TweetFollow Us on Twitter

Mac in The Shell: Scripting with PHP

Volume Number: 24 (2008)
Issue Number: 03
Column Tag: Mac in The Shell:

Mac in The Shell: Scripting with PHP

Forget that web stuff, PHP is a great scripting language!

by Edward Marczak

Introduction

Since the inception of this column, I've covered general shell tools, bash commands and general bash scripting. Life in the shell involves much more! There are many other scripting environments - and shells, for that matter! While I won't be stepping totally outside of bash, I will be looking at other ways to automate your environment. While I like bash, I don't necessarily love it. PHP - yes, the one you may know from web development - has a CLI component that makes a great scripting language. Of course, it's installed by default under OS X (version 5.2.4 as of OS 10.5.1). So let's dig in and learn some new techniques.

Why, oh Why?

Why am I forsaking bash? While bash is powerful, it falls down in some key areas, one of which being easy database access. Yes, using the tools we've talked about over the months, we could use the mysql binary, send output to standard out, grep-sed-and-awk our way to get what we're after. But that's not easy. Or elegant.

PHP is a dynamically and loosely typed language with extensions that allow easy access to data outside of its world. PHP supports access to raw network sockets, curl libraries allow access to URLs (ftp, http, https, etc.), and various database libraries allow access to various databases. This support needs to be compiled in, and Apple has made sure we have the tools we need. (You can look at everything that's compiled in by running php -r 'phpinfo();' | less. Once you're looking at that output, search for 'curl' and 'mysql').

PHP is also Open Source, like many of the packages that Apple includes with OS X. It was written by Rasmus Lerdorf in 1995 (as "PHP/FI" which evolved into the PHP we use today), and stands for "PHP: Hypertext Preprocessor". While its goal was for web development, it's also now nicely suited for scripting. (There wasn't always a CLI component).

What can PHP do? Just about anything! Well, anything that you'd use a scripting language for. PHP runs on just about every platform, and there is even a way to tie in a GUI (but that's beyond what I'm going to go into here. See http://gtk.php.net/ for more information).

Do the PHP

Nothing like an example to get things going. Most text editors recognize the .php filename extension and change modes accordingly. TextWrangler, BBEdit, vi and TextMate all have colorizations and in some cases, extra support for the PHP language and its constructs. So, fire up your favorite one, and type the venerable "hello world" program:

Listing 1: hello_world.php

#!/usr/bin/php
<?php
print "Hello, world!\n";
?>

As with all programs that we're going to run from the shell, we need to mark it executable if we intend to run it by name alone (chmod 770 hello_world.php). Notice that I used the shebang line here (line 1). Technically, you could omit that, and run the program like this:

php hello_world.php

However, I think the shebang line along with marking it executable underscores that we can treat PHP like a 'real' scripting language. This way, we can simply:

./hello_world.php

and be on our way. Let's look closer at listing 1.

First, we have the shebang line as discussed. Next, we have this odd-looking construct: "<?php". This simply signifies that what follows will be PHP code. As originally intended, PHP can be embedded in HTML documents. The PHP opening ("<?php") and closing ("?>") tags allow you to jump in and out of "PHP mode." (As an aside, if you're not in "PHP mode," you're in HTML mode, and the php engine will happily spit stray lines back to stdout. That's why there is no blank line in listing 1 between the shebang and the php opening tag. Also, the final closing tag, technically, is optional).

The next line contains a print statement, which simply outputs its arguments to standard out. In this case, the argument is the string "Hello, world!\n". The "\n" character is a newline, which print does not output on its own after printing.

Finally, we close with an ending php tag: "?>". All in all, you probably figured out this short program without explanation. One thing to note, though: unlike the bash constructs that we've seen, PHP expects each line to end with a semi-colon (";"). PHP uses this as a line separator, and the PHP engine will print errors if you omit it at the end of any line or between any separate statements.

Beyond The Beginning

Like any good programming environment, PHP supports comments, variables and all basic constructs such as flow control statements and loops. Let's get the easy one out of the way: good code is commented code.

PHP honors C, C++ and Perl style comments. Let's look at all three in action.

