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+# bash-scripts
+
+A collection of Bash utilities. Works on Linux, macOS, WSL, and Git Bash (Windows).
+
+## Scripts
+
+| Script | Purpose |
+|---|---|
+| [find_duplicate_pictures.sh](find_duplicate_pictures.sh) | Find duplicate pictures across one or more filesystems/directories using name **and** content comparison |
+
+---
+
+## find_duplicate_pictures.sh
+
+Finds all picture files and reports duplicates. Because more than one picture
+can legitimately share the same file name (e.g. `IMG_0001.jpg` from two
+different cameras), the script does **not** trust names alone — it combines
+three independent checks:
+
+1. **Same name** — groups files sharing the same file name (case-insensitive).
+   Fast, but only a hint.
+2. **Same content** *(authoritative)* — file size is used as a cheap
+   pre-filter, then SHA-256 hashes are computed **only for size-matched
+   candidates**. Identical hashes = true duplicates, regardless of name.
+   Also reports approximate disk space wasted by redundant copies.
+3. **"False friends"** — files with the *same name but different content*
+   (the exact case where names are misleading).
+
+### Usage
+
+```bash
+# Scan specific roots
+./find_duplicate_pictures.sh /home/user/Pictures /mnt/backup
+
+# Scan the whole filesystem (default when no arguments given)
+./find_duplicate_pictures.sh
+
+# On Windows (Git Bash) — drives are /c, /d, ...
+"/c/Program Files/Git/bin/bash.exe" find_duplicate_pictures.sh /c /d
+
+# Make it executable first if needed
+chmod +x find_duplicate_pictures.sh
+```
+
+### Options (environment variables)
+
+| Variable | Default | Description |
+|---|---|---|
+| `HASH_CMD` | auto-detected | Hash tool to use: `sha256sum`, `shasum -a 256`, or `md5sum` (last resort) |
+| `FOLLOW_LINKS` | `0` (off) | Set to `1` to follow symlinks while scanning |
+| `REPORT` | *(none)* | Path to a file where the full report is also saved |
+
+### Examples
+
+```bash
+# Save the report to a file
+REPORT=dupes.txt ./find_duplicate_pictures.sh ~/Pictures
+
+# Follow symlinks, scan two drives
+FOLLOW_LINKS=1 ./find_duplicate_pictures.sh /mnt/c /mnt/d
+
+# Force a specific hash tool
+HASH_CMD="shasum -a 256" ./find_duplicate_pictures.sh ~/Pictures
+```
+
+### Sample output
+
+```
+=== Step 1: scanning for picture files ===
+  -> /tmp/picdup_test
+  found 3 picture file(s)
+
+=== Step 2: duplicates by file name ===
+--- name: photo1.jpg ---
+         100 bytes  /tmp/picdup_test/a/photo1.jpg
+         120 bytes  /tmp/picdup_test/b/photo1.jpg
+  1 name group(s) share the same file name
+
+=== Step 3: duplicates by content (SHA-256) ===
+  hashing 2 candidate file(s) with matching sizes...
+--- identical content (sha256: 57e8310931615cb7...) ---
+         100 bytes  /tmp/picdup_test/a/photo1.jpg
+         100 bytes  /tmp/picdup_test/b/copy_of_photo1.jpg
+  1 content group(s) are true duplicates
+  approx. space wasted by extra copies: 100 bytes (100)
+
+=== Step 4: same name, different content (false friends) ===
+--- 'photo1.jpg' is used by 2 DIFFERENT pictures: ---
+  [57e831093161] /tmp/picdup_test/a/photo1.jpg
+  [unique-size] /tmp/picdup_test/b/photo1.jpg
+```
+
+### Supported image formats
+
+`jpg`, `jpeg`, `png`, `gif`, `bmp`, `tiff`, `tif`, `webp`, `heic`, `heif`,
+`svg`, `ico`, `raw`, `cr2`, `nef`, `arw`, `dng`, `psd`, `avif`, `jfif`
+
+Matching is case-insensitive (`.JPG`, `.Jpg`, … all match). To change the
+list, edit the `EXTENSIONS` variable at the top of the script.
+
+### Notes & limitations
+
+- **Safety:** the script is read-only — it never deletes or modifies files.
+- **Skipped paths:** `/proc`, `/sys`, `/dev`, `/run`, `/snap`, `/tmp` are
+  pruned during full-system scans (edit `PRUNE_DIRS` to change).
+- **Performance:** only files whose size appears more than once are hashed,
+  which keeps large collections fast. Whole-filesystem scans still take time.
+- **Filenames:** names with spaces, tabs, or other special characters are
+  handled correctly (NUL-delimited scanning).
+- **Permissions:** unreadable files/directories are skipped silently.
+- **Exit codes:** `0` on success; `1` if no hashing tool is available or the
+  temp directory cannot be created.
+
+### Requirements
+
+- Bash 4+ (for `mapfile`)
+- One of: `sha256sum`, `shasum`, or `md5sum`
+- Standard tools: `find`, `awk`, `sort`, `stat`, `cut`, `grep`, `wc`
+  (all present on Linux/macOS/Git Bash/WSL)