From 80076cd9ddfc5dae907ac10f3010925f181b028e Mon Sep 17 00:00:00 2001
From: Tom Ryder <tom@sanctum.geek.nz>
Date: Sun, 21 Aug 2016 20:44:39 +1200
Subject: Restructure ed() to test,cache features on login

---
 sh/profile.d/ed.sh | 22 ++++++++++++++++++++++
 sh/shrc.d/ed.sh    | 38 ++++++++++++++++++--------------------
 2 files changed, 40 insertions(+), 20 deletions(-)
 create mode 100644 sh/profile.d/ed.sh

diff --git a/sh/profile.d/ed.sh b/sh/profile.d/ed.sh
new file mode 100644
index 00000000..abbd75c5
--- /dev/null
+++ b/sh/profile.d/ed.sh
@@ -0,0 +1,22 @@
+# Test that we have metadata about what options this system's ed(1) supports,
+# and try to create it if not
+(
+    # Create a directory to hold metadata about ed
+    ecd=$HOME/.cache/ed
+    if ! [ -d "$ecd" ] ; then
+        mkdir -p -- "$ecd" || exit
+    fi
+
+    # Write ed(1)'s --help output to a file, even if it's empty
+    if ! [ -f "$ecd"/help ] ; then
+        ed --help </dev/null >"$ecd"/help 2>/dev/null || exit
+
+        # Iterate through some useful options and create files to show they're
+        # available
+        set -- verbose
+        for opt ; do
+            grep -q -- --"$opt" "$ecd"/help || continue
+            touch -- "$ecd"/"$opt" || exit
+        done
+    fi
+)
diff --git a/sh/shrc.d/ed.sh b/sh/shrc.d/ed.sh
index 4638d2cb..243dcffc 100644
--- a/sh/shrc.d/ed.sh
+++ b/sh/shrc.d/ed.sh
@@ -1,26 +1,24 @@
-# Add a colon prompt to ed when a command is expected rather than text; makes
-# it feel a lot more like using ex. Only do this when stdin is a terminal,
-# however. Also try and use -v for more verbose error output, and rlwrap(1) if
-# it's available.
+# Define function proper
 ed() {
 
-    # We're only adding options if input is from a terminal
-    if [ -t 0 ] ; then
+    # Don't mess with original call if input not a terminal
+    if ! [ -t 0 ] ; then
+        command ed "$@"
+        return
+    fi
 
-        # Colon prompt (POSIX)
-        set -- -p : "$@"
+    # Add --verbose to explain errors
+    [ -e "$HOME"/.cache/ed/verbose ] &&
+        set -- --verbose "$@"
 
-        # Verbose if available (not POSIX)
-        if ed -sv - </dev/null >&0 2>&0 ; then
-            set -- -v "$@"
-        fi
-    fi
+    # Add a colon prompt (POSIX feature)
+    set -- -p: "$@"
 
-    # Execute the ed(1) call, in a wrapper if appropriate and with the
-    # concluded options
-    if [ -t 0 ] && command -v rlwrap >/dev/null 2>&1 ; then
-        command rlwrap ed "$@"
-    else
-        command ed "$@"
-    fi
+    # Run in rlwrap(1) if available
+    set -- ed "$@"
+    command -v rlwrap >/dev/null 2>&1 &&
+        set -- rlwrap "$@"
+
+    # Run determined command
+    command "$@"
 }
-- 
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