Listing 2: Comment example

<?php
/* example1.php
This short code snippet illustrates good code commenting.
Ed Marczak, 2008
*/
$numargs = func_num_args();      // This retrieves the number of args passed
echo "Number of arguments: $numargs\n";
# Here's the closing tag:
?>

I'm sure I don't need to belabor that any further.

Variables in PHP are represented by a dollar sign followed by the name of the variable. The variable name is case-sensitive. A valid variable name starts with a letter or underscore (not a number) and is then followed by any number of letters, numbers or underscores. (With one exception: "$this" is a reserved variable name and cannot be overridden). As mentioned, PHP is both loosely and dynamically typed. This is a fancy way of saying variables take on the properties of the contents assigned to them, and generally 'do the right thing.' As always, an example:

Listing 3: PHP Variable Demo

<?php
$a = "apple";   // a is a string
if ($a=="orange") print "Orange\n";
$a=5      // a is now an integer
?>

(Note: the final closing tag can also act as a semi-colon, hence its omission in listing 3). In general, this aids the rapid development that can be done with PHP. However, if you ever do need to find out what type a variable is at the moment, you have several options. You can print it out using getype() or you can test for it with istype(). You can also use "===" in comparisons to ensure not only that variable contents are the same, but that types match also. You can force a variable to be a certain type by using settype(), or by casting the variable if you're familiar with that from other languages. I won't delve into this much deeper except to say to be careful with this. Again, the PHP engine will try to 'do the right thing.' Take listing 4 as your warning.

Listing 4: Casting example

<?php
$x=TRUE;   // x is a boolean
$x=(string)$x;   // x now contains "1"
$x="9bar";   // string again
settype($x, integer);   // x is now an int, and 0
?>

In a final show of the PHP engine trying to do the right thing, it will "juggle types" as needed. So, if $a is an integer and $b is a float, adding them together evaluates everything as a float, and returns a float. Strings also gain an implicit conversion if used with mathematical operators. "15" + 5 equals integer 20.

Speaking of types, PHP supports the following types:

  • Integer

  • Boolean

  • Float (aka "double" or "real")

  • String

  • Binary

  • Array

  • Object

We'll be exploring these types as we go.

Second Gear

Other things to note about how PHP deals with string variables and quoting. String literals can be specified as single quoted, double quoted or use heredoc syntax. I'll concentrate on the first two for now.

With single quotes, variables are not expanded, and only a backslash need be escaped. You can nest double quotes within single quotes. For example:

print 'Monty Python\'s Flying Circus.';
print 'I like $dollars';
print 'I\'m splitting
      this line';

The first line prints "Monty Python's Flying Circus." The second literally prints "I like $dollars." - without trying to evaluate "$dollars" as a variable. The third example shows that we can even embed the newline character into a single-quoted string.

If a string is enclosed in double quotes, PHP expands variables and interprets certain escape sequences. The major ones are:

  • \n linefeed (0x0A, or 10 in ASCII)

  • \r Carriage return (0x0D, or 13 in ASCII)

  • \t Horizontal tab (HT or 0x09 (9) in ASCII)

  • \v Vertical tab

  • \f Form feed (since PHP 5.2.5)

  • \\ Backslash

  • \$ Dollar sign

  • \" Double quote

In action:

$num_dogs=6;
print "There are $num_dogs dogs\n";

This prints "There are 6 dogs" followed by a newline character.

Flow Control

All flow control deals with comparison for purposes of directing flow or knowing how many times to loop. PHP understands the following flow control comparison operators:

  • == Equal

  • === Identical

  • != Not equal

  • <> Not equal

  • !== Not identical

  • < Less than

  • > Greater than

  • <= Less than or equal to

  • >= Greater than or equal to

Let's use these in a simple example:

Listing 5: Basic Flow Control

if ($a > $b) {
   print "a is greater than b\n";
   $top = $a;
} else {
   print "b is greater than a";
   $top = $b;
}

PHP uses curly brace syntax to create a statement group. Listing 5 illustrates an if flow control structure. Generically, if tests an expression - any expression. If a is greater than b, the flow follows into the first group if statements. Otherwise, we run the statements in the else group.

