handy makefile script

I frequently find myself looking for default make rules, and inevitably how to print their values.  Here's a script to help.

Adapted from https://blog.melski.net/2010/11/30/makefile-hacks-print-the-value-of-any-variable/

$ cat ~/bin/make-vars 
#!/bin/bash

_vars=
for v in $@; do
  _vars="${_vars} print-${v}"
done

make -f- ${_vars} <<'EOF'
print-%:
	@echo '$*=$($*)'
	@echo '  origin = $(origin $*)'
	@echo '  flavor = $(flavor $*)'
	@echo '   value = $(value  $*)'
EOF

Here it is in use

$ make-vars LINK.cc
LINK.cc=c++    
  origin = default
  flavor = recursive
   value = $(CXX) $(CXXFLAGS) $(CPPFLAGS) $(LDFLAGS) $(TARGET_ARCH)

apache zookeeper status with bash

Most Apache ZooKeeper users are familiar with ZooKeeper's four letter words. And many bash users know that recent versions of the popular shell can redirect to network ports. But I've yet to see the two used together. The other day I found myself without netcat and looking for a quick way to get stats out of ZooKeeper. A short bash function later and I can easily check on ZooKeeper from any shell (so much quicker than spinning up a JVM).

zk4 () 
{ 
    echo "${2-localhost}:${3-2181}> ${1-ruok}"
    exec 3<> /dev/tcp/${2-localhost}/${3-2181}
    echo ${1-ruok} 1>&3
    cat 0<&3
    [[ ${1-ruok} == "ruok" ]] && echo
}

Usage is simple, by default it will issue the ruok command to localhost on the default port 2181. But you can specify alternate values for each of the host, port, and command parameters.

zk4 stat
zk4 srvr
zk4 ruok zk-server1.myco.com 20181