Makefile for program running on different machines

Question

Hi, I have a C++ program that will run on several machines that use a Network File System. For each of the C++ libraries that my program uses, I installed a version for each machine, under ~/program_files/machinename/libraryname.

"machinename" is obtained via bash command "hostname". On the machines I am using, "hostname" outputs something like "io21.aaa.bbb.edu" and I take only "io21" as "machinename" for the path to the libraries. In bash, I learned that

$ HOST=hostname # now the value of HOST is "io21.aaa.bbb.edu"

$ HOST=${HOST%%.*} # extract "io21" from "io21.aaa.bbb.edu"

$ echo ${HOST}

io21

In the Makefile of my program, I want to call these bash commands to specify the path to the library according to the current machine:

HOST := $(shell hostname)

HOST := $(shell ${HOST%%.*})

LDFLAGS=-L${HOME}/program_files/${HOST}/libraryname/lib

CXXFLAGS=-Wall -I${HOME}/program_files/${HOST}/libraryname/include

The first line is working i.e. HOST is "io21.aaa.bbb.edu", but the second line which extracts "io21" doesn't work and HOST is still "io21.aaa.bbb.edu".

I am wondering how I should solve this problem?

Thanks and regards!

Answer 1

Alternatively you can use

HOST := $(shell echo $(HOST) | cut -d . -f 1)

Answer 2

Give this a try:

SHELL = /bin/bash
HOST := $(shell hostname)
HOST := $(shell host=$(HOST);echo $${host%%.*})

make defaults to /bin/sh which may not support the $(var%%string) construct depending on which version you have. Also, mixing make variables and bash variables is a bit challenging.