diff_dirs - Quick directory comparison using rsync (bash/zsh/fish)

diff_dirs.bash

diff_dirs() {
  local group=0
  while [[ "$1" == -* ]]; do
    case "$1" in
      -g|--group) group=1; shift ;;
      -h|--help)
        echo "Usage: diff_dirs [-g] <folderA> <folderB>"
        echo ""
        echo "Quick directory comparison using rsync (compares by file size only)."
        echo ""
        echo "Options:"
        echo "  -g, --group  Group output by collapsing exclusive directories"
        echo ""
        echo "Output:"
        echo "  [ONLY in A]  - file exists only in folderA"
        echo "  [ONLY in B]  - file exists only in folderB"
        echo "  [CHANGED]    - file exists in both but differs"
        return 1
        ;;
      *) echo "Unknown option: $1"; return 1 ;;
    esac
  done

  if [[ $# -lt 2 ]]; then
    echo "Usage: diff_dirs [-g] <folderA> <folderB>"
    return 1
  fi

  local a="${1%/}" b="${2%/}"
  local nameA=$(basename "$a")
  local nameB=$(basename "$b")

  # If basenames are the same, use parent/basename
  if [[ "$nameA" == "$nameB" ]]; then
    nameA="$(basename "$(dirname "$a")")/$nameA"
    nameB="$(basename "$(dirname "$b")")/$nameB"
  fi

  if [[ $group -eq 1 ]]; then
    # Grouped output: collapse exclusive directories
    rsync -rin8 --size-only --delete "$a/" "$b/" | awk \
      -v labelA="$nameA" -v labelB="$nameB" '
      { lines[NR] = $0 }
      END {
        for (i = 1; i <= NR; i++) {
          line = lines[i]
          if (line ~ /^\*deleting +[^\/]+\/$/) {
            path = line; sub(/^\*deleting +/, "", path)
            excl_b[path] = 1
          }
          if (line ~ /^cd\+* +[^\/]+\/$/) {
            path = line; sub(/^[^ ]+ +/, "", path)
            excl_a[path] = 1
          }
        }
        for (i = 1; i <= NR; i++) {
          line = lines[i]
          if (line ~ /^\*deleting/) {
            path = line; sub(/^\*deleting +/, "", path)
            skip = 0
            for (d in excl_b) { if (path != d && index(path, d) == 1) skip = 1 }
            if (!skip) printf "[ONLY %-20s] %s\n", labelB, path
            continue
          }
          if (line ~ /^cd\+/) {
            path = line; sub(/^[^ ]+ +/, "", path)
            skip = 0
            for (d in excl_a) { if (path != d && index(path, d) == 1) skip = 1 }
            if (!skip) printf "[ONLY %-20s] %s\n", labelA, path
            continue
          }
          if (line ~ /^>f\+\+\+\+\+/) {
            path = line; sub(/^[^ ]+ +/, "", path)
            skip = 0
            for (d in excl_a) { if (index(path, d) == 1) skip = 1 }
            if (!skip) printf "[ONLY %-20s] %s\n", labelA, path
            continue
          }
          if (line ~ /^>f.s/) {
            path = line; sub(/^[^ ]+ +/, "", path)
            printf "[CHANGED%17s] %s\n", "", path
          }
        }
      }
    '
  else
    # Verbose output (default)
    rsync -rin8 --size-only --delete "$a/" "$b/" | awk \
      -v labelA="$nameA" -v labelB="$nameB" '
      /^\*deleting/   {sub(/^\*deleting +/, ""); printf "[ONLY %-20s] %s\n", labelB, $0; next}
      /^>f\+\+\+\+\+/ {sub(/^[^ ]+ +/, ""); printf "[ONLY %-20s] %s\n", labelA, $0; next}
      /^>f.s/         {sub(/^[^ ]+ +/, ""); printf "[CHANGED%17s] %s\n", "", $0}
    '
  fi
}

diff_dirs.fish

function diff_dirs -d "Quick directory comparison using rsync"
    argparse 'g/group' 'h/help' -- $argv
    or return 1

    if set -q _flag_help; or test (count $argv) -lt 2
        echo "Usage: diff_dirs [-g] <folderA> <folderB>"
        echo ""
        echo "Quick directory comparison using rsync (compares by file size only)."
        echo ""
        echo "Options:"
        echo "  -g, --group  Group output by collapsing exclusive directories"
        echo ""
        echo "Output:"
        echo "  [ONLY in A]  - file exists only in folderA"
        echo "  [ONLY in B]  - file exists only in folderB"
        echo "  [CHANGED]    - file exists in both but differs"
        return 1
    end

    set -l a (string trim -r -c "/" $argv[1])
    set -l b (string trim -r -c "/" $argv[2])
    set -l nameA (basename $a)
    set -l nameB (basename $b)

