III. RESULTADOS
3.3. Análisis inferencial
Introduction to the PHP Command-Line Interface (CLI)
If you built PHP with --enable-cli, a binary called phpis installed into the binaries directory of the installation path. By default this is /usr/local/bin.To prevent having to specify the full path of phpevery time you run it, this directory should be in your
PATHenvironment variable.To execute a PHP script phpscript.phpfrom the command line on a Unix system, you can type this:
> php phpscript.php
Alternatively, you can add the following line to the top of your script:
#!/usr/bin/env php
and then mark the script as executable with chmod, as follows:
> chmod u+rx phpscript.php
Now you can run phpscript.phpas follows:
> ./phpscript.php
This#!syntax is known as a “she-bang,” and using it is the standard way of making script executables on Unix systems.
On Windows systems, your registry will be modified to associate .phpscripts with thephpexecutable so that when you click on them, they will be parsed and run.
However, because PHP has a wider deployment on Unix systems (mainly for security, cost, and performance reasons) than on Windows systems, this book uses Unix examples exclusively.
Except for the way they handle input, PHP command-line scripts behave very much like their Web-based brethren.
Handling Input/Output (I/O)
A central aspect of the Unix design philosophy is that a number of small and independ-ent programs can be chained together to perform complicated tasks.This chaining is tra-ditionally accomplished by having a program read input from the terminal and send its output back to the terminal.The Unix environment provides three special file handles that can be used to send and receive data between an application and the invoking user’s terminal (also known as a tty):
n stdin—Pronounced “standard in” or “standard input,” standard input captures any data that is input through the terminal.
n stdout—Pronounced “standard out” or “standard output,” standard output goes directly to your screen (and if you are redirecting the output to another program, it is received on its stdin).When you use printorechoin the PHP CGI or CLI, the data is sent to stdout.
n stderr—Pronounced “standard error,” this is also directed to the user’s terminal, but over a different file handle than stdin.stderrgenerated by a program will not be read into another application’s stdinfile handle without the use of output redirection. (See the man page for your terminal shell to see how to do this; it’s different for each one.)
In the PHP CLI, the special file handles can be accessed by using the following con-stants:
n STDIN
n STDOUT
n STDERR
Using these constants is identical to opening the streams manually. (If you are running the PHP CGI version, you need to do this manually.) You explicitly open those streams as follows:
$stdin = fopen(“php://stdin”, “r”);
$stdout = fopen(“php://stdout”, “w”);
$stderr = fopen(“php://stderr”, “w”);
Why Use STDOUT?
Although it might seem pointless to use STDOUT as a file handle when you can directly print by using print/echo, it is actually quite convenient. STDOUT allows you to write output functions that simply take stream resources, so that you can easily switch between sending your output to the user’s terminal, to a remote server via an HTTP stream, or to anywhere via any other output stream.
The downside is that you cannot take advantage of PHP’s output filters or output buffering, but you can register your own streams filters via streams_filter_register().
Here is a quick script that reads in a file on stdin, numbers each line, and outputs the result to stdout:
#!/usr/bin/env php
<?php
$lineno = 1;
while(($line = fgets(STDIN)) != false) { fputs(STDOUT, “$lineno $line”);
$lineno++;
}
?>
127 Handling Input/Output (I/O)
When you run this script on itself, you get the following output:
1 #!/usr/bin/env php 2 <?php
3
4 $lineno = 1;
5 while(($line = fgets(STDIN)) != false) { 6 fputs(STDOUT, “$lineno $line”);
7 $lineno++;
8 } 9 ?>
stderris convenient to use for error notifications and debugging because it will not be read in by a receiving program’s stdin.The following is a program that reads in an Apache combined-format log and reports on the number of unique IP addresses and browser types seen in the file:
<?php
$counts = array(‘ip’ => array(), ‘user_agent’ => array());
while(($line = fgets(STDIN)) != false) {
# This regex matches a combined log format line field-by-field.
$regex = ‘/^(\S+) (\S+) (\S+) \[([^:]+):(\d+:\d+:\d+) ([^\]]+)\] ‘.
‘“(\S+) (.*?) (\S+)” (\S+) (\S+) “([^”]*)” “([^”]*)”$/’; preg_match($regex,$line,$matches);
list(, $ip, $ident_name, $remote_user, $date, $time,
$gmt_off, $method, $url, $protocol, $code,
$bytes, $referrer, $user_agent) = $matches;
$counts[‘ip’][“$ip”]++;
$counts[‘user_agent’][“$user_agent”]++;
# Print a ‘.’ to STDERR every thousand lines processed.
if(($lineno++ % 1000) == 0) { fwrite(STDERR, “.”);
} }
arsort($counts[‘ip’], SORT_NUMERIC);
reset($counts[‘ip’]);
arsort($counts[‘user_agent’], SORT_NUMERIC);
reset($counts[‘user_agent’]);
foreach(array(‘ip’, ‘user_agent’) as $field) {
$i = 0;
print “Top number of requests by $field\n”; print “---\n”; foreach($counts[$field] as $k => $v) {
print “$v\t\t$k\n”;
if($i++ == 10) { break;
} }
print “\n\n”; }
?>
The script works by reading in a logfile on STDINand matching each line against $regex to extract individual fields.The script then computes summary statistics, counting the number of requests per unique IP address and per unique Web server user agent. Because combined-format logfiles are large, you can output a .tostderrevery 1,000 lines to reflect the parsing progress. If the output of the script is redirected to a file, the end report will appear in the file, but the .’s will only appear on the user’s screen.