diff --git a/README.md b/README.md
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index e0b8e82..0000000
--- a/README.md
+++ /dev/null
@@ -1,3 +0,0 @@
-# rename-ext
-
-changes file-extension based on mime-type
\ No newline at end of file
diff --git a/install.sh b/install.sh
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index 0000000..d331987
--- /dev/null
+++ b/install.sh
@@ -0,0 +1,12 @@
+#!/bin/bash
+
+# rename-ext install script
+
+PREFIX=~/.local
+
+git clone --depth 1 \
+  'https://source.garden/dym/rename-ext.git' \
+  $PREFIX/src/rename-ext/
+
+ln -s $PREFIX/src/rename-ext/rename-ext.sh \
+      $PREFIX/bin/rename-ext
diff --git a/meta.kdl b/meta.kdl
new file mode 100644
index 0000000..60e8fc7
--- /dev/null
+++ b/meta.kdl
@@ -0,0 +1,7 @@
+title        "rename-ext"
+description  "changes file-extension based on mime-type"
+type         "code"
+tags         "script"  "bash"  "file-management"
+license      "AGPL"
+homepage     "https://dym.sh/rename-ext"
+source       "https://source.garden/dym/rename-ext"
diff --git a/readme.md b/readme.md
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index 0000000..9d3f21c
--- /dev/null
+++ b/readme.md
@@ -0,0 +1,51 @@
+# rename-ext
+
+> changes file-extension based on mime-type
+
+### also
+
+- removes `*?|^:"<>` characters from the file-name
+- reducing multiple spaces, dots, and underscores
+- adds rename-date suffix to ensure uniquness of the filename
+- strips exec-flag from non-executive types (usual leftover from FAT/NTFS)
+- optimizes images while at it (shows reduction size in `kb` and `%`)
+
+
+## install
+
+1. look at [install](./install.sh) file for instructions
+2. adjust `PREFIX` at wish
+3. make sure the final directory is on `$PATH`
+
+
+## use
+
+`rename-ext /Data/Pictures/_unsorted/**/*`
+
+to only change extension and nothing else:
+
+`rename-ext --only-ext /Data/Photos/2020/*`
+
+to only print a report:
+
+`rename-ext --test-run /Data/Docs/_dump/*`
+
+
+## requires
+
+- [`sd`](https://github.com/chmln/sd) – better sed
+- [`pngcrush`](https://github.com/Kjuly/pngcrush) – to compress PNGs
+<!-- - [`pngquant`](https://github.com/kornelski/pngquant) – to compress PNGs -->
+- [`jpegoptim`](https://github.com/tjko/jpegoptim) – to compress JPEGs
+
+
+## todo
+- [ ] find better determination tool for `application/octet-stream`
+- [ ] leverage `fd` to do recursive paralel execution if some of parameters are folders
+
+
+## q&a
+
+**Q**: why not just rename files to hashes of their contents, and store original filenames in some database?
+
+**A**: good point. that database is in my case a filesystem itself.
diff --git a/rename-ext.sh b/rename-ext.sh
new file mode 100755
index 0000000..8d32014
--- /dev/null
+++ b/rename-ext.sh
@@ -0,0 +1,311 @@
+#!/bin/bash
+
+## rename-ext
+# > changes file-extension based on mime-type
+
+## also
+# - removes `*?|^:"<>` characters from the file-name
+# - reducing multiple spaces, dots, and underscores
+# - adds rename-date suffix to ensure uniquness of the filename
+# - strips exec-flag from non-executive types (usual leftover from FAT/NTFS)
+# - optimizes images while at it (shows reduction size in `kb` and `%`)
+
+## example
+# rename-ext /Data/Pictures/_unsorted/**/*
+
+## requires
+# - `cargo install sd` – better sed
+# - pngcrush – to compress PNGs (losless)
+# // - pngquant – to compress PNGs (lossy)
+# - jpegoptim – to compress JPEGs
+
+
+ALL_EXTS=`echo \
+  'gif|jpe?g|jp2|jfif|a?png|web(p|m)|svg
+  |eps|tga|tiff?|psd|ico|xcf|heic
+  |eot|otf|ttf|epub|doc|docx|xls|swf|pdf|odt
+  |flac|opus|ogg|m4a|wav
+  |mpe?g|mp\d|mov|mkv|avif?|asf|3gpp?
