.

Documentation/cookbook/hello/.gitignore

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+hello
+*~
+.*~

Documentation/cookbook/hello/all.do

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+redo-ifchange hello

Documentation/cookbook/hello/clean.do

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+rm -f hello *~ .*~

Documentation/cookbook/hello/hello.c

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+#include <stdio.h>
+
+int main() {
+    printf("Hello, world!\n");
+    return 0;
+}

Documentation/cookbook/hello/hello.do

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+# 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

Documentation/cookbook/hello/test.do

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+# Make sure everything has been built before we start
+redo-ifchange all
+
+# Ensure that the hello program, when run, says
+# hello like we expect.
+if ./hello | grep -i 'hello' >/dev/null; then
+    echo "success" >&2
+    exit 0
+else
+    echo "missing 'hello' message!" >&2
+    exit 1
+fi