112 lines
2.7 KiB
Markdown
112 lines
2.7 KiB
Markdown
---
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name: content-hash
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description: OS-aware content hashing for files and workspace fingerprints using built-in system tools only.
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---
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# Content Hash
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Use this skill when an agent needs deterministic hashes for files or a workspace fingerprint without external dependencies.
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## Protocol
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Use only tools that are present by default on the target OS.
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Do not require Python, Node.js, or external packages.
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Prefer `md5`-compatible output across all platforms.
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## Detect OS
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Select the command family by OS:
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1. Linux: `md5sum`
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2. macOS: `md5`
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3. Windows: PowerShell `Get-FileHash -Algorithm MD5`
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If the agent already knows the OS from runtime context, use it directly.
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## File Hash
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### Linux
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```sh
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md5sum "docs/ARCHITECTURE.md" | awk '{print $1}'
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```
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### macOS
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```sh
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md5 -q "docs/ARCHITECTURE.md"
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```
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### Windows PowerShell
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```powershell
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(Get-FileHash -Algorithm MD5 'docs/ARCHITECTURE.md').Hash.ToLower()
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```
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## Workspace Fingerprint
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To compute a workspace fingerprint, hash a deterministic manifest of relevant files.
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Sort paths before hashing.
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Include both relative path and file content digest in the manifest.
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### Linux
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```sh
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{
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for path in $(printf '%s\n' docs/ARCHITECTURE.md docs/CODE_STYLE.md docs/FINDINGS.md | sort); do
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if [ -f "$path" ]; then
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printf '%s:' "$path"
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md5sum "$path" | awk '{print $1}'
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fi
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done
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} | md5sum | awk '{print $1}'
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```
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### macOS
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```sh
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{
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for path in $(printf '%s\n' docs/ARCHITECTURE.md docs/CODE_STYLE.md docs/FINDINGS.md | sort); do
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if [ -f "$path" ]; then
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printf '%s:' "$path"
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md5 -q "$path"
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printf '\n'
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fi
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done
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} | md5 -q
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```
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### Windows PowerShell
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```powershell
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$paths = @('docs/ARCHITECTURE.md', 'docs/CODE_STYLE.md', 'docs/FINDINGS.md') | Sort-Object
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$manifest = foreach ($path in $paths) {
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if (Test-Path $path) {
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$hash = (Get-FileHash -Algorithm MD5 $path).Hash.ToLower()
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"${path}:$hash"
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}
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}
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$bytes = [System.Text.Encoding]::UTF8.GetBytes(($manifest -join "`n"))
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$stream = [System.IO.MemoryStream]::new(,$bytes)
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try {
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(Get-FileHash -Algorithm MD5 -InputStream $stream).Hash.ToLower()
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} finally {
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$stream.Dispose()
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}
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```
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## Output Normalization
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Normalize all emitted hashes to lowercase hexadecimal.
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Do not include filenames, labels, or surrounding prose in the stored hash fields.
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## Error Handling
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If the OS-native hashing command is unavailable on the current platform:
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1. report that hash evidence could not be computed
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2. set the relevant trust state to `unknown`
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3. write a concrete reason naming the missing hashing command
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If a file is missing, do not fabricate a hash.
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Only hash files that actually exist. |