+  |html?|sh|py|php
+  ' \
+  |  tr -d '[:space:]' \
+  `
+
+mkdir -p ~/tmp
+
+
+OPTIONS=''
+CHX_CHANGELOG=''
+NR='1'
+
+
+calc_reduction()
+{
+  SIZE_PRE="$1"
+  SIZE_POST="$2"
+  PERECENT=` echo "scale=2; 100 - (100 * $SIZE_POST / $SIZE_PRE)" | bc `
+  RESULT="$(( $SIZE_PRE / 1000 ))-$(( ( $SIZE_PRE - $SIZE_POST ) / 1000 )) kb \
+($PERECENT%)
+"
+  echo "$RESULT"
+}
+
+
+ch_x()
+{
+  FILENAME="$1"
+  # echo "FILENAME = '$FILENAME'"
+
+  CHX_CHANGELOG=''
+
+  IS_X_INTENDED='0'
+  if [ ! -z "$2" ]; then
+    IS_X_INTENDED='1'
+  fi
+  # echo "IS_X_INTENDED = '$IS_X_INTENDED'"
+
+  IS_X=`stat -c '%A' "$FILENAME" | grep 'x' | wc -l`
+  # echo "IS_X = '$IS_X'"
+
+  MODE='-x'
+  if [[ '1' == "$IS_X_INTENDED" ]]; then
+    MODE='+x'
+  fi
+  # echo "MODE = '$MODE'"
+
+  if [[ ! "$OPTIONS" =~ 'test-run' ]]; then
+    # echo '(not a test-run)'
+    if [[ ! "$OPTIONS" =~ 'only-ext' ]]; then
+      # echo '(not only-ext)'
+      if [[ ! "$IS_X" == "$IS_X_INTENDED" ]]; then
+        CHX_CHANGELOG="chmod $MODE"
+      fi
+      chmod "$MODE" "$FILENAME"
+    fi
+  fi
+}
+
+
+rename_ext()
+{
+  NAME="$1"
+  EXT="$2"
+  NOTE=''
+  TARGET=''
+
+  ch_x "$FILENAME"
+
+  if [[ "$OPTIONS" =~ 'only-ext' ]]; then
+    NAME_NO_EXT=` echo "$NAME" \
+                | sd -f i "(\.+($ALL_EXTS))$" '' \
+                `
+    TARGET="$NAME_NO_EXT.$EXT"
+  else
+    if [[ ! "$OPTIONS" =~ 'test-run' ]]; then
+
+      SIZE_PRE=` stat "$FILENAME" -c '%s' `
+
+      [ 'jpg' = "$EXT" ] \
+        && jpegoptim "$FILENAME" -qsftp
+      if [ 'png' = "$EXT" ]; then
+        mogrify "$FILENAME"
+        pngcrush -nolimits -s "$FILENAME" "$FILENAME.tmp.png"
+        # pngquant "$FILENAME" --output "$FILENAME" \
+        #   --quality=100 --force --skip-if-larger --speed 1
+        if [ -f "$FILENAME.tmp.png" ] \
+          && [ -s "$FILENAME.tmp.png" ]
+        then
+          mv "$FILENAME.tmp.png" "$FILENAME"
+        else
+          rm "$FILENAME.tmp.png"
+        fi
+      fi
+
+      SIZE_POST=` stat "$FILENAME" -c '%s' `
+
+      [ $SIZE_PRE -gt $SIZE_POST ] \
+        && NOTE=` calc_reduction "$SIZE_PRE" "$SIZE_POST" `
+    fi
+    DATE=` date -r "$NAME" -u "+%Y%m%d%H%M%S" `
+    TCLEAN=` echo "$NAME" \
+           | sd '[\\\?\*\|^:"<>]+' '_' \
+           | sd '_\d{12,}\.' '.' \
+           | sd -f i "(\.+($ALL_EXTS))+$" '' \
+           `
+    TARGET=` echo "${TCLEAN}_$DATE.$EXT" \
+          | sd '([\s\.,_]){3,}' '$1' \
+          `
+  fi
+
+  IS_SAME_NAME='0'
+  if [[ "$NAME" == "$TARGET" ]]; then
