How to Check Which MongoDB Version Is Currently Active Using m

The m version manager determines the active MongoDB installation by executing mongod --version from the symlinked $M_BIN_DIR directory and parsing the output to extract the version string, including Enterprise edition detection.

The m tool by aheckmann/m is a lightweight MongoDB version manager that simplifies switching between server releases. When you activate a specific MongoDB version, m creates symbolic links in a dedicated binary directory, enabling quick identification of which build is currently in use. Understanding how to check which MongoDB version is currently active using m ensures you're running the expected server in your development or production environments.

How m Detects the Active MongoDB Version

At the core of version detection is the symlinked binary directory referenced by the $M_BIN_DIR environment variable. When you activate a version, m populates this directory with symbolic links pointing to the selected release's bin folder (excluding a few tool binaries).

The check_current_version function defined in bin/m (lines 40-48) performs the actual runtime detection:

check_current_version() {
    which $M_BIN_DIR/mongod &> /dev/null
    if test $? -eq 0; then
        active=`$M_BIN_DIR/mongod --version | grep "version\s*v[0-9]" \
              | grep -E -o '[0-9]+\.[0-9]+\.[0-9]+([-_\.][a-zA-Z0-9]+)?' | head -1
        ent=`$M_BIN_DIR/mongod --version | grep -E '(modules\"?:|\"?enterprise\"?)' \
              | grep -v -E 'modules"?:[[:space:]]*\[.*' | grep -v -E 'modules"?:[[:space:]]*none'`
        if [[ $ent == *1 ]]; then active="$active-ent"; fi
    fi
}

This function runs $M_BIN_DIR/mongod --version and uses grep patterns to extract the semantic version number. It also detects Enterprise builds by checking the output for enterprise modules or specific module declarations, appending -ent to the version string when applicable.

Commands to Check the Active MongoDB Version

List Installed Versions with the Active Indicator

Running m without arguments invokes display_versions, which internally calls check_current_version before printing. According to the aheckmann/m source code, the active version appears with a ✔︎ marker:

$ m
  5.0.15
  6.0.5
✔ 7.0.12

Display the Binary Path of the Active Version

The m bin command utilizes display_bin_path_for_version to print the absolute path to the currently active version's bin directory. This resolves the symlinks in $M_BIN_DIR to their actual installation location:

$ m bin
/home/youruser/.local/m/versions/7.0.12/bin

Query Specific Version Paths

To verify the installation path of a specific release without activating it, use m bin <version> or m which <version>. This returns the path to the latest installed version matching the provided identifier:

$ m bin 6.0.5
/home/youruser/.local/m/versions/6.0.5/bin

Practical Usage Examples

Here are common workflows for verifying your MongoDB environment using the m CLI:

# Check which version is active (marked with ✔︎)

$ m

# Get the absolute path to the active version's binaries

$ m bin

# Verify the path for a specific installed version

$ m which 5.0.15

# Start the currently active mongod directly

$ m use

Summary

• Symbolic link inspection: m identifies the active version by examining symlinks in the $M_BIN_DIR directory that point to the selected release.
• Version parsing: The check_current_version function in bin/m executes mongod --version and extracts the version using regex pattern matching.
• Enterprise detection: The tool automatically appends -ent to the version string when it detects Enterprise modules in the binary output.
• User commands: Use m to list versions with indicators, m bin to show the active path, and m bin <version> to query specific installations.

Frequently Asked Questions

How does m determine which MongoDB version is active?

The tool checks the $M_BIN_DIR environment variable for existing symlinked binaries and executes mongod --version from that location. The check_current_version function parses the command output to extract the semantic version number and detect if it's an Enterprise build.

What is $M_BIN_DIR in the m version manager?

$M_BIN_DIR is the directory where m creates symbolic links to the currently activated MongoDB version's binaries. This directory typically resides at ~/.local/m/bin and contains symlinks to mongod, mongo, and other server tools that resolve to the active version's installation path.

Can m detect if I'm running MongoDB Enterprise Edition?

Yes. The check_current_version function specifically searches the mongod --version output for enterprise modules or the "enterprise" string. When detected, it appends -ent to the version identifier shown in the listing output.

How do I switch to a different MongoDB version using m?

Run m use <version> to activate a specific release. This command updates the symlinks in $M_BIN_DIR to point to the requested version's installation directory, immediately making it the new active version for all subsequent MongoDB operations.

{
  "mcpServers": {
    "instagit": {
      "command": "npx",
      "args": ["-y", "instagit@latest"]
    }
  }
}