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Lecture 11 Log into Linux, also log into csserver Reminder: Project 3 due next Tuesday Questions? Thursday, September 30 CS 375 UNIX System Programming - Lecture 11 1 Outline More PHP Remote files Directory operations

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Thursday, September 30 CS 375 UNIX System Programming - Lecture 11 1

Lecture 11

 Log into Linux, also log into csserver  Reminder: Project 3 due next Tuesday  Questions?

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Thursday, September 30 CS 375 UNIX System Programming - Lecture 11 2

Outline

 More PHP  Remote files  Directory operations  Functions  Variable scope  Interacting with the OS  Regular expression matching and

substitution

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Thursday, September 30 CS 375 UNIX System Programming - Lecture 11 3

Remote Files

 Since PHP was designed for use with web

servers, the fopen( ) command can be used to access remote files by giving a URL instead of a local file name.

$slash = fopen("http://www.slashdot.org", "rt"); $site = fread($slash, 200000); // 1st 200K bytes fclose($slash); print $site;

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Thursday, September 30 CS 375 UNIX System Programming - Lecture 11 4

Directory Operations

 PHP directory operations are similar to C:

pendir( ), readdir( ), and closedir( ).

$handle = opendir ("."); // current dir if ($handle) { // check that open succeeded while (false !== ($filename = readdir($handle))){ if ($filename != "." && $filename != "..") print "$file\n"; } closedir ($handle); }

 The use of !== (not identical to) is to handle the

possibility that a directory entry name evaluates to false.

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Thursday, September 30 CS 375 UNIX System Programming - Lecture 11 5

Directory Operations

 Other directory operations include:

 mkdir ( ) - create a directory  rmdir ( ) - remove an empty directory  get_cwd ( ) - get the current working directory  chdir ( ) - change directories

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Thursday, September 30 CS 375 UNIX System Programming - Lecture 11 6

Functions

 PHP functions are defined as in C++ without

the types using the function keyword. Has both value and reference parameters.

function foo ($arg1, &$arg2) { $result = ...; // local variable ... return $result; }

 Function definitions can appear anywhere in

the script.

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Thursday, September 30 CS 375 UNIX System Programming - Lecture 11 7

Default Parameters

 PHP has default parameters

function doHello ($name = "Mary") { return "Hello $name!"; } doHello(); // "Hello Mary!" doHello("John"); // "Hello John!"

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Thursday, September 30 CS 375 UNIX System Programming - Lecture 11 8

Variable Arguments

 A PHP function may be called with more arguments

than listed in its header. The extra arguments can be accessed using functions func_num_args( ), func_get_arg( ), and func_get_args( ).

function someFunc ($a) { for ($i = 0; $i < func_num_args(); ++$i) { $param = func_get_arg($i); print "Received parameter $i: $param\n"; } $params = func_get_args(); $paramlist = implode(",", $params); print "Received parameters: $paramlist\n"; } someFunc (5,4,3,2,1);

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Thursday, September 30 CS 375 UNIX System Programming - Lecture 11 9

Variable Scope

 In PHP, any variable not set inside a function is

considered global. That is, they are accessible from anywhere else in the script, except inside a function.

 In particular, this means that variables span any

code islands in the script

 Variables set inside functions are local to that

function.

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Thursday, September 30 CS 375 UNIX System Programming - Lecture 11 10

Superglobal Variables

 Special variables like $_SERVER are called

superglobals, since they are accessible anywhere, including inside functions.

 $GLOBALS is a superglobal associative array

that gives access to any global variable. The name of the variable is the index.

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Thursday, September 30 CS 375 UNIX System Programming - Lecture 11 11

Scope Examples

$bar = "baz"; print "global \$bar is: $bar\n"; // baz foo1(); print "global \$bar is: $bar\n"; // baz print "global \$foo is: $foo\n"; // null foo2(); print "global \$bar is: $bar\n"; // wombat function foo1 () { print "local \$bar is: $bar\n"; // null $foo = "foo"; print "local \$foo is: $foo\n"; // foo } function foo2 () { $GLOBALS['bar'] = "wombat"; }

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Thursday, September 30 CS 375 UNIX System Programming - Lecture 11 12

Interacting with the OS

 Backticks (`) can be used to run external

commands, including using redirection or pipes .

$cwd = `pwd`; print "Current directory is $cwd\n"; print "The files in the directory:\n"; print `ls`;

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Thursday, September 30 CS 375 UNIX System Programming - Lecture 11 13

Regular Expression Matching

 When the basic string operations are not

enough, PHP provides regular expression (regexp) matching. The basic regexp function is preg_match( ) that has two parameters, the pattern to match and the string to match it

against. It returns true after the first match;

false if there is no match.

 Regexps are formed by starting and ending

with a (forward) slash. E.g., "/php/"

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Thursday, September 30 CS 375 UNIX System Programming - Lecture 11 14

Regexp Special Characters

 The special characters used to form regexps

are similar to those used in shell globbing or grep.

\ De-special the next character | Alternation (or) () Group [] A character class ^ Match at beginning of string $ Match at end of string . Match any one character, except \n

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Thursday, September 30 CS 375 UNIX System Programming - Lecture 11 15

Regexp Quantifiers

 Quantifiers indicate how many times the

preceding item should match.

