Idea for a Readline binding to increment/decrement a number

Want something similar to <C-a> and <C-x> in Vim. This function matches
and increments the number, but I'm currently stymied on how to insert
the number into the current line. There doesn't appear to be a way to do
that, except perhaps with the `shell-expand-line` function, and I don't
want to use that because I just want to insert the number, not expand
other parts of the shell line.

The other sticking point is how to read the value of the
`universal-argument`. There doesn't currently seem to be a way to do
that in a custom function.

I had a new idea for the number insertion problem, though. It's possible
I could replace the number, <C-c> the line, and reinsert a new copy with
the incremented/decremented number on the new shell line. That still
wouldn't resolve the `universal-argument` problem.

1 files changed, 21 insertions, 0 deletions

diff --git a/incdec b/incdec
new file mode 100644
index 0000000..15f4175
--- /dev/null
+++ b/incdec
@@ -0,0 +1,21 @@
+function incdec {
+	local EX_DATAERR=65
+
+	# Portion of the line from point to the end of the line.
+	local line_part="${READLINE_LINE:$READLINE_POINT}"
+
+	# Number to increment.
+	local number=
+
+	# If the line part doesn't contain a number, exit.
+	if ! [[ "$line_part" =~ ([0-9]+) ]]; then
+		return $EX_DATAERR
+	fi
+
+	number=${BASH_REMATCH[1]}
+
+	echo "$(($number + 1))"
+}
+
+# bind -x '"\C-xa+":incdec'
+# bind '"\C-xaa":\C-xa+'