Internet Support

Epsilon for Windows or Unix has several commands and facilities that make it easy for you to edit files on other computers using the Internet.

The find-file and dired commands, as well as a few others, understand Internet URLs. If you provide the URL ftp://user@example.com/myfile.c to a file-reading command like find-file, Epsilon will engage in an FTP interaction to download the file and display it in a buffer. All of the Internet activity happens in the background, so you don't have to wait for the file to download before continuing with your work. In fact, the file appears in the buffer as it downloads (syntax highlighted if appropriate), so you can be editing the beginning of a large file while the rest of it downloads.

Saving a file in such a buffer, or writing a buffer to a file name that starts with ftp://, will cause Epsilon to send the file to the remote computer. Upload and download status is indicated in the mode line, and there's also a show-connections command (on Ctrl-Alt-c) that shows the status of all Internet activities and buffers. As in bufed, you can select a buffer and press <Enter> to switch to it, or press <Escape> to remain in the current buffer. Use the kill-process command to cancel an FTP transfer or Telnet session (see below) in progress in the current buffer.

FTP and SCP URLs (the latter described in the next section) work with dired also, so if you do a dired (or a find-file) on ftp://user@example.com, you'll get a directory listing of the files on the remote machine example.com, in a familiar dired context. Dired knows how to delete and rename remote files, and sort by size, date, file name or extension. To make Epsilon work with certain host computers (systems running VMS, for example), you may need to set the variables ftp-ascii-transfers or ftp-compatible-dirs ; see the descriptions of those variables in the online help. Other systems may require you to set the variable ftp-passive-transfers .

The telnet command lets you connect to a command shell on a remote computer. The ssh command described in the next section provides the secure equivalent. Each creates a buffer that works much like the Epsilon process buffer, except the commands you type are executed on the remote machine. Provide a numeric prefix argument and telnet will connect on the specified port instead of the default port. Or use the syntax hostname:port for the host name to specify a different port. You can either use the telnet command directly, or specify a telnet: URL to find-file. (Epsilon ignores any username or password included in the URL.) Typing Ctrl-c Ctrl-c in telnet or ssh buffers sends an interrupt signal to the remote system, aborting the current program.

In a telnet buffer, the telnet-interpret-output variable controls whether Epsilon interprets certain ANSI color-setting escape sequences and similar things. (The ssh-interpret-output variable is the equivalent for ssh.) Epsilon also looks for password requests from the remote system, using the recognize-password-pattern variable, so it can hide the password as you type it. Also see the recognize-password-prompt variable, and the send-invisible command.

Normally Epsilon doesn't send a line in a telnet or ssh buffer until you press <Enter>. Type Ctrl-u <Enter> to send a partial line immediately.

As in a concurrent process buffer, you can press Alt-p or Alt-n to access a telnet or ssh buffer's command history. With a numeric prefix argument, these keys show a menu of all previous commands. You can select one to repeat.

If you specify an http: URL to find-file (for example, http://www.lugaru.com), Epsilon will use the HTTP protocol to retrieve the HTML code from the given location. The HTML code will appear in an appropriately named buffer, syntax highlighted. Header information for the URL will be appended to a buffer named "HTTP Headers".

You can tell Epsilon to send its requests by way of a proxy by setting the variables http-proxy-server, http-proxy-port, and http-proxy-exceptions. You can tell Epsilon to identify itself to the server as a different program by setting http-user-agent, or set http-force-headers to entirely replace Epsilon's HTTP request with another, or to add other headers. The http-log-request variable makes Epsilon copy the entire request it sends to the HTTP Headers buffer.

If you specify an https: URL to find-file, Epsilon will try to run the curl or wget programs, if they are installed, to retrieve the URL's contents and insert it in an appropriately-named buffer. Windows users can install either of these programs via the Cygwin system. Mac OS systems typically have curl installed by default, but users can install either via the Homebrew system if necessary. Linux and FreeBSD users can install via their system's package installers.

The Alt-e and Alt-<Down> keys in find-file come in handy when you want to follow links in an HTML buffer; see Command History for information on Alt-e and Completion & Defaults for information on Alt-<Down>. Also see the find-linked-file command on Ctrl-x Ctrl-l.

The command view-web-site on Shift-F8 searches for the next URL in the buffer. It prompts with that URL, and after you modify it if necessary, it then launches an external browser on the URL. The view-lugaru-web-site command launches a browser and points it to Lugaru's web site. Epsilon for Unix uses a shell script named goto_url to run a browser. See Web-based Epsilon Documentation. Epsilon for Windows uses the system's default browser.

If you run a compiler via telnet or a similar process in an Epsilon buffer, you can set up the next-error command on Ctrl-x Ctrl-n so that when it parses a file name in an error message, it translates it into a URL-style file name that Epsilon can use to access the file. To do this, you'll need to write your own telnet_error_converter() subroutine in EEL. See the sample one in the Epsilon source file epsnet.e for details.

Standard bindings:

Ctrl-Alt-c    show-connections

Telnet mode only: Alt-n    process-next-cmd

Telnet mode only: Alt-p    process-previous-cmd

   telnet

   telnet-mode

   view-web-site

   view-lugaru-web-site

Subtopics:

Secure Shell and SCP Support
URL Syntax

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