    # If basenames are the same, use parent/basename
    if test "$nameA" = "$nameB"
        set nameA (basename (dirname $a))/$nameA
        set nameB (basename (dirname $b))/$nameB
    end

    if set -q _flag_group
        # Grouped output: collapse exclusive directories
        rsync -rin8 --size-only --delete "$a/" "$b/" | awk \
            -v labelA="$nameA" -v labelB="$nameB" '
            { lines[NR] = $0 }
            END {
                # Find top-level exclusive directories
                for (i = 1; i <= NR; i++) {
                    line = lines[i]
                    if (line ~ /^\*deleting +[^\/]+\/$/) {
                        path = line; sub(/^\*deleting +/, "", path)
                        excl_b[path] = 1
                    }
                    if (line ~ /^cd\+* +[^\/]+\/$/) {
                        path = line; sub(/^[^ ]+ +/, "", path)
                        excl_a[path] = 1
                    }
                }
                # Output with collapsing
                for (i = 1; i <= NR; i++) {
                    line = lines[i]
                    if (line ~ /^\*deleting/) {
                        path = line; sub(/^\*deleting +/, "", path)
                        skip = 0
                        for (d in excl_b) { if (path != d && index(path, d) == 1) skip = 1 }
                        if (!skip) printf "[ONLY %-20s] %s\n", labelB, path
                        continue
                    }
                    if (line ~ /^cd\+/) {
                        path = line; sub(/^[^ ]+ +/, "", path)
                        skip = 0
                        for (d in excl_a) { if (path != d && index(path, d) == 1) skip = 1 }
                        if (!skip) printf "[ONLY %-20s] %s\n", labelA, path
                        continue
                    }
                    if (line ~ /^>f\+\+\+\+\+/) {
                        path = line; sub(/^[^ ]+ +/, "", path)
                        skip = 0
                        for (d in excl_a) { if (index(path, d) == 1) skip = 1 }
                        if (!skip) printf "[ONLY %-20s] %s\n", labelA, path
                        continue
                    }
                    if (line ~ /^>f.s/) {
                        path = line; sub(/^[^ ]+ +/, "", path)
                        printf "[CHANGED%17s] %s\n", "", path
                    }
                }
            }
        '
    else
        # Verbose output (default)
        rsync -rin8 --size-only --delete "$a/" "$b/" | awk \
            -v labelA="$nameA" -v labelB="$nameB" '
            /^\*deleting/   {sub(/^\*deleting +/, ""); printf "[ONLY %-20s] %s\n", labelB, $0; next}
            /^>f\+\+\+\+\+/ {sub(/^[^ ]+ +/, ""); printf "[ONLY %-20s] %s\n", labelA, $0; next}
            /^>f.s/         {sub(/^[^ ]+ +/, ""); printf "[CHANGED%17s] %s\n", "", $0}
        '
    end
end

diff_dirs.md

diff_dirs

Quick directory comparison using rsync. Compares by file size only (fast).

Installation

Bash/Zsh: Add diff_dirs.bash to ~/.bashrc or ~/.zshrc

Fish: Save diff_dirs.fish to ~/.config/fish/functions/

Usage

diff_dirs [-g] <folderA> <folderB>

Options:
  -g, --group  Collapse exclusive directories into single line

Output:
  [ONLY in A]  - file exists only in folderA
  [ONLY in B]  - file exists only in folderB
  [CHANGED]    - file exists in both but differs

Example

$ diff_dirs ~/project-v1 ~/project-v2
[ONLY project-v1        ] old-file.txt
[ONLY project-v1        ] legacy/config.json
[ONLY project-v1        ] legacy/utils.js
[ONLY project-v2        ] new-feature.ts
[CHANGED                ] README.md
[CHANGED                ] src/index.js

$ diff_dirs -g ~/project-v1 ~/project-v2
[ONLY project-v1        ] old-file.txt
[ONLY project-v1        ] legacy/
[ONLY project-v2        ] new-feature.ts
[CHANGED                ] README.md
[CHANGED                ] src/index.js

How it works

Uses rsync -rin8 --size-only --delete in dry-run mode:

• -r recursive
• -i itemized output
• -n dry-run (no changes)
• -8 preserve unicode filenames
• --size-only compare by size, not checksum (fast)
• --delete shows files only in destination

License

MIT