* Match 0 or more times + Match 1 or more times ? Match 0 or 1 times {COUNT} Match exactly COUNT times {MIN,} Match at least MIN times {MIN,MAX} Match between MIN and MAX times

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Thursday, September 30 CS 375 UNIX System Programming - Lecture 11 16

Regexp Examples

 Here are some regexp examples:

"/Gandalf|Saruman/" # Match either "/pro(b|r)ate/" # probate or prorate "/\..$/" # file.a, xxx.b, etc at end "/could(n't)?/" # Match could or couldn't "/^ba(na)*/" # At start: ba,bana,... "/ba(na){2}/" # banana

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Thursday, September 30 CS 375 UNIX System Programming - Lecture 11 17

Regexp Modifiers

 A regular expression can be followed by

modifiers that affect the way matches are computed.

 Common modifiers include

i Case insensitive m Let ^ and $ match next to embedded \n

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Thursday, September 30 CS 375 UNIX System Programming - Lecture 11 18

Modifier Examples

preg_match("/php/", "php"); // true preg_match("/php/", "PHP"); // false preg_match("/php/i", "PHP"); // true preg_match("/Php/i", "PHP"); // true $multiline = "This is\na long test\nto see whether\nthe dollar\nSymbol\nand the\ncaret\nwork as planned"; preg_match("/is$/", $multiline); // false preg_match("/is$/m", $multiline); // true

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Thursday, September 30 CS 375 UNIX System Programming - Lecture 11 19

Regexp Symbols

 There are special symbols that can be used

inside regular expressions. Most common ones:

\b Match word boundary \B Match non-word boundary \s Match any whitespace \S Match any non-whitespace \A Match string beginning (^) \Z Match string end ($)

 The last two are used with multi-line strings ('m'

modifier) where ^ and $ will match each line rather than the whole string.

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Thursday, September 30 CS 375 UNIX System Programming - Lecture 11 20

Regular Expression Substitution

 The function to use regexps to identify text to

be replaced is preg_replace( ), which takes 3 arguments, the regexp, the replacement string, and the string to work with. It returns a string with the matches replaced.

 The replacement string can contain $n to refer

to the match of subpattern n of the regexp rule. $0 refers to the entire matched text.

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Thursday, September 30 CS 375 UNIX System Programming - Lecture 11 21

Substitution Examples

$a = "Foo moo boo tool foo"; $b = preg_replace("/[A-Za-z]oo\b/", "Got word: $0\n", $a); print $b; // Output: // Got word: Foo // Got word: moo // Got word: boo // tool Got word: foo $match = "/the (car|cat) sat on the (drive|mat)/"; $input = "the cat sat on the mat"; print preg_replace($match, "Matched $0, $1, and $2\n", $input); // Output: Matched the cat sat on the mat, cat, and mat

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Thursday, September 30 CS 375 UNIX System Programming - Lecture 11 22

In-class Exercise

 Write a PHP program that tests whether or not

an argument is a valid phone number (based

n its format) and print an appropriate

message.

 The following should be considered valid phone

Lecture 11

Outline

substitution

Remote Files

servers, the fopen( ) command can be used to access remote files by giving a URL instead of a local file name.

Directory Operations

possibility that a directory entry name evaluates to false.

Directory Operations

Functions

the types using the function keyword. Has both value and reference parameters.

function foo ($arg1, &$arg2) { $result = ...; // local variable ... return $result; }

the script.

Default Parameters

function doHello ($name = "Mary") { return "Hello $name!"; } doHello(); // "Hello Mary!" doHello("John"); // "Hello John!"

Variable Arguments

than listed in its header. The extra arguments can be accessed using functions func_num_args( ), func_get_arg( ), and func_get_args( ).

Variable Scope

considered global. That is, they are accessible from anywhere else in the script, except inside a function.

code islands in the script

function.

Superglobal Variables

superglobals, since they are accessible anywhere, including inside functions.

that gives access to any global variable. The name of the variable is the index.

Scope Examples

Interacting with the OS

commands, including using redirection or pipes .

$cwd = `pwd`; print "Current directory is $cwd\n"; print "The files in the directory:\n"; print `ls`;

Regular Expression Matching

enough, PHP provides regular expression (regexp) matching. The basic regexp function is preg_match( ) that has two parameters, the pattern to match and the string to match it

false if there is no match.

with a (forward) slash. E.g., "/php/"

Regexp Special Characters

are similar to those used in shell globbing or grep.

\ De-special the next character | Alternation (or) () Group [] A character class ^ Match at beginning of string $ Match at end of string . Match any one character, except \n

Regexp Quantifiers

preceding item should match.

* Match 0 or more times + Match 1 or more times ? Match 0 or 1 times {COUNT} Match exactly COUNT times {MIN,} Match at least MIN times {MIN,MAX} Match between MIN and MAX times

Regexp Examples

"/Gandalf|Saruman/" # Match either "/pro(b|r)ate/" # probate or prorate "/\..$/" # file.a, xxx.b, etc at end "/could(n't)?/" # Match could or couldn't "/^ba(na)*/" # At start: ba,bana,... "/ba(na){2}/" # banana

Regexp Modifiers

modifiers that affect the way matches are computed.

i Case insensitive m Let ^ and $ match next to embedded \n

Modifier Examples

Regexp Symbols

inside regular expressions. Most common ones:

\b Match word boundary \B Match non-word boundary \s Match any whitespace \S Match any non-whitespace \A Match string beginning (^) \Z Match string end ($)

modifier) where ^ and $ will match each line rather than the whole string.

Regular Expression Substitution

be replaced is preg_replace( ), which takes 3 arguments, the regexp, the replacement string, and the string to work with. It returns a string with the matches replaced.

to the match of subpattern n of the regexp rule. $0 refers to the entire matched text.

Substitution Examples

In-class Exercise

an argument is a valid phone number (based

message.

numbers: (123)456-7890, 123-456-7890, (123)4567890, 123 456 7890, 123.456.7890, 1234567890, etc.