How can I list only files that begin with "/LOG?"

Question

Trying to list root directory of LittleFS; but only files beginging with "/LOG."

String str;
 if (!LittleFS.begin())
 {
 Serial.println("LittleFS failed to mount !");
 }
 Dir dir = LittleFS.openDir("/");
 while (dir.next())
 {
 if(strncmp(dir.fileName().c_str(), "/LOG", 4) == 0)
 {
 str += "<a href=\"";
 str += dir.fileName();
 str += "\">";
 str += dir.fileName();
 str += "</a>";
 str += " ";
 str += dir.fileSize();
 str += "<br>\r\n";
 }
 }
 client.print(str);

If I comment out "if(strncmp(dir.fileName().c_str(), "/LOG", 4) == 0)" and associated braces; all files list. Code with "if(strncmp(dir.fileName().c_str(), "/LOG", 4) == 0)" no files are listed.

How can I list only files that begin with "/LOG?"

William

• Majenko: And you're sure that the filenames do begin with precisely the characters /LOG ?
• Kwasmich: Just a sanity check here. But isn't / used as path separator? In my world / is an invalid character for file or directory names. Listed file names in directory / should not contain / then.
• Majenko: @Kwasmich Unless the result of dir.fileName() is the fully qualified absolute path of the file. Which is why I was asking if the filenames really do start /LOG
• Kwasmich: @Majenko true. Just to make sure nothing gets overlooked. strncmp is case-sensitive!
• Majenko: @Kwasmich Indeed. Not a problem if it's using 8.3 filenames, but could be a problem if the FS uses LFN.

Answer 1

Give a filename String to text...

String text = "/LOGsdfsdf";
if(text.startsWith("/LOG")){
//wee file begins with /LOG
}else{
// wops wrong file.
}

Look in here

https://www.arduino.cc/reference/en/language/variables/data-types/stringobject/

Method url startsWith("");

https://www.arduino.cc/reference/en/language/variables/data-types/string/functions/startswith

• William: FileZilla shows filename as "LOG0608.TXT." Naming convention is "LOG + Month + Date + '.TXT'." I could have carried the "/" over from the web server.
• William: Need "dir.fileName()" to compare acutal filename to LOG0608.TXT. I only want files starting with "LOG" to be displayed.
• Avon97: Dose dir.fileName() gives a string as "LOGXXXX.TXT" or "/LOGXXXX.TXT"
• William: Used: String file_name = dir.fileName(); if(file_name.startsWith("LOG")) { Thanks!
• Avon97: gr8 glad I can help you