Temporary Log Files

When new software is written and installed, logging its variable values as they are used can help find bugs, should they occur, or if someone attempts to use the software in ways it was not meant to operate. The log file then contains a record of software activity.

This is most applicable to software that you write. Other people's software might also be updated to log certain activity when the person doing the updating is sufficiently skilled and understands how the software works.

This is how I do it for software I write.

Near the top of the script are these 2 lines:

$DebugFile = false;
$DebugFile = __DIR__ . '/' . time() . '_SoftwareName.txt';

The first of the above two lines gives $DebugFile the value false. The second of the two lines gives $DebugFile the value of a file name for the log file.

The reason I do it this way is to make it easy to turn logging off and on.

Generally, I will have logging lines throughout the software. Without the ability to easily turn logging off and on at one point in the script, I would need to locate every individual logging line and then disable or enable it.

To turn logging off, place a # character in front of the second line. To turn logging back on, remove the # character.

Now you are ready to insert the lines that will cause entries in the log file.

Here is a template:

if($DebugFile) { file_put_contents($DebugFile,__LINE__.":\n".INFORMATION."\n\n",FILE_APPEND); }

To use the above template, replace INFORMATION with whatever should be logged. Insert the updated line into the software at the point where logging should occur.

The first logging line I generally log is a date/timestamp. For that INFORMATION is replaced with the date('r') command.

if($DebugFile) { file_put_contents($DebugFile,__LINE__.":\n".date('r')."\n\n",FILE_APPEND); }

To log the value of a scalar variable, replace INFORMATION with the variable name. To publish the value of a variable $MyName, for example, the logging line would be.

if($DebugFile) { file_put_contents($DebugFile,__LINE__.":\n".$MyName."\n\n",FILE_APPEND); }

Place the logging line where $MyName is available and at the point where you want to know its value.

To log the value of an array variable, replace INFORMATION with the print_r() function for the array. To publish the value of array $Months, for example, use print_r($Months). Example:

if($DebugFile) { file_put_contents($DebugFile,__LINE__.":\n".print_r($Months)."\n\n",FILE_APPEND); }

The print_r() function prints each value of the array into the log file.

Place your modified log lines into your software wherever you need or want to know the values of variables. They can be invaluable when chasing down an anomaly.

(This content first appeared in Possibilities newsletter.)

Will Bontrager