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rit cat-file

Display the contents or information about a repository object.

Synopsis​

rit cat-file -p <object-hash>

Description​

This plumbing command reads an object from the database, decompresses it, and displays its contents.

Options​

OptionDescription
-pPretty-print the object contents based on its type

How It Works​

  1. Take the object hash (e.g., abc123...)
  2. Find the file at .rit/objects/ab/c123...
  3. Decompress with zlib
  4. Parse the header to get type and size
  5. Display the content

Object Format​

Objects are stored as:

<type> <size>\0<content>

After decompression, we parse:

  • Type: "blob", "tree", or "commit"
  • Size: Content length in bytes
  • Content: The actual data after the null byte

Examples​

Reading a Blob​

# Store a file
$ echo "Hello, World!" > hello.txt
$ rit hash-object -w hello.txt
8ab686eafeb1f44702738c8b0f24f2567c36da6d

# Read it back
$ rit cat-file -p 8ab686eafeb1f44702738c8b0f24f2567c36da6d
Hello, World!

Reading a Tree​

$ rit cat-file -p <tree-hash>
100644 blob abc123...    README.md
100755 blob def456...    build.sh
040000 tree 789abc...    src

Reading a Commit​

$ rit cat-file -p <commit-hash>
tree 4b825dc642cb6eb9a060e54bf8d69288fbee4904
parent a1b2c3d4e5f6789...
author John Doe <john@example.com> 1234567890 +0000
committer John Doe <john@example.com> 1234567890 +0000

Initial commit

Implementation Details​

pub fn read_object(repo: &Repository, hash: &str) -> Result<GitObject> {
    let object_path = repo.objects_dir()
        .join(&hash[..2])
        .join(&hash[2..]);

    // Read and decompress
    let compressed = fs::read(&object_path)?;
    let mut decoder = ZlibDecoder::new(&compressed[..]);
    let mut data = Vec::new();
    decoder.read_to_end(&mut data)?;

    // Parse header (everything before null byte)
    let null_pos = data.iter().position(|&b| b == 0).unwrap();
    let header = String::from_utf8_lossy(&data[..null_pos]);
    let (object_type, size) = parse_header(&header)?;

    // Content is everything after null byte
    let content = data[null_pos + 1..].to_vec();

    Ok(GitObject { object_type, size, content })
}

Error Cases​

# Object doesn't exist
$ rit cat-file -p nonexistent123
fatal: object not found: nonexistent123

# Hash too short
$ rit cat-file -p abc
fatal: hash too short: abc

See Also​