CMake get HOSTNAME environment variable

Question

I have both HOSTNAME and USER defined as environment variables (Linux Ubuntu)

echo $USER
pvicente
echo $HOSTNAME
glace

I get the variables in CMakeLists.txt using

message("-- USER environment variable is set to: " $ENV{USER})
message("-- HOSTNAME environment variable is set to: " $ENV{HOSTNAME})

but USER is detected and not HOSTNAME

output is

-- USER environment variable is set to: pvicente
-- HOSTNAME environment variable is set to:

Answer 1

You could check which environment variables CMake does see with

$ cmake -E environment

It gives my hostname in an environment variable named NAME. So try:

message("-- USER environment variable is set to: " $ENV{USER})
message("-- HOSTNAME environment variable is set to: " $ENV{NAME})

But the official cross-platform CMake way is:

cmake_host_system_information(RESULT _host_name QUERY HOSTNAME)
message("-- _host_name variable is set to: " ${_host_name})

Reference

• cmake_host_system_information()

Answer 2

NOTE: I don't work with cmake so I did a bit of googling and came up with the following ... a bit more than I could fit into a comment ...

According to the first post @ this link:

• sh -c echo \$HOSTNAME => ...nothing... ; HOSTNAME is not (automatically) set under the sh shell
• bash -c echo \$HOSTNAME => glace ; HOSTNAME is (automatically) set under the bash shell
• cmake runs commands under the sh shell, so HOSTNAME will not be available to cmake

At the bottom of that same link there's a recommendation to use the site_name() function ...

SITE_NAME(mySite)             => obtain hostname and place in variable 'mySite'
MESSAGE(mySite='${mySite}')

... which appears to jive with the (sparse) documentation (site_name() documentation)