Year: 2009

PHP

Running a PHP Script as Daemon

Post author By masnun
Post date November 2, 2009
6 Comments on Running a PHP Script as Daemon

For our ongoing project at Leevio, I had to find a way to run a php script as a daemon. I checked out a few techniques. I didn’t like any of them much. I needed a way to run the intended script and then exit the terminal leaving the script to keep running in the background.

After a bit of hard work, I chose to use the PCNTL functions to achieve my goal. Here’s the code I used:

<?php
declare(ticks=1);

$pid = pcntl_fork();
if ($pid == -1) {
    die("could not fork");
} else if ($pid) {
        exit(); // it's the parent -- lets quit
    } else {
    // it's the child -- nothing to do at the moment
    }

// detatch from the terminal
if (posix_setsid() == -1) {
    die("could not detach from terminal");
}

// setup signal handlers
pcntl_signal(SIGTERM, "sig_handler");
pcntl_signal(SIGHUP, "sig_handler");

// launch the script -- transfer the args to the child script
shell_exec("php script.php {$argv[1]} {$argv[2]} {$argv[3]} ");

function sig_handler($signo) {

    switch ($signo) {
        case SIGTERM:
        // handle shutdown tasks
            exit;
            break;
        case SIGHUP:
        // handle restart tasks
            break;
        default:
    // handle all other signals
    }

}

?>

<?php

declare(ticks=1);

$pid = pcntl_fork();

if ($pid == -1) {

die("could not fork");

} else if ($pid) {

exit(); // it's the parent -- lets quit

} else {

// it's the child -- nothing to do at the moment

}

// detatch from the terminal

if (posix_setsid() == -1) {

die("could not detach from terminal");

}

// setup signal handlers

pcntl_signal(SIGTERM, "sig_handler");

pcntl_signal(SIGHUP, "sig_handler");

// launch the script -- transfer the args to the child script

shell_exec("php script.php {$argv[1]} {$argv[2]} {$argv[3]} ");

function sig_handler($signo) {

switch ($signo) {

case SIGTERM:

// handle shutdown tasks

exit;

break;

case SIGHUP:

// handle restart tasks

break;

default:

// handle all other signals

}

Note that, in this case, the daemon quits the moment the shell_exec() command is executed. We are executing our intended PHP script as a sub process which has been detached from the terminal. The script has a while loop to keep it running forever. So, we can safely quit the main process while the forked process remains alive with the php script being executed 😀

Python

Python: Printing without newline or space :)

Post author By masnun
Post date November 2, 2009
3 Comments on Python: Printing without newline or space :)

While coding in Python, I have seen that the Print statement adds a newline to it’s output which is very helpful in most cases. While I have to add a newline character manually in PHP, I have to type less in Python. I used to love this feature until I faced a situation when I have to print out data without any newline character or space. I finally found out the solution 🙂 I have to write the characters of a string manually to stdout using the “sys” module.

Have a look at the following codes:

import sys

def masnun_print(string):
	for c in str(string):
		sys.stdout.write(c)


masnun_print("Hello world!")

masnun_print("\n")

for x in range(100):
	masnun_print(x)

masnun_print("\n")

import sys

def masnun_print(string):

for c in str(string):

sys.stdout.write(c)

masnun_print("Hello world!")

masnun_print("\n")

for x in range(100):

masnun_print(x)

masnun_print("\n")

As you can see, I have defined a function masnun_print() that prints out it’s default argument without space just like the echo statement in PHP. To give a line break between the “Hello World!” and the “1 to 100 series”, we have manually printed out newline character 🙂

PHP Python

Handling Exceptions in PHP and Python

Post author By masnun
Post date November 2, 2009
1 Comment on Handling Exceptions in PHP and Python

It’s really a very important programming practice to properly handle any possible exceptions… It makes the code more stable, efficient and re-usable.

PHP:
PHP now has a very good exception handling mechanism. Just put a “try” block and then “catch ” the exception if anything goes wrong 🙂

Have a look at the following code:

<?php
function masnun() {
    throw new Exception("Damn!"); }

try {
    masnun();
}
catch (Exception $e) { echo "Exception: ".$e->getMessage()."\n"; }
?>

<?php

function masnun() {

throw new Exception("Damn!"); }

try {

masnun();

}

catch (Exception $e) { echo "Exception: ".$e->getMessage()."\n"; }

The code is self explanatory. But you must use the “Exception” word before $e in the catch block to get things going perfectly. Like I did, you can “throw” a new exception in case there was really something unexpected in your code 🙂

Python:
Python is just a fantastic language. Here’s the Python equivalent of the above code snippet:

#!/usr/bin/env python

def masnun():
	raise Exception("Damn!")

try:
	masnun()

except Exception as e:
	print "Exception:", e

#!/usr/bin/env python

def masnun():

raise Exception("Damn!")

try:

masnun()

except Exception as e:

print "Exception:", e

The only difference in PHP and Python’s exception handling is it’s language structure. In Python, we don’t throw an exception, rather we raise one. Just a bit of politeness! 😉

Conclusion:
Both PHP and Python has very good exception handling techniques. I can’t discuss them all on this blog but you should consult the respective manuals to master them. They are really very essential! 😀

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