How to Fix Nagios Plugin check_http.c Error ssl_version Undeclared

Question: I’m installing Nagios plugin 1.4.16, when I execute make, I get “check_http.c:312: error: ssl_version undeclared” error message. How can I fix this?

Answer: After you downloaded the nagios-plugins-1.4.16.tar.gz file, you’ll first do ./configure as shown below.

# ./configure --with-nagios-user=nagios --with-nagios-group=nagios

Next, when you execute make command, you’ll get the following ssl_version error message as shown below.

# make
check_http.c: In function process_arguments:
check_http.c:312: error: ssl_versionâ undeclared (first use in this function)
check_http.c:312: error: (Each undeclared identifier is reported only once
check_http.c:312: error: for each function it appears in.)
make[2]: *** [check_http.o] Error 1
make[2]: Leaving directory `/usr/save/nagios-plugins-1.4.16/plugins'
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory `/usr/save/nagios-plugins-1.4.16'
make: *** [all] Error 2

This is because you don’t have openssl-devel package on your system as shown below.

# rpm -qa | grep openssl
openssl-1.0.0-27.el6_4.2.x86_64

Install the openssl-devel using yum, or other package management utilities on your corresponding Linux distribution.

# yum install openssl-devel

Now, you’ll see both openssl and openssl-devel package.

# rpm -qa | grep openssl
openssl-devel-1.0.0-27.el6_4.2.x86_64
openssl-1.0.0-27.el6_4.2.x86_64

Note: If you try to do make again immediately, you’ll still get the same error message.

You should do the ./configure again, and then make, which will execute without any error message.

# ./configure --with-nagios-user=nagios --with-nagios-group=nagios

# make
...
...
make[2]: Leaving directory `/usr/save/nagios-plugins-1.4.16/plugins-root'
make[2]: Entering directory `/usr/save/nagios-plugins-1.4.16/po'
make[2]: Nothing to be done for `all'.
make[2]: Leaving directory `/usr/save/nagios-plugins-1.4.16/po'
make[2]: Entering directory `/usr/save/nagios-plugins-1.4.16'
make[2]: Leaving directory `/usr/save/nagios-plugins-1.4.16'
make[1]: Leaving directory `/usr/save/nagios-plugins-1.4.16'