+    IS_SAME_NAME='1'
+  fi
+  # echo "IS_SAME_NAME = '$IS_SAME_NAME'"
+
+  # echo "CHX_CHANGELOG = '$CHX_CHANGELOG'"
+  if [[ '1' == "$IS_SAME_NAME" ]] \
+    && [ -z "$CHX_CHANGELOG" ]
+  then
+    return
+  fi
+
+  echo "$NR:"
+  NR="$(($NR+1))"
+  echo "  $FILENAME"
+
+  if [ ! -z "$CHX_CHANGELOG" ]; then
+    echo "  $CHX_CHANGELOG"
+    CHX_CHANGELOG=''
+  fi
+
+  if [[ '1' == "$IS_SAME_NAME" ]]; then
+    return
+  fi
+
+
+  if [[ "$OPTIONS" =~ 'test-run' ]]; then
+    if [ -f "$TARGET" ]; then
+      if [[ "$PARAMS" =~ 'force-replace' ]]; then
+        echo "  >> replacing existing file >>"
+      else
+        echo "  !! file already exist !!"
+      fi
+    fi
+    echo "$TARGET"
+  else
+    if [ ! -f "$TARGET" ]; then
+      echo "  >> $NOTE >>"
+      echo "  $TARGET"
+      mv "$NAME" "$TARGET"
+    else
+      if [[ "$PARAMS" =~ 'force-replace' ]]; then
+        echo "  >> $NOTE ## replacing existing file >>"
+        echo "  $TARGET"
+        mv "$NAME" "$TARGET"
+      else
+        echo '  !! File already exist, use `--force-replace` to overwrite !! '
+        echo "  $TARGET"
+      fi
+    fi
+  fi
+
+}
+
+for PARAM in "$@"; do
+  # echo "PARAM = '$PARAM'"
+  if [[ '--only-ext' == "$PARAM" ]]; then
+    OPTIONS="$OPTIONS;only-ext"
+    # echo "OPTIONS = '$OPTIONS'"
+  elif [[ '--test-run' == "$PARAM" ]]; then
+    OPTIONS="$OPTIONS;test-run"
+    # echo "OPTIONS = '$OPTIONS'"
+  elif [[ '--force-replace' == "$PARAM" ]]; then
+    OPTIONS="$OPTIONS;force-replace"
+    # echo "OPTIONS = '$OPTIONS'"
+  fi
+done
+
+[ ! -z "$OPTIONS" ] \
+  && echo "OPTIONS: '$OPTIONS'"
+
+
+# echo "@ = '$@'"
+for FILENAME in "$@"; do
+
+  # echo "FILENAME = '$FILENAME'"
+
+  # NOT_F_=`[ ! -f "$FILENAME" ]`
+  # echo "NOT_F_ = '$NOT_F_'"
+
+  # [ ! -f "$FILENAME" ] \
+  #   && continue
+
+  FILE_TYPE=` file -b --mime-type "$FILENAME" `
+  # echo "FILE_TYPE = '$FILE_TYPE'"
+
+  case "$FILE_TYPE" in
+
+  # pixel-based
+  'image/gif') rename_ext "$FILENAME" 'gif' ;;
+  'image/jpeg') rename_ext "$FILENAME" 'jpg' ;;
+  'image/jp2') rename_ext "$FILENAME" 'jp2' ;;
+  'image/png') rename_ext "$FILENAME" 'png' ;;
+  'image/webp') rename_ext "$FILENAME" 'webp' ;;
+
+  # vector-based
+  'image/svg+xml') rename_ext "$FILENAME" 'svg' ;;
+  'image/x-eps') rename_ext "$FILENAME" 'eps' ;;
+
+  # some less common image formats
+  'image/heic') rename_ext "$FILENAME" 'heic' ;;
+  'image/tiff') rename_ext "$FILENAME" 'tiff' ;;
+  'image/vnd.adobe.photoshop') rename_ext "$FILENAME" 'psd' ;;
