When enabling Web Sharing on Mac OS X (10.6 Snow Leopard and later), Apache logs aren't stored in the typical Linux location of /var/log/httpd. Apple's implementation uses different paths:

# Default Apache log locations for Mac OS X Web Sharing:
/private/var/log/apache2/access_log
/private/var/log/apache2/error_log

To view the logs in real-time:

# View access logs with user agent strings
tail -f /private/var/log/apache2/access_log

# Filter for specific user agents
grep -i "iPhone" /private/var/log/apache2/access_log

You might need sudo privileges to access these files. For GUI access:

open /private/var/log/apache2/

Or use the Finder 'Go to Folder' feature (⌘+Shift+G) and enter the path.

Edit /private/etc/apache2/httpd.conf to modify the log format:

# Example custom log format including full user agent
LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" combined

OS X may rotate logs automatically. Check for compressed archives:

ls /private/var/log/apache2/access_log*

When Web Sharing is enabled via System Preferences > Sharing on Mac OS X 10.6 (Snow Leopard), Apache stores its logs in a different location than typical Linux installations. The default paths are:

/private/var/log/apache2/access_log
/private/var/log/apache2/error_log

Since these files reside in a protected system directory, you'll need to use Terminal with sudo privileges:

sudo ls -la /private/var/log/apache2/
sudo tail -f /private/var/log/apache2/access_log

To verify if custom logging locations are defined, inspect the Apache configuration:

sudo nano /private/etc/apache2/httpd.conf

Look for these directives:

ErrorLog "/private/var/log/apache2/error_log"
CustomLog "/private/var/log/apache2/access_log" common

To specifically extract user agent information, you can use command-line tools:

awk -F\" '{print $6}' /private/var/log/apache2/access_log | sort | uniq -c | sort -rn

Or create a PHP script to process logs:

<?php
$logFile = '/private/var/log/apache2/access_log';
$lines = file($logFile);
$agents = array();

foreach ($lines as $line) {
    if (preg_match('/\"(.*?)\"/', $line, $matches)) {
        $agents[] = $matches[1];
    }
}

print_r(array_count_values($agents));
?>

To enhance logging for better user agent analysis, modify your httpd.conf:

LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" combined
CustomLog "/private/var/log/apache2/access_log" combined

Mac OS X uses newsyslog for log rotation. Configuration is found at:

/etc/newsyslog.conf

Example entry for Apache logs:

/private/var/log/apache2/access_log   644  7     *    @T00  J
/private/var/log/apache2/error_log    644  7     *    @T00  J