FuelLabs/sway · error

Failed to execute tasklist command

Error message

Failed to execute tasklist command

What it means

Windows counterpart of the PID liveness check in forc-util's file locking: is_pid_active runs `tasklist /FI "PID eq <pid>"` and this expect panics when tasklist.exe cannot be spawned. As on Unix, the check only runs when an existing lock file's staleness must be determined.

Source

Thrown at forc-util/src/fs_locking.rs:65

            .arg("-p")
            .arg(pid.to_string())
            .output()
            .expect("Failed to execute ps command");

        let output_str = String::from_utf8_lossy(&output.stdout);
        output_str.contains(&format!("{pid} "))
    }

    #[cfg(target_os = "windows")]
    fn is_pid_active(pid: usize) -> bool {
        // Not using sysinfo here because it has compatibility issues with fuel.nix
        // https://github.com/FuelLabs/fuel.nix/issues/64
        use std::process::Command;
        let output = Command::new("tasklist")
            .arg("/FI")
            .arg(format!("PID eq {}", pid))
            .output()
            .expect("Failed to execute tasklist command");

        let output_str = String::from_utf8_lossy(&output.stdout);
        // Check if the output contains the PID, indicating the process is active
        output_str.contains(&format!("{}", pid))
    }

    /// Removes the lock file if it is not locked or the process that locked it is no longer active
    pub fn release(&self) -> io::Result<()> {
        if self.is_locked() {
            Err(io::Error::other(format!(
                "Cannot remove a dirty lock file, it is locked by another process (PID: {:#?})",
                self.get_locker_pid()
            )))
        } else {
            self.remove_file()?;
            Ok(())
        }
    }

View on GitHub (pinned to 47e5e902fa)

Solutions

1. Run builds on a Windows image that includes tasklist.exe (full/Server Core rather than Nano-style minimal images).
2. Remove the stale lock file under the package's out/ directory so the PID check is skipped.
3. Adjust sandbox/AV policy to allow spawning tasklist.exe from build processes.

Example fix

# before
# Windows Nano Server container + stale .forc-lock -> panic "Failed to execute tasklist command"
# after
# use mcr.microsoft.com/windows/servercore (has tasklist) and delete stale lock:
Remove-Item -Recurse out\*.forc-lock; forc build

# PowerShell guard on Windows before forc build
if (-not (Get-Command tasklist -ErrorAction SilentlyContinue)) {
  Write-Error "tasklist.exe unavailable; use a fuller Windows image or fix the sandbox"; exit 1
}

When it happens

Trigger: A lock file is present and the environment cannot spawn tasklist.exe: stripped-down Windows containers (Nano Server style images without the full toolset), AppContainer/restricted tokens denying execute, antivirus or policy blocking CreateProcess, or corrupted System32 tooling.

Common situations: forc build on Windows Server Core/Nano container images; CI runners with hardened process-creation policies; leftover lock files from a forc process that was force-killed.

Related errors

• Failed to execute ps command
• unable to find the user home directory
• Could not get plugin description.
• Could not get homedir
• Failed to execute ps command

AI-assisted analysis of FuelLabs/sway@47e5e902fa (2026-08-16). Data as JSON: /api/errors/8d1b0e249bde9b75. Report an issue: GitHub.