Apache configuration files

httpd.conf is Apache's main configuration file by default. It will then call out other files and directories via Include and IncludeOptional directives which is meant to simplify the main configuration file, and the structure wildly varies between platforms.

httpd.conf itself is located differently between platforms. These are some of the known locations;

Platform Location
xampp {installation directory}/apache/conf/httpd.conf
macOS /private/etc/apache2/httpd.conf
homebrew /usr/local/etc/apache2/2.4/httpd.conf
Debian/Ubuntu /etc/apache2/httpd.conf
RedHat/CentOS/Fedora /etc/httpd/conf/httpd.conf

If your platform of choice is not on the list, simply run httpd -V from the terminal and look for SERVER_CONFIG_FILE.

# httpd -V
Server version: Apache/2.4.25 (Unix)
Server built:   Feb  6 2017 20:02:10
Server's Module Magic Number: 20120211:67
Server loaded:  APR 1.5.2, APR-UTIL 1.5.4
Compiled using: APR 1.5.2, APR-UTIL 1.5.4
Architecture:   64-bit
Server MPM:     prefork
  threaded:     no
    forked:     yes (variable process count)
Server compiled with....
 -D APR_HAVE_IPV6 (IPv4-mapped addresses enabled)
 -D HTTPD_ROOT="/usr"
 -D SUEXEC_BIN="/usr/bin/suexec"
 -D DEFAULT_PIDLOG="/private/var/run/httpd.pid"
 -D DEFAULT_SCOREBOARD="logs/apache_runtime_status"
 -D DEFAULT_ERRORLOG="logs/error_log"
 -D AP_TYPES_CONFIG_FILE="/private/etc/apache2/mime.types"
 -D SERVER_CONFIG_FILE="/private/etc/apache2/httpd.conf"

Different platform might use different binary names such as apache, apache2, apachectl or apache2ctl

Use grep to get only the relevant line.

# httpd -V | grep SERVER_CONFIG_FILE
 -D SERVER_CONFIG_FILE="/private/etc/apache2/httpd.conf"

Combine the output for both HTTPD_ROOT and SERVER_CONFIG_FILE If the output doesn't provide absolute full path of the configuration file.