Control structures can also be nested.

Listing 6: Nested control structures

$i=100;
while ($i<=500) {
   if (fmod($i,2)==0)
      print "$i\n";
   $i++;
}

You may note from listing 6 that if a control structure only has a single statement, curly braces can be omitted (though I recommend always retaining the braces).

Shell Interaction

There are a few ways that you can have your PHP script interact with the shell in general. First, you can have PHP execute other shell commands. Second, you can pass arguments in to the script from the command line. Third, PHP is fully capable of reading from standard in and directing output to standard out and standard error.

The first one is pretty easy: to run a shell command - one that may have no built-in PHP equivalent - you simply use the backtick operator. The output of the shell command is assigned to the variable of your choice. Listing 7 shows this in action.

Listing 7: diskmon.php

#!/usr/bin/php
<?php
$freespace=trim(`df / | tail -1 | awk '{print $5}' | cut -d "%" -f1`);
if ($freespace > 80) {
   print "System volume is at ${freespace}% full - you may want to look at that.\n";
   die();
}
if ($freespace > 50) {
   print "System volume is at ${freespace}% full - seems OK.\n";
   die();
}
if ($freespace >= 0) {
   print "System volume is only ${freespace}% full - no problems.\n";
   die();
}
print "System volume is an indeterminate amount full.\n";

Accepting and handling command line arguments is also a straight-forward venture. PHP populates the variables $argc and $argv (an array) with the count of arguments and the contents of the arguments respectively. A simple example:

if ($argc < 3) {   // we need 2 actual arguments
   print "Usage: $argv[0] param1 param2";
   die();
}
print "You entered $argv[1] and $argv[2].\n";

The first element of $argv (which starts counting from zero) will contain the name of the program being run, as called from the command line. So, if someone symlinks to your program and it is called that way, $argv[0] will contain the name of the symlink.

Finally, PHP can easily handle something like this:

$ codeprep | php > accounting.csv

...where the codeprep application is actually outputting php code. Naturally, PHP will read standard in like so:

$ ls -l | list_filter.php

The program list_filter.php would contain a loop like this:

while ($line = trim(fgets(STDIN))) {
   // Process input here
   print "$line\n";
}

Standard out is standard out: all echo and print statements are sent there automatically. But what if you want to 'do the right thing' and send error output via standard error? Easy: just use fwrite to direct output to that stream:

fwrite (STDERR, "Record number $rec_no is malformed\n");

With this in your code, you can still do this:

$ data_gen.php > datafile.csv
Record number 70 is malformed
Record number 103 is malformed

You still end up with a good data file, but also can be alerted to exceptions.

Conclusion

PHP is just one of the many nice ways to get into, or continue scripting under OS X. The brilliant thing is that OS X treats all scripting languages pretty equally. Additionally, if you're already familiar with PHP from web development, it makes a nice and easy transition into scripting for the system environment. PHP-based scripts can be used for anything that bash or perl scripts are: triggered automation from cron, GUI interaction and even our beloved login hooks.

Next month, we'll dip further into PHP, interaction with MySQL and other PHP-based script topics.

Media of the month: The Illustrated World's Religions: A Guide to Our Wisdom Traditions by Huston Smith. This one has been around for a bit, but its easy reading overviews and beautiful photography make this a good general read and nice reference guide. Once you see the different perspectives in this book, perhaps we end the emacs / vi wars!

Until next month, keep scripting.


Ed Marczak is the Executive Editor for MacTech Magazine, and has been lucky enough to have ridden the computing and technology wave from early on. From teletype computing to MVS to Netware to modern OS X, his interest was piqued. He has also been fortunate enough to come into contact with some of the best minds in the business. Ed spends his non-compute time with his wife and two daughters.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

