Analyzing a Streamed Log by Splitting Based on Indexes

I am facing an issue with log files that are saved as raw text without any control over how they were written. These log files store data in a streaming manner, making it challenging to parse the content where each line begins with an index.

Upon examining the log files and expected output provided below, I noticed that they always start with a 13-digit index (possibly padded), which I assumed as the starting point for each line. My approach involved splitting the content using this index to process the initial lines. However, while implementing this solution in a loop, I realized that my usage of split was incorrect as it only identifies line endings rather than beginnings.

Despite this setback, I am looking for an easy fix to refine my current approach and achieve the desired outcome. Any suggestions or guidance on enhancing this partial solution would be greatly appreciated.

var reader = new FileReader();
var output = [];

reader.readAsText(f, "UTF-8");

            // if file read successful then text string stored in the result property of FileReader()
            reader.onload = function(evt){
                var fileContents = evt.target.result;
                var index = fileContents.slice(0,13);
                var lines = fileContents.split(index);

                // Continue splitting until we fail (nothing split = 1)
                //while(lines.length > 1){
                    for(var i = 0; i < lines.length; i++){
                        output.push(index + ' ' + lines[i] + '<br>')
                    }

                    // go to next lines
                    index++;
                    lines = fileContents.split(index);
                //}

                document.getElementById('content').innerHTML = '<ul>' + output.join('') + '</ul>';
            }

Content of the provided log file:

1564001512016 INFO: LOG MANAGER jdshfkjaafhdskfdsajfdsadsfj 1564001512016 INFO: some test stuff 1564001512016 INFO: kjhdshfakhfdskjdshkjfdsh 1564001517 INFO: hjkdsahfjkfhdskjfdsahkfdskjfdsakjfds 1564001517 INFO: hdskjahfjfdshdfsahfdsajfdsa

Current Output:


1564001512016 INFO: LOG MANAGER jdshfkjaafhdskfdsajfdsadsfj
1564001516 INFO: some test stuff 
1564001516 INFO: kjhdshfakhfdskjdshkjfdsh 1564001517 INFO: hjkdsahfjkfhdskjfdsahkfdskjfdsakjfds 1564001517 INFO: hdskjahfjfdshdfsahfdsajfdsa

Desired Output:

1564001512016 INFO: LOG MANAGER jdshfkjaafhdskfdsajfdsadsfj 
1564001516 INFO: some test stuff
1564001516 INFO: kjhdshfakhfdskjdshkjfdsh 
1564001517 INFO: hjkdsahfjkfhdskjfdsahkfdskjfdsakjfds 
1564001517 INFO: hdskjahfjfdshdfsahfdsajfdsa

Update: Addressing the provided answer, I tailored the code snippet below accordingly. Notable modifications include reintroducing the 'INFO' string removed by split and assigning the value of 'i' to a variable 'x' to prevent incrementation at every iteration:

                var fileContents = evt.target.result;
                var regex = /(\d{13}) INFO:/
                var lines = fileContents.split(regex);

                // Starting from 1 as split consistently returns empty at index 0
                for(var i = 1; i < lines.length; i+=2){
                    var x = i;
                    var index = lines[x]
                    var context = lines[x+1]
                    // \xa0 = space
                    output.push('<li>' + index + "\xa0INFO:\xa0\xa0" + context + '</li>')
                }
                document.getElementById('content').innerHTML = output.join('') + '</br>';

Final Output:

1564001512016 INFO:  LOG MANAGER jdshfkjaafhdskfdsajfdsadsfj
1564001516 INFO:  some test stuff
1564001516 INFO:  kjhdshfakhfdskjdshkjfdsh 
1564001517 INFO:  hjkdsahfjkfhdskjfdsahkfdskjfdsakjfds 
1564001517 INFO:  hdskjahfjfdshdfsahfdsajfdsa

Answer №1

Due to the constantly changing index and absence of line endings in the log message, it is challenging to accurately parse this file. However, one approach is to utilize regular expressions:

var pattern = /(\d{13}) INFO:/
var segments = fileContents.split(pattern);

for(var j = 1; j < segments.length; j+=2){
    var codeIndex = segments[j];
    var textLine = segments[j+1];
    // ...
}

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