Reading text file and appending to start

Question

var file = File(myFilePath);file.open("a", "TEXT");//alert("file opened! it is: 
" + file);while (!file.eof){ // Loop doesn't trigger here    var line = file.readln();    alert("line is:
" + line);}file.close();myFilePath is a string containing a file path to a text file on my disk.Two questions here:1) Why doesn't the while loop trigger? Is the position eof by default when opening up a file for append? ("a")2) How do I open up a file for append-to-start ("a+")The case is this:I have an already existing file with some object properties. I want to open up said file and add additional properties to the top/start of it.

JJMack · Accepted Answer

Does this script alert help?What new eyes can do but mine are 75 years old with new lens though new is good.

Anonymous · Answer

1) Why doesn't the while loop trigger? Is the position eof by default when opening up a file for append? ("a")
2) How do I open up a file for append-to-start ("a+")

1) From https://www.adobe.com/content/dam/Adobe/en/devnet/scripting/pdfs/javascript_tools_guide.pdf :

fileObj.open (mode[,type][,creator])

mode: A string indicating the read/write mode. One of:

- r: (read) Opens for reading. If the file does not exist or cannot be found, the call fails.

- w: (write) Opens a file for writing. If the file exists, its contents are destroyed. If the file does not exist, creates a new, empty file.

- e: (edit) Opens an existing file for reading and writing.

- a: (append) Opens the file in Append mode, and moves the current position to the end of the file.

2) Use the edit mode instead: "e"

var file = File (myFilePath);
if (file.open ("e"))
{
    var position = file.tell ();
    var contents = file.read ();
    file.seek (position);
    file.writeln ("Inserted Text");
    file.write (contents);
    file.close ();
}

Please note that right after opening the file in edit mode, the current position is not necessarily 0, since the text may be preceded by an invisible BOM (Byte-Order-Mark). In the case of UTF-8 encoding, for instance, 3 extra bytes (0xEF, 0xBB, 0xBF) may need to be skipped.

HTH,

--Mikaeru

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