When pressing an unbound key or key combination in bash and other readline programs, somewhat cryptic characters are often inserted into the command line. For example, you get "~" for Insert, "4~" for F12, or ";5A" for Ctrl+Up. This can be rather confusing and annoying.
The reason is that readline does not parse control sequences as defined in section 5.4 of the ECMA-48 standard correctly. VT100 terminals and its numerous descendants use those for many keys or key combinations that don't have single-character codes. They start with the control sequence introducer (CSI), normally represented by "\e[", followed by parameter and intermediate bytes in the range from 0x20 to 0x3F, followed by a final byte in the range from 0x40 to 0x7E. Readline, at least in its default config, stops parsing these sequences after the first byte following the "\e[", leaving any remaining bytes to spill onto the command line. As far as I can see, there's currently no way to address this short of explicitly binding all the CSI keycodes to nothing. (Well, actually, a single binding seems to suffice for codes that differ only in the last character, but that doesn't help with the F-keys and the likes of Insert.) That's a rather long list though, which would slow down startup and lead to an explosion in the number of keymaps allocated internally by readline. Hence the attached small patch for the readline source, which avoids such inefficiencies. It defines a function called 'skip-csi-seq' that skips over the parameter, intermediate, and final bytes. This is assigned to '\e['. Generally in readline, bindings for longer sequences take precedence over shorter ones, which ensures that CSI sequences that do have functions bound to them continue to work. Here's the result in the output of 'bind': $ bind -p | grep e\\[ "\e[D": backward-char "\e[H": beginning-of-line "\e[3~": delete-char "\e[F": end-of-line "\e[C": forward-char "\e[B": next-history "\e[A": previous-history "\e[": skip-csi-seq It's working correctly here, including when adding bindings for longer keycodes: no more funny characters when accidentally hitting the wrong key. Please consider the patch for inclusion into the readline package. Regards, Andy
rl_skip_csi_seq.patch
Description: Binary data
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