+  'image/vnd.microsoft.icon') rename_ext "$FILENAME" 'ico' ;;
+  'image/x-tga') rename_ext "$FILENAME" 'tga' ;;
+  'image/x-xcf') rename_ext "$FILENAME" 'xcf' ;;
+
+  # fonts
+  'application/vnd.ms-fontobject') rename_ext "$FILENAME" 'eot' ;;
+  'application/vnd.ms-opentype') rename_ext "$FILENAME" 'otf' ;;
+  'font/sfnt') rename_ext "$FILENAME" 'ttf' ;;
+
+  # documents
+  'application/epub+zip') rename_ext "$FILENAME" 'epub' ;;
+  'application/msword') rename_ext "$FILENAME" 'doc' ;;
+  'application/pdf') ch_x "$FILENAME" ;;  # can be .ai
+  'application/vnd.ms-excel') rename_ext "$FILENAME" 'xls' ;;
+  'application/vnd.oasis.opendocument.text') rename_ext "$FILENAME" 'odt' ;;
+  'application/vnd.openxmlformats-officedocument.wordprocessingml.document') rename_ext "$FILENAME" 'docx' ;;
+  'application/x-shockwave-flash') rename_ext "$FILENAME" 'swf' ;;
+
+  # audio
+  'audio/flac') rename_ext "$FILENAME" 'flac' ;;
+  'audio/mpeg') rename_ext "$FILENAME" 'mp3' ;;
+  'audio/ogg') rename_ext "$FILENAME" 'ogg' ;;
+  'audio/x-m4a') rename_ext "$FILENAME" 'm4a' ;;
+  'audio/x-wav') rename_ext "$FILENAME" 'wav' ;;
+
+  # video
+  'video/3gpp') rename_ext "$FILENAME" '3gp' ;;
+  'video/av1') rename_ext "$FILENAME" 'avi' ;;
+  'video/MP2T') rename_ext "$FILENAME" 'mp2' ;;
+  'video/mp4') rename_ext "$FILENAME" 'mp4' ;;
+  'video/quicktime') rename_ext "$FILENAME" 'mov' ;;
+  'video/webm') rename_ext "$FILENAME" 'webm' ;;
+  'video/x-m4v') rename_ext "$FILENAME" 'mp4' ;;
+  'video/x-matroska') rename_ext "$FILENAME" 'mkv' ;;
+  'video/x-ms-asf') rename_ext "$FILENAME" 'asf' ;;
+
+  # text
+  'application/json') ch_x "$FILENAME" ;;  # can be any other language
+  'text/html') ch_x "$FILENAME" ;;  # can be .htm, .htc, .mht, ...
+  'text/xml') ch_x "$FILENAME" ;;  # can be .xml, .opml, .rss, ...
+  'text/plain') ;;  # can be any file with not enough text
+  'text/x-python') ;;  # can be .py, .py3, have no .ext
+  'text/x-shellscript') ;;  # can be .sh, .zsh, have no .ext
+
+  # binady data
+  'application/x-sqlite3') ch_x "$FILENAME" ;;  # can be .db, .sql, .sq3
+
+  # special
+  'application/octet-stream') ;;  # can be anything
+  'inode/directory')
+    # echo "$FILENAME is a folder"
+    # echo "about to ch_x"
+    ch_x "$FILENAME" '+'
+    ;;  # a folder
+  'inode/x-empty') ch_x "$FILENAME" ;;  # zero-size
+
+  # default
+  *) echo "??  $FILENAME : $FILE_TYPE" ;;
+
+  esac
+
+done
+
+# if [[ "@#" -eq 1 ]]; then
+#   if [[ `file -b --mime-type "$1"` == "inode/directory" ]]; then
+#     find "$1"
+#   fi
+# fi