In what situation should I use ASCII to transfer a

Question

I understand the difference between ASCII mode vs binary when it comes to FTP, but what I don't understand is why there is even a need for ASCII mode at all? Is this just a legacy thing that used to save time by eliminating the most significant bit, therefore causing the overall speed of the transfer to increase by 1/8th? Or is there some hidden use for it that I don't know about?

I've encountered many problems because I would forget to switch the mode to bin when transferring text between different OS's. I don't understand why "bin" isn't just the default for everything, especially with today's much faster internet speeds.

Knowwutimean, Vern?

Answer 1

ASCII mode exists so you can get the right answer when you upload a text file to a remote system without having to know what the line termination or character set conventions are for that system. It was more important when transferring text files was more often done via FTP than, say, email.

To address your practical problem: check the documentation for both your FTP client and server(s) to see if there's a way to set ASCII mode by default. Often this is as simple as some kind of "profile" that sends some FTP commands every time you connect.

To address your philosophical problem: FTP is a 40 year old protocol that has its fair share of historical baggage. One day you'll be very glad that some protocol you depend on was standardized long ago and you can still access some old data.

Answer 2

Here's a practical example of a problem that comes from using a binary FTP connection. In php there are two types of comments:

// a single line comment like this
/* a block comment like this */

The block comment has a start and an end. But the single line comment just ends at the end of the line.

If you upload a php file with single line comments using a binary connection, the php will stop running as soon as it hits the single line comment. It doesn't recognise the end of the line as the end of the comment, so it effectively comments out the rest of your php script.

If however you use FTP in ASCII mode, it will correctly read the end of the line and will run your php code as expected.

Answer 3

One scenario of practical use of ASCII mode is to upload PHP or Perl or similar scripts from Windows development machine to Unix server. Use of Binary mode would require separate conversion of line ending sequences, while with ASCII mode conversion is performed "automatically".

Update: there's one more scenario that we have come across - when transferring data to/from mainframes that use EBCDIC encoding, ASCII mode tells the server to perform conversion between encodings.

Answer 4

I, for one, vote to eliminate ascii mode from ftp servers. Any EOL translation can be done by applications consuming the files, and many apps today understand both EOL types anyway. At a minimum, I'd like to see servers switch to using binary by default, and only use ascii if requested.