FINDSTR: Line is too long

Solution 1:

SS64's FINDSTR - Escapes and Length limits says:

Line Length limits

Files specified as a command line argument or via the /F:FILE option have no known line length limit. Searches were successfully run against a 128MB file that did not contain a single <LF>.

Piped data and Redirected input is limited to 8191 bytes per line. This limit is a "feature" of FINDSTR. It is not inherent to pipes or redirection. FINDSTR using redirected stdin or piped input will never match any line that is >=8k bytes. Lines >= 8k generate an error message to stderr, but ERRORLEVEL is still 0 if the search string is found in at least one line of at least one file.

Credits:
Dave Benham - List of undocumented features and limitations of FINDSTR from StackOverflow

Solution 2:

The better built-in alternative would be PowerShell's Select-String (or its alias sls)

The Select-String cmdlet searches for text and text patterns in input strings and files. You can use Select-String similar to grep in UNIX or findstr.exe in Windows.

Select-String

Just be aware that Select-String does a case-insensitive search by default, unlike most alternatives