Prompt for iPhone and iPad

If you’re like me, you run virtual servers at data centers across the United States, and might need to log in suddenly when an outage occurs as you’re flying on a Wi-Fi-enabled plane between Seattle and JFK. No? You’re not like me? So long as you regularly need to make an SSH terminal connection on an iPad, you still might find Prompt worthwhile.

Those of us who sometimes or frequently don a system administrator mantle and type in instructions at a command-line prompt were pleased when terminal-emulation programs appeared in the very first wave of iOS apps three years ago. I never had a favorite, however, until Panic introduced Prompt. Panic is known for bundling complicated technical tasks into simple packages on the Mac, and Prompt delivers the same for using a terminal in iOS.

The $8 app provides VT100 emulation including support for color. That means when I fire up vim to do some screen-based edit—please, no emacs bigots here—the syntax-based hues in my files work just as well as they do in OS X’s Terminal app. Prompt has no bells nor whistles, unless you count the virtual beep option in its Settings menu, which flashes the screen instead of an audio retort.

The connection option is where most of the complexity lives, and Panic could clear this up with a little better elaboration. The normal entry fields for Server, Username, and Password make sense, as does the option of leaving the Password field empty in order to be prompted on each connection for the key to the castle instead of storing it.

When you add SSH key pairs for password-free connections, however, it gets more complicated. Prompt requires that you give it access to the RSA or DSA private key in a public-private pair generated by a program like ssh-keygen at the command line. (You also have to have the public key in that pair stored on the machine you want to connect to. Here’s a quick how-to for CentOS Linux.)

Unfortunately, Panic’s Prompt FAQ doesn’t provide full step-by-step directions and has no illustrations on how to make the private key available. The user interface lacks enough feedback, perhaps in the interests of simplicity. Keys may be imported either through the iOS clipboard or via iTunes using the File Sharing features in the Apps tab with a device connected. But one must open the key in another iOS app and copy it to make it available for import, or have access to a computer on which you can save the key as text and connect with iTunes.

Panic could make this easier by tying into Dropbox, or allowing an SSL connection over HTTP to a website location you provide, among other methods. Further, keys imported via the clipboard are named Imported Key, Imported Key 1, and so on—there’s no way to rename these, although you can delete keys.

Once you connect, the configuration is automatically added to the Connections list. Active connections are shown with an Eject icon next to them; click to force a disconnect. Connections are maintained in the background when the app isn’t running, unless your network connection changes, such as roaming between 3G and Wi-Fi.

You can use the touch keyboard or an external dock or Bluetooth keyboard to type, and use either landscape or portrait orientation. Prompt makes available four custom keys that can be reset to common single-character shortcuts at the top. Escape, Control, and Tab buttons are also available when using the touchscreen keyboard. Arrow keys and function keys are also available. Prompt also optionally keeps track of frequently entered commands and offers them as auto-fill options which expand in quantity over time. (There’s no way to sync these between iOS devices, which would be nice.)

Prompt meets the task, but needs a bit of improvement to be the perfect simple terminal tool. Still, even with the rough edges calling out for improvement, it remains my favorite terminal app for iOS devices.

[Glenn Fleishman, a senior contributor to Macworld, cut his teeth with paper tape and 110-baud real terminals in 1981. He writes regularly about networking and security.]