Add fixnl() to fix common newline-related annoyances

dotfiles/bash/main.bashrc

@@ -102,6 +102,48 @@ vims() {
       | tac
 }
 
+fixnl() {
+    #
+    # Fix newlines in stdin and pass to stdout
+    #
+    # Note: We need to read whole stdin; this cannot work
+    # for infinite stream.
+    #
+    # Fix annoying cases:
+    #
+    #  *  If multi-line text is missing newline at the
+    #     end---add the missing newline.
+    #
+    #  *  If -c is passed, and single-line text does have
+    #     a newline at the end, remove it.
+    #
+    # This will not touch properly terminated multi-line texts,
+    # or zero-line texts (ie. oly chars with no newline at all).
+    #
+    local arg=$1        # argument passed
+    local cache         # cache to keep stream in
+    local nlcount       # count of newlines in the stream
+    local lastchr       # hex dump (2-digit, lowercase) of last char
+    local single=keep   # single-line streams:
+                        #   keep: do nothing
+                        #   chop: drop last char if it's a LF
+    case $arg in
+        -c|--chop-single) single=chop ;;
+    esac
+    cache="$(mktemp -t fixnl.XXXXXXXX)"
+    cat >"$cache"
+    nlcount=$(<"$cache" wc -l)
+    lastchr=$(<"$cache" tail -c1 | hexdump -e '"%02x"')
+    case $nlcount:$lastchr:$single in
+        0:??:*)     cat "$cache"        ;;  # 'abc'       => keep as is
+        1:0a:chop)  head -c -1 "$cache" ;;  # 'abc\n'     => -c passed: chop!
+        1:0a:keep)  cat "$cache"        ;;  # 'abc\n'     => keep as is
+        *:0a:*)     cat "$cache"        ;;  # 'a\nb\nc\n' => keep as is
+        *:??:*)     cat "$cache";  echo ;;  # 'a\nb\nc'   => add the missing NL
+    esac
+    rm "$cache"
+}
+
 xod() {
     #
     # Like mktemp but get the content from clipboard