I was wondering if it would be possible to add to FindCURL.cmake the ability to return CURL_EXECUTABLE much like FindWget.cmake returns WGET_EXECUTABLE.
I found myself recently having to figure out how to detect if I am on an AWS EC2 system. As the preferred method is to query a URL, I wrote something like:
find_package(CURL)
if (CURL_FOUND)
execute_process(
COMMAND curl --connect-timeout 0.1 http://169.254.169.254/latest/meta-data/instance-id
TIMEOUT 1.0
OUTPUT_QUIET ERROR_QUIET
RESULT_VARIABLE STATUS
)
if(STATUS AND NOT STATUS EQUAL 0)
set (DETECTED_SITE ${BUILD_SITE})
else ()
set (DETECTED_SITE "AWS")
endif ()
Not pretty, but it works. My only fear is that maybe (?) it is possible for CURL_FOUND to be true but curl not be in the PATH? Maybe not, but using ${CURL_EXECUTABLE} seems more “right” to me.
(Note: The URL is a bit different because the AWS Guru where I work says he uses that. I follow his lead. )
At the moment, FindCURL does not search for the curl executable. This could be searched for, and provide both a variable and an imported target.
However, there’s an easier way in your case. CMake includes file download capabilities through the file(DOWNLOAD) command (it even uses libcurl under the hood!)
@kyle.edwards Hmm. Interesting. I guess I can give that a try. I mainly went with “call curl directly” because I know looking for that URL on a non-AWS system can “lock up” as it retries. But file(DOWNLOAD) does provide TIMEOUTand INACTIVITY_TIMEOUT…
One question: what happens if you are on a system without cURL? Does it fall over to wget?
file(DOWNLOAD http://169.254.169.254/latest/meta-data/instance-id instance-id
INACTIVITY_TIMEOUT 1.0
TIMEOUT 1.0
STATUS DOWNLOAD_STATUS
)
list(GET DOWNLOAD_STATUS 0 RETURN_CODE)
if (RETURN_CODE EQUAL 0)
set (DETECTED_SITE "AWS")
else ()
set (DETECTED_SITE ${BUILD_SITE})
endif ()
which seems to work. I’m debating whether I should file(REMOVE) the output. It’s 19 bytes if it exists and I wonder if some day it’ll be useful…
)