Path lexical common ancestor

path-lexical-common-ancestor · version 1.0.0 · File paths (lexical) · free, no key needed

Compute the deepest common ancestor directory of a set of paths.

Use when you need to: common ancestor · longest common path prefix · shared ancestor directory.

Supported

• common ancestor
• longest common path prefix
• shared ancestor directory

Not supported

• stat file
• resolve symlinks
• filesystem access

Behavior

• Compute deepest common ancestor directory by comparing normalized segments.
• ancestor is common prefix directory path, or null if no common prefix.
• depth is number of common directory segments (0 if no common prefix).
• Windows: case-insensitive segment comparison. POSIX: case-sensitive.
• Paths on different drives return {ancestor:null,format:"windows",depth:0}.
• Single path input: ancestor is the parent directory of that path.

Input

• paths (array of string, required): min items 1; max items 500; each min length 1; each max length 4096
• format (one of "posix", "windows", "auto", optional)

Output

• ancestor (string or null, required)
• format (one of "posix", "windows", required)
• depth (integer, required): min 0

Limits

• max paths: 500
• max path bytes: 4096

Example

Request input:

{
  "paths": [
    "/a/b/c",
    "/a/b/d",
    "/a/b/e/f"
  ]
}

Response:

{
  "result": {
    "ancestor": "/a/b",
    "format": "posix",
    "depth": 2
  }
}

How to call it

MCP

Connect https://computefirst.net/mcp (setup), then call execute with:

{
  "id": "path-lexical-common-ancestor",
  "version": "1.0.0",
  "input": {
    "paths": [
      "/a/b/c",
      "/a/b/d",
      "/a/b/e/f"
    ]
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/path-lexical-common-ancestor/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"paths":["/a/b/c","/a/b/d","/a/b/e/f"]}'

The machine-readable contract is at /v1/tools/path-lexical-common-ancestor/versions/1.0.0.

CLI

node cli.mjs run path-lexical-common-ancestor 1.0.0 --input input.json --base-url https://computefirst.net

Get the client at /clients/cli/.

Related tools

• Path lexical contains: Check whether a child path is lexically inside a parent directory.
• Path set prefix strip: Strip a common directory prefix or base path from an array of paths lexically.
• Path lexical join: Join an array of path segments lexically, resolving absolute reset boundaries and normalizing separators.
• Path lexical normalize: Normalize a path lexically: collapse redundant separators, resolve "." and ".." segments.
• Path lexical parse: Decompose a file path into its lexical components without accessing the filesystem.
• Path lexical relative: Compute the lexical relative path from one path to another without filesystem access.