What causes "process %d not found: %w" in pranshuparmar/witr?

Verify the PID exists (`ps -p `) before retrying; if not, the process is gone.

process %d not found: %w

Error message

process %d not found: %w

What it means

FreeBSD ReadProcess runs `ps -p <pid> -o ...`; a non-zero ps exit (normally because the PID does not exist) yields this error with the exec error wrapped via %w. It is the primary 'process is gone' signal on FreeBSD.

Source

Thrown at internal/proc/process_freebsd.go:35

func ReadProcess(pid int) (model.Process, error) {
	// Reject PID 0 (and negatives): on FreeBSD `ps -p 0` returns the kernel
	// swapper, which is not a real userland target. Matches the other platforms.
	if pid <= 0 {
		return model.Process{}, fmt.Errorf("invalid pid %d", pid)
	}
	pidStr := strconv.Itoa(pid)

	// Format: pid(0) ppid(1) uid(2) jid(3) state(4) pcpu(5) rss(6) lstart(7-11) args(12+)
	// comm is excluded because it can contain spaces, which breaks strings.Fields parsing.
	// The display name is derived from args instead.
	cmd := exec.Command("ps", "-p", pidStr,
		"-o", "pid=", "-o", "ppid=", "-o", "uid=", "-o", "jid=",
		"-o", "state=", "-o", "pcpu=", "-o", "rss=",
		"-o", "lstart=", "-o", "args=")
	cmd.Env = buildEnvForPS()
	out, err := cmd.Output()
	if err != nil {
		return model.Process{}, fmt.Errorf("process %d not found: %w", pid, err)
	}

	line := strings.TrimSpace(string(out))
	if line == "" {
		return model.Process{}, fmt.Errorf("process %d not found", pid)
	}

	fields := strings.Fields(line)
	if len(fields) < 12 {
		return model.Process{}, fmt.Errorf("unexpected ps output format for pid %d: got %d fields in %q", pid, len(fields), line)
	}

	ppid, _ := strconv.Atoi(fields[1])
	uid, _ := strconv.Atoi(fields[2])
	jid := fields[3]
	state := fields[4]
	cpuPct, _ := strconv.ParseFloat(fields[5], 64)
	rssKB, _ := strconv.ParseFloat(fields[6], 64)

View on GitHub (pinned to dc4fa1da82)

Solutions

Verify the PID exists (`ps -p <pid>`) before retrying; if not, the process is gone.
Retry promptly to minimize the exit race.
Inspect the wrapped error to distinguish 'No such process' from 'executable not found' (install/procps availability issue).
Inspect the parent process instead if the child exited; check for PID reuse with fresh data.

Defensive patterns

Strategy: try-catch

Validate before calling

// FreeBSD: existence check before ReadProcess
if out, err := exec.Command("ps", "-p", strconv.Itoa(pid), "-o", "pid=").Output(); err != nil || len(strings.TrimSpace(string(out))) == 0 {
    return fmt.Errorf("pid %d not running", pid)
}

Try / catch

proc, err := proc.ReadProcess(pid)
if err != nil {
    if strings.Contains(err.Error(), "not found") {
        // target exited: unwrap %w to confirm 'No such process'
    }
}

Prevention

Read the process promptly after PID discovery
Confirm ps exists in jails/containers where the tool runs
Unwrap the error to separate process-exit from environment failures

When it happens

Trigger: ReadProcess on a PID that already terminated (ps exit 1), or exec failures such as ps missing from PATH, both surfaced wrapped in this message.

Common situations: Target exited between discovery and lookup; minimal jails/containers lacking ps; supervