6. <Directory> and </Directory>

<Directory> and </Directory> are used to enclose a group of directives that will apply only to the named directory and sub-directories of that directory. Any directive that is allowed in a directory context may be used. Directory-path is either the full path to a directory, or a wild-card string using Unix shell-style matching. In a wild-card string, ? matches any single character, and * matches any sequences of characters. You may also use [] character ranges. None of the wildcards match a `/' character, so <Directory /*/public_html> will not match /home/user/public_html, but <Directory /home/*/public_html> will match.

Example1:

Example2:

Extended regular expressions can also be used, with the addition of the ~ character.

would match directories in /www/ that consisted of three numbers.

Example3:

Note that the default Apache access for <Directory /> is Allow from All. This means that Apache will serve any file mapped from an URL. It is recommended that you change this with a block such as

and then override this for directories you want accessible. See the Security Tips page for more details.

7. error log - ErrorLog directive and LogLevel directive

The server error log, whose name and location is set by the ErrorLog directive, is the most important log file. This is the place where Apache httpd will send diagnostic information and record any errors that it encounters in processing requests. It is the first place to look when a problem occurs with starting the server or with the operation of the server, since it will often contain details of what went wrong and how to fix it.

The error log is usually written to a file (typically error_log on unix systems and error.log on Windows and OS/2).

The format of the error log is relatively free-form and descriptive. But there is certain information that is contained in most error log entries.

Example:

The first item in the log entry is the date and time of the message.

The second entry lists the severity of the error being reported. The LogLevel directive is used to control the types of errors that are sent to the error log by restricting the severity level.

The third entry gives the IP address of the client that generated the error.

The fourth entry indicates that the server has been configured to deny the client access. The server reports the file-system path (as opposed to the web path) of the requested document.

During testing, it is often useful to continuously monitor the error log for any problems. On unix systems, you can accomplish this using:

8. access log - CustomLog directive and LogFormat directive

The server access log records all requests processed by the server. The location and content of the access log are controlled by the CustomLog directive. The LogFormat directive can be used to simplify the selection of the contents of the logs.

Of course, storing the information in the access log is only the start of log management. The next step is to analyze this information to produce useful statistics. Log analysis in general is beyond the scope of this document. For more information about this topic, and for applications which perform log analysis, check the Open Directory or Yahoo.

The format of the access log is highly configurable. The format is specified using a format string that looks much like a C-style printf(1) format string. Some examples are presented in the next sections. For a complete list of the possible contents of the format string, see the mod_log_config format strings.

Common Log Format

1. directives的設定

A typical configuration for the access log might look as follows.

This defines the nickname common and associates it with a particular log format string. The format string consists of percent directives, each of which tell the server to log a particular piece of information. Literal characters may also be placed in the format string and will be copied directly into the log output. The quote character (") must be escaped by placing a back-slash before it to prevent it from being interpreted as the end of the format string. The format string may also contain the special control characters "\n" for new-line and "\t" for tab.

The CustomLog directive sets up a new log file using the defined nickname. The filename for the access log is relative to the ServerRoot unless it begins with a slash.

2. 檢視log的內容

The above configuration will write log entries in a format known as the Common Log Format (CLF). This standard format can be produced by many different web servers and read by many log analysis programs. The log file entries produced in CLF will look something like this:

Each part of this log entry is described below.

127.0.0.1 (%h)

This is the IP address of the client (remote host) which made the request to the server. The IP address reported here is not necessarily the address of the machine at which the user is sitting. If a proxy server exists between the user and the server, this address will be the address of the proxy, rather than the originating machine.

- (%l)

The "hyphen" in the output indicates that the requested piece of information is not available. In this case, the information  is the RFC 1413 identity of the client determined by identd on the clients machine. This information is highly unreliable and should almost never be used except on tightly controlled internal networks. Apache httpd will not even attempt to determine this information unless IdentityCheck is set to On.

frank (%u)

This is the userid of the person requesting the document as determined by HTTP authentication. The same value is typically provided to CGI scripts in the REMOTE_USER environment variable. If the status code for the request (see below) is 401, then this value should not be trusted because the user is not yet authenticated. If the document is not password protected, this entry will be "-" just like the previous one.

[10/Oct/2000:13:55:36 -0700] (%t)

The time that the server finished processing the request. The format is:

[day/month/year:hour:minute:second zone]
day = 2*digit
month = 3*letter
year = 4*digit
hour = 2*digit
minute = 2*digit
second = 2*digit
zone = (`+' | `-') 4*digit

It is possible to have the time displayed in another format by specifying %{format}t in the log format string, where format is as in strftime(3) from the C standard library.

"GET /apache_pb.gif HTTP/1.0" (\"%r\")

The request line from the client is given in double quotes. The request line contains a great deal of useful information. First, the method used by the client is GET. Second, the client requested the resource /apache_pb.gif, and third, the client used the protocol HTTP/1.0. It is also possible to log one or more parts of the request line independently. For example, the format string "%m %U%q %H" will log the method, path, query-string, and protocol, resulting in exactly the same output as "%r".

200 (%>s)

This is the status code that the server sends back to the client. This information is very valuable, because it reveals whether the request resulted in a successful response (codes beginning in 2), a redirection (codes beginning in 3), an error caused by the client (codes beginning in 4), or an error in the server (codes beginning in 5). The full list of possible status codes can be found in the HTTP specification (RFC2616 section 10).

2326 (%b)

The last entry indicates the size of the object returned to the client, not including the response headers. If no content was returned to the client, this value will be "-". To log "0" for no content, use %B instead.