Update docs

4 files changed, 35 insertions, 22 deletions

diff --git a/README.md b/README.md
index 206bf80..3b07b03 100644
--- a/README.md
+++ b/README.md
@@ -194,7 +194,7 @@ Option completion scripts for Bash, Fish and Zsh can be found in respective subd
 
 1. Install the [utilities required](#utility-dependencies) for your regular activities.
 2. Configure [cd on quit](https://github.com/jarun/nnn/wiki/hacking-nnn#cd-on-quit).
-3. Optionally open all text files in EDITOR (fallback vi): `export NNN_USE_EDITOR=1`
+3. Optionally open all text files in `$EDITOR` (fallback vi): `export NNN_USE_EDITOR=1`
 4. Run `n`.
 5. To use `nnn` as a GUI app launcher with fuzzy selection menu, drop [`nlaunch`](https://github.com/jarun/nnn/blob/master/user-scripts/nlaunch) somewhere in your `$PATH`.
 6. Don't memorize keys. Arrows, <kbd>/</kbd> and <kbd>q</kbd> suffice. Press <kbd>?</kbd> for help on keyboard shortcuts anytime.
diff --git a/user-scripts/README.md b/user-scripts/README.md
index 14fc0e5..5b481c3 100644
--- a/user-scripts/README.md
+++ b/user-scripts/README.md
@@ -1,18 +1,31 @@
-| Script (a-z) | Description |
-| --- | --- |
-| copier | Copy selection to clipboard |
-| edit | Fuzzy find a file in directory subtree with fzy and edit in vim |
-| fzy | Fuzzy find a file in directory subtree with fzy and open using xdg-open |
-| hexview | view a file in hex; needs xxd and $PAGER |
-| imgresize | Resize images in directory to screen resolution (needs [imgp](https://github.com/jarun/imgp)) |
-| imgur | Upload an image file to imgur |
-| kdeconnect | Send selected files to Android device using kdeconnect-cli |
-| ndiff | File and directory diff for selection using vimdiff |
-| nlaunch | Drop-down independent app launcher (needs fzy), drop in `$PATH`; fallback regular prompt |
-| nwal | Set the selected image as wallpaper using nitrogen |
-| paste | Paste contents of current (text) file to paste.ubuntu.com (needs [pastebinit](https://launchpad.net/pastebinit)) |
-| picker | Pick files and pipe the newline-separated list to another utility |
-| pywal | Set the selected image as wallpaper using pywal and change the terminal color schemes |
-| sxiv | Open images in current directory in sxiv |
-| transfer | Upload current file to transfer.sh |
-| upgrade | Check and update to latest version of nnn manually on Debian 9 Stretch |
+| Script (a-z) | Lang | Deps | Description |
+| --- | --- | --- | --- |
+| copier | sh | OS-specific | Copy selection to clipboard |
+| edit | sh | fzy | Fuzzy find a file in directory subtree and edit in vim |
+| fzy | sh | fzy | Fuzzy find a file in directory subtree and open using xdg-open |
+| hexview | sh | xxd, $PAGER | view a file in hex |
+| imgresize | sh | [imgp](https://github.com/jarun/imgp) | Resize images in directory to screen resolution |
+| imgur | bash | [imgur](https://github.com/jomo/imgur-screenshot) | Upload an image to imgur |
+| kdeconnect | sh | kdeconnect-cli | Send selected files to an Android device |
+| ndiff | sh | vimdiff | File and directory diff for selection |
+| nlaunch | sh | fzy | Drop-down app launcher. Copy in `$PATH`; fallback regular prompt |
+| nwal | sh | nitrogen | Set the selected image as wallpaper using nitrogen |
+| paste | sh | [pastebinit](https://launchpad.net/pastebinit) | Paste contents of current (text) file to paste.ubuntu.com |
+| picker | sh | nnn | Pick files and pipe the newline-separated list to another utility |
+| pywal | sh | pywal | Set selected image as wallpaper, change terminal color scheme |
+| sxiv | sh | sxiv | Open images in a dir in sxiv, set wallpaper, copy path ([tips](https://wiki.archlinux.org/index.php/Sxiv#Assigning_keyboard_shortcuts))|
+| transfer | sh | curl | Upload current file to transfer.sh |
+| upgrade | sh | wget | Upgrade to latest nnn version manually on Debian 9 Stretch |
+
+### File access from scripts
+
+The design is flexible so a script can access:
+- all files in the directory (`nnn` switches to the dir where the script is to be run so the dir is `$PWD` for the script)
+- the currently highlighted file (the file name is passed as the first argument to a script)
+- the current selection (by reading the file .nnncp, see the script `copier`)
+
+### Contributing scripts
+
+All scripting languages should work. However, POSIX-compliant shell scripts runnable in `sh` are preferred. If that's too rudimentary for your use case, use Python, Perl or Ruby. Please keep non-portable commands (like `notify-send`) commented so users from any other OS/DE aren't surprised.
+
+The scripts should be executable. Please add an entry in the table above.
diff --git a/user-scripts/sxiv b/user-scripts/sxiv
index 985dce7..ef21cf7 100755
--- a/user-scripts/sxiv
+++ b/user-scripts/sxiv
@@ -2,7 +2,7 @@
 
 # Description: Open images in current directory in sxiv
 #
-# Shell: generic
+# Shell: POSIX compliant
 # Author: Arun Prakash Jana
 
 sxiv -q * >/dev/null 2>&1 &
diff --git a/user-scripts/upgrade b/user-scripts/upgrade
index 858a6a0..83b9949 100755
--- a/user-scripts/upgrade
+++ b/user-scripts/upgrade
@@ -1,8 +1,8 @@
-#!/usr/bin/env bash
+#!/usr/bin/env sh
 
 # Description: Check and update to latest version of nnn manually on Debian 9 Stretch
 #
-# Shell: bash
+# Shell: POSIX-compliant
 # Author: Arun Prakash Jana
 # NOTE: This script installs a package, should be issued with admin privilege