Function diffSystemLogContents

Computes the difference between two system log contents by returning only the new lines added after the last known line from the old content.

Returns

A string containing only the new lines from newContent that come after the reference line from oldContent. If the reference line is not found, returns the entire newContent.

Example

const oldLog = 'line1\nline2\nline3';
const newLog = 'line1\nline2\nline3\nline4\nline5';
const diff = diffSystemLogContents(oldLog, newLog);
console.log(diff); // → 'line4\nline5'

Remarks

• Useful for incremental log processing where only newly appended lines need to be handled.
• Handles negative indexing for selecting the reference line from the end of oldContent.