ECA 236

1. ECA 236 Open Source Server Side Scripting Files & Directories Open Source Server Side Scripting

2. flat files • 2 ways of storing information • flat files • databases • advantages of flat files • no specific knowledge of databases required • no extra charge Open Source Server Side Scripting

3. flat files cont … • disadvantages of flat files • slow when working with large files • searching is difficult and slow • problems allowing more than one user simultaneous access • files are processed sequentially • difficult to allow different levels of access Open Source Server Side Scripting

4. permissions • directory access ( permissions ) may be granted to: • owner: generally has permission to read and write • groups: users can be organized into groups • world: everyone else • types of file permissions • r readable • w writeable • x executable Open Source Server Side Scripting

5. file processing • to write to a file • open the file – create it if it does not already exist • write data to the file • close the file • to read from a file • open the file – if it cannot be opened, exit gracefully • read data from the file • close the file Open Source Server Side Scripting

6. opening a file • fopen( ) takes two parameters • the file to be opened • the mode in which to open it • path to file name • create a variable to hold the path to the file • $_SERVER[ 'DOCUMENT_ROOT‘ ] contains the document root directory • $dir_name = dirname($_SERVER["PHP_SELF"]); Open Source Server Side Scripting

7. opening a file • path to file name • create a variable to hold the path to the file • $_SERVER[ 'DOCUMENT_ROOT‘ ] contains the document root directory • $dir_name = dirname($_SERVER["PHP_SELF"]); $doc_root = $_SERVER["DOCUMENT_ROOT"]; $dir_name = dirname($_SERVER["PHP_SELF"]); $fp = fopen( $doc_root . $dir_name . "/dogs_1.txt", 'w' ) or die ( “Cannot open the file” ); Open Source Server Side Scripting

8. opening a file cont … • fopen( ) takes 4 parameters the 3rd and 4th are optional • the file to be opened • the mode in which to open it • search option • option to open file in remote location • mode • indicates the purpose for opening the file • read • write • overwrite • append • both Open Source Server Side Scripting

9. opening a file cont … Open Source Server Side Scripting

10. opening a file cont … Open Source Server Side Scripting

11. opening a file cont … • assign the fopen( ) call to a file pointer • use the file pointer to refer to the open file • if the file cannot be opened • the @ operator suppresses the notice • die( ) is called to generate error message and stop execution of script, thus exiting gracefully @ $fp = fopen( $file_name, "w" ) or die ( “Cannot open the file” ); Open Source Server Side Scripting

12. writing to a file • fwrite( ) takes three parameters, the third is optional • file pointer • string which will be written to the file • maximum number of bytes • if exceeded, PHP truncates the output string fwrite( $fp, $string_output, 1000 ); Open Source Server Side Scripting

13. writing to a file cont … • separate the sections of data with a delimiter • pipe, comma, tab, etc • if the data will be used in another application, follow the rules of the other application • the delimiter should not be one which may be used in the user’s input • end the string with a record separator (newline ) $string_output = “$name|$gender|$height|$weight|$age\n”; Open Source Server Side Scripting

14. closing the file • use the fclose( ) function to close the file • fclose( ) takes one parameter, the file pointer fclose( $fp ); Open Source Server Side Scripting

15. reading from a file • open the file with the fopen( ) function • use the correct mode to write to the file @ $fp = fopen( $file_name, “r" ) or die ( “Cannot open the file” ); if ( filesize( "$doc_root/files/file_name.txt“ ) != 0 ){ while( !feof( $fp ) ) { $line = fgets( $fp, 1000 ); echo $line . “<br />”; } //end while } // end if fclose( $fp ); Open Source Server Side Scripting

16. reading from a file cont … • if the file opens correctly, read from the file until the end of the file is reached • feof( ) returns TRUE when the end of the file is reached • feof( ) takes one parameter, the file pointer while( !feof( $fp ) ) { Open Source Server Side Scripting

17. reading from a file cont … • when using feof( )check to see if the filesize is 0 • if the filesize is zero an infinite loop is generated • if there is a problem opening the file an infinite loop is generated • filesize( ) returns the size of the file in bytes • filesize( ) takes one parameter, the path to the file if ( filesize("$doc_root/files/file_name.txt" != 0 ){ Open Source Server Side Scripting

18. reading from a file cont … • fgets( ) reads from the file one line at a time • fgets( ) takes two parameters, the second is optional • the file pointer • maximum number of bytes to be returned • fgets( ) returns each line as a string $line = fgets( $fp, 1000 ); Open Source Server Side Scripting

19. reading from a file cont … • fgetss( ) reads from the file one line at a time • fgetss( ) takes three parameters, the third is optional • the file pointer • maximum number of bytes to be returned • allowable tags • fgetss( ) returns each line as a string, with HTML and PHP removed $line = fgetss( $fp, 1000 ); Open Source Server Side Scripting

20. reading from a file cont … • fgetcsv( ) reads from the file one line at a time • fgetcsv( ) takes four parameters, the third and fourth are optional • the file pointer • maximum number of bytes to be returned • delimiter ( defaults to comma ) • enclosure ( defaults to double quotation marks ) • fgetcsv( ) returns each line as an array, separated on the delimiter $line_array = fgetcsv( $fp, 1000, “|” ); Open Source Server Side Scripting

21. reading from a file cont … • readfile( ) • opens the file • echoes entire file to browser • closes file • no need to manually open and close file • readfile( ) takes the path to the file as an argument readfile( "$doc_root/files/file_name.txt" ); Open Source Server Side Scripting

22. reading from a file cont … • file( ) • opens the file • file is returned as an array, each line as an array element ( newline is still attached ) • closes file • no need to manually open and close file • file( ) takes the path to the file as an argument $file_array = file( "$doc_root/files/file_name.txt" ); Open Source Server Side Scripting

23. reading from a file cont … • file_get_contents( ) • opens the file • file is returned as a string • closes file • no need to manually open and close file • file_get_contents( ) takes the path to the file as an argument $file_string = file_get_contents( "$doc_root/files/file_name.txt" ); Open Source Server Side Scripting

24. reading from a file cont … • fgetc( ) takes one parameter • file pointer • fgetc( ) returns one character at a time • in addition to string characters, fgetc( ) reads newline and eof characters $char = fgetc( $fp ); Open Source Server Side Scripting

25. reading from a file cont … • file_exists( ) • checks whether a file or directory exists • returns Boolean TRUE if it exists • FALSE if it does not • file_exists( ) takes the path to the file as an argument file_exists( "$doc_root/files/file_name.txt" ); Open Source Server Side Scripting

26. reading from a file cont … • unlink( ) • deletes a file • unlink( ) takes the path to the file as an argument unlink( "$doc_root/files/file_name.txt" ); Open Source Server Side Scripting

27. file locking • flock( ) takes two parameters • file pointer • a constant indicating the kind of lock to acquire Open Source Server Side Scripting

28. security • to create a file in a directory above the document root • make sure directory exists before writing to it • test it carefully on your server $doc_root = $_SERVER[ 'DOCUMENT_ROOT' ];$file_name ="$doc_root/../files/file_name.txt";$fp = fopen( $file_name, "w+" ); Open Source Server Side Scripting

29. security cont … • crypt( ) function • one-way algorithm to encrypt a string value • no function to decrypt the string • crypt( ) takes two arguments • string to be encrypted • salt string • salt does not work the same on different systems Open Source Server Side Scripting

30. security cont … • crypt( ) function • given the same string and the same salt, the same encrypted result is returned each time • we do not need to know the original value of the encrypted string • compare encrypted result to password entered by user after running through the crypt( ) function, with the stored, encrypted password as the salt if( crypt( $user_entered_pw, $enc_pw_stored ) == $enc_pw_stored ) { // code if passwords match} Open Source Server Side Scripting