BetterTouchTool 2.305 - Customize multi-...
BetterTouchTool adds many new, fully customizable gestures to the Magic Mouse, Multi-Touch MacBook trackpad, and Magic Trackpad. These gestures are customizable: Magic Mouse: Pinch in / out (zoom... Read more
calibre 3.8.0 - Complete e-book library...
Calibre is a complete e-book library manager. Organize your collection, convert your books to multiple formats, and sync with all of your devices. Let Calibre be your multi-tasking digital librarian... Read more
Carbon Copy Cloner 5.0.2 - Easy-to-use b...
Carbon Copy Cloner backups are better than ordinary backups. Suppose the unthinkable happens while you're under deadline to finish a project: your Mac is unresponsive and all you hear is an ominous,... Read more
Evernote 6.12.3 - Create searchable note...
Evernote allows you to easily capture information in any environment using whatever device or platform you find most convenient, and makes this information accessible and searchable at anytime, from... Read more
Default Folder X 5.1.6 - Enhances Open a...
Default Folder X attaches a toolbar to the right side of the Open and Save dialogs in any OS X-native application. The toolbar gives you fast access to various folders and commands. You just click on... Read more
Geekbench 4.1.2 - Measure processor and...
Geekbench provides a comprehensive set of benchmarks engineered to quickly and accurately measure processor and memory performance. Designed to make benchmarks easy to run and easy to understand,... Read more
GraphicConverter 10.5 - $39.95
GraphicConverter is an all-purpose image-editing program that can import 200 different graphic-based formats, edit the image, and export it to any of 80 available file formats. The high-end editing... Read more
Dropbox 35.4.20 - Cloud backup and synch...
Dropbox is an application that creates a special Finder folder that automatically syncs online and between your computers. It allows you to both backup files and keep them up-to-date between systems... Read more
XMind 8 Update 4 - Popular mind mapping...
XMind is the most popular mind mapping tool. Millions of people use XMind to clarify thinking, manage complex information, run brainstorming and get work organized. It couldn't be easier to get... Read more
Safari Technology Preview 11.1 - The new...
Safari Technology Preview contains the most recent additions and improvements to WebKit and the latest advances in Safari web technologies. And once installed, you will receive notifications of... Read more

The best new games we played this week -...
It's pretty much been one big release after another. We were privy to a bunch of surprises this week, with a lot of games we'd been waiting for quite some time dropping unexpectedly. We hope you're free this weekend, because there is a lot for... | Read more »
Stormbound: Kingdom Wars guide - how to...
Stormbound: Kingdom Wars is an excellent new RTS turned card battler out now on iOS and Android. Lovers of strategy will get a lot of enjoyment out of Stormbound's chess-like mechanics, and it's cardbased units are perfect for anyone who loves the... | Read more »
The best AR apps and games on iOS right...
iOS 11 has officially launched, and with it comes Apple's ARKit, a helpful framework that makes it easier than ever for developers to create mobile AR experiences. To celebrate the occassion, we're featuring some of the best AR apps and games on... | Read more »
Phoenix Wright: Ace Attorney - Spirit of...
Phoenix Wright: Ace Attorney - Spirit of Justice 1.00.00 Device: iOS Universal Category: Games Price: $.99, Version: 1.00.00 (iTunes) Description: ************************************************※IMPORTANT※・Please read the “When... | Read more »
Kpressor (Utilities)
Kpressor 1.0.0 Device: iOS Universal Category: Utilities Price: $4.99, Version: 1.0.0 (iTunes) Description: The ultimate ZIP compression application for iPhone and iPad. - Full integration of iOS 11 with support for multitasking.-... | Read more »
Find out how you can save £35 and win a...
Nothing raises excitement like a good competition, and we’re thrilled to announce our latest contest. We’ll be sending one lucky reader and a friend to the Summoners War World Arena Championship at Le Comedia in Paris on October 7th. It’s the... | Read more »
Another Lost Phone: Laura's Story...
Another Lost Phone: Laura's Story 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: Another Lost Phone is a game about exploring the social life of a young woman whose phone you have just... | Read more »
The Witness (Games)
The Witness 1.0 Device: iOS Universal Category: Games Price: $9.99, Version: 1.0 (iTunes) Description: You wake up, alone, on a strange island full of puzzles that will challenge and surprise you. You don't remember who you are, and... | Read more »
Egg, Inc. guide - how to build your gold...
Egg, Inc.'s been around for some time now, but don't you believe for one second that this quirky clicker game has gone out of style. The game keeps popping up on Reddit and other community forums thanks to the outlandish gameplay (plus, the... | Read more »
The best deals on the App Store this wee...
Good news, everyone! Your favorite day of the week has arrived at last -- it's discount roundup day! This fine Wednesday evening we're gathering up the hottest deals on the App Store. We've got action platformers, we've got puzzle games, we've got... | Read more »

Price Scanner via MacPrices.net

Apple Offering Up To $455 Credit Toward iPhon...
iPhone 8 and 8 Plus are now available at the Apple Store, and you can receive up to $375 credit toward a new iPhone purchase when you trade in your eligible smartphone. Photo Courtesy Apple Just... Read more
AnyTrans Offers iOS Users Three Ways For Movi...
iMobie Inc. today announceed AnyTrans v6.0.1, which now can help iOS users move all data to iPhone 8/8 Plus seamlessly. The software is available both on Mac and Windows and fully able to move all... Read more
Snag a 13-inch 2.3GHz MacBook Pro for $100 of...
B&H Photo has 2017 13″ 2.3GHz MacBook Pros in stock today and on sale for $100 off MSRP, each including free shipping plus NY & NJ sales tax only: – 13-inch 2.3GHz/128GB Space Gray MacBook... Read more
Verizon offers new iPhone 8 for $100-$300 off...
Verizon is offering the new iPhone 8 for up to $300 off MSRP with an eligible trade-in: • $300 off: iPhone 6S/6S Plus/7/7 Plus, Google Pixel XL, LG G6, Moto Z2 Force, Samsung Galaxy S7/S7 edge/S8/S8... Read more
Apple Refurbished 2017 13-inch MacBook Pros a...
Apple has Certified Refurbished 2017 13″ Touch Bar MacBook Pros in stock today and available for $200-$300 off MSRP. A standard Apple one-year warranty is included with each MacBook, and shipping is... Read more
OWC USB-C Travel Dock with 5 Ports Connectivi...
OWC have announced the new OWC USB-C Travel Dock, the latest addition to their line of connectivity solutions. The USB-C Travel Dock lets you connect its integrated USB-C cable to a Mac or PC laptop... Read more
Pelican Products, Inc. Unveils Cases For All...
Pelican Products, Inc. has announced the launch of its full line of cases including Voyager, Adventurer, Protector, Ambassador, Interceptor (for the Apple iPhone 8 and 8 Plus backwards compatible... Read more
$100 off new 2017 13-inch MacBook Airs
B&H Photo has 2017 13″ MacBook Airs on sale today for $100 off MSRP including free shipping. B&H charges NY & NJ sales tax only: – 13″ 1.8GHz/128GB MacBook Air (MQD32LL/A): $899, $100 off... Read more
Apple restocks Certified Refurbished 13-inch...
Apple has Certified Refurbished 2015 13″ MacBook Airs available starting at $719 and 2016 models available starting at $809. An Apple one-year warranty is included with each MacBook, and shipping is... Read more
Is iPhone X Really The Future Of The Smartpho...
Should iPhone X even be called a telephone? It does of course support telephony and texting, but its main feature set is oriented to other things. It is also debatable whether it makes any rational... Read more

Jobs Board

Specialist - Retail Customer Services and Sal...
The position listed below is not with Tennessee Interviews but with Apple , Inc. Tennessee Interviews is a private organization that works in collaboration with Read more
Specialist - Retail Customer Services and Sal...
The position listed below is not with South Carolina Interviews but with Apple , Inc. South Carolina Interviews is a private organization that works in collaboration Read more
Behavior Technician with *Apple* Consulting...
The position listed below is not with Washington Interviews but with APPLE CONSULTING Washington Interviews is a private organization that works in collaboration Read more
Infection Control RN with *Apple* Rehab - A...
The position listed below is not with Georgia Interviews but with Apple Rehab Georgia Interviews is a private organization that works in collaboration with Read more
Specialist - Retail Customer Services and Sal...
The position listed below is not with South Carolina Interviews but with Apple , Inc. South Carolina Interviews is a private organization that works in collaboration Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.