无法通过perl File :: Tail读取文件

Question

i am trying to get realtime tail of a nginx log file using perl CGI. i have given permission to file is 644. my perl cgi code is as follows:

#!/usr/bin/perl
use CGI;
use File::Tail;

print "Content-type: text/html\n\n";

$| = 1; #set auto flush on

# param for specifying number of lines to tail.
#$n =  CGI::param('n');
$n = '20';
$file_name = "/var/log/nginx/access.log";

#show 100 lines by default
$tail = $n?$n:100;

# specifying default as of now
$file_name = $file_name?$file_name:"$file_name";

# tail -n <tail_lines>. Start with tail_lines
$tail_lines=10;

$tail_file=File::Tail->new(name=>$file_name,
                            maxinterval=>2,
                            adjustafter=>1,
                            maxbuf=>16384,
                            tail=>$tail_lines);


while (defined($readline=$tail_file->read))
{
    print $readline."</br>";
}

i have given permission to as follows

-rw-r--r--. 1 nginx nginx 32565 Jan 7 17:17 /var/log/nginx/access.log

and i am facing this problem with tailf only..............

permission related in nginx log

[Tue Jan 07 17:16:07 2014] [error] [client 127.0.0.1] Error opening /var/log/nginx/access.log: Permission denied at /var/www/cgi-bin/clarity.pl line 32, referer: http://host:8888/clarity.html

help me out from this problem...?

Answer 1

Have you set something up such that the perl CGI script runs as a separate user?

Typically most modern nginx installations have scripts executing as a different user. This way if someone hacks into your CGI script, they cannot easily affect the actual web server process.

You can try something like

print "real uid: $<, effective uid: $>\n";

in a separate CGI script to test what user your script is actually running as.