Updated exit codes as constant values

Re-allocated exit status codes according to three references, which follow:

BSD sysexits.h:http://www.gsp.com/cgi-bin/man.cgi?section=3&topic=sysexits
GNU recomendations:http://www.gnu.org/software/libc/manual/html_node/Exit-Status.html
Bash scripting:http://tldp.org/LDP/abs/html/exitcodes.html

The GNU recommendations stem from and expand upon the standard C/C++ library (stdlibc)
definitions, while also suggesting some best-practice conventions which happen to prevent
exit status code collisions with bash, and probably other shells.

The re-allocated codes are now mapped to constant values, set in *application/config/constants.php*,
and used throughout the CodeIgniter core.  They would additionally be used in *index.php*,
but the constants file hasn't been loaded at that point, so the integer values are used
instead, and a comment follows each such use with amplifying information on why that
particular value was selected.

Finally, the errors documentation has been updated accordingly.

Signed-off-by: Daniel Hunsaker <danhunsaker@gmail.com>

1 files changed, 8 insertions, 4 deletions

diff --git a/index.php b/index.php
index be0945740..a52a021ec 100755
--- a/index.php
+++ b/index.php
@@ -67,7 +67,8 @@ switch (ENVIRONMENT)
 
 	default:
 		header('HTTP/1.1 503 Service Unavailable.', TRUE, 503);
-		exit('The application environment is not set correctly.');
+		echo 'The application environment is not set correctly.';
+		exit(1); // EXIT_* constants not yet defined; 1 is EXIT_FAILURE, a generic error.
 }
 
 /*
@@ -190,7 +191,8 @@ switch (ENVIRONMENT)
 	if ( ! is_dir($system_path))
 	{
 		header('HTTP/1.1 503 Service Unavailable.', TRUE, 503);
-		exit('Your system folder path does not appear to be set correctly. Please open the following file and correct this: '.pathinfo(__FILE__, PATHINFO_BASENAME));
+		echo 'Your system folder path does not appear to be set correctly. Please open the following file and correct this: '.pathinfo(__FILE__, PATHINFO_BASENAME);
+		exit(3); // EXIT_* constants not yet defined; 3 is EXIT_CONFIG.
 	}
 
 /*
@@ -225,7 +227,8 @@ switch (ENVIRONMENT)
 		if ( ! is_dir(BASEPATH.$application_folder.'/'))
 		{
 			header('HTTP/1.1 503 Service Unavailable.', TRUE, 503);
-			exit('Your application folder path does not appear to be set correctly. Please open the following file and correct this: '.SELF);
+			echo 'Your application folder path does not appear to be set correctly. Please open the following file and correct this: '.SELF;
+			exit(3); // EXIT_* constants not yet defined; 3 is EXIT_CONFIG.
 		}
 
 		define('APPPATH', BASEPATH.$application_folder.'/');
@@ -241,7 +244,8 @@ switch (ENVIRONMENT)
 		elseif ( ! is_dir(APPPATH.'views/'))
 		{
 			header('HTTP/1.1 503 Service Unavailable.', TRUE, 503);
-			exit('Your view folder path does not appear to be set correctly. Please open the following file and correct this: '.SELF);
+			echo 'Your view folder path does not appear to be set correctly. Please open the following file and correct this: '.SELF;
+			exit(3); // EXIT_* constants not yet defined; 3 is EXIT_CONFIG.
 		}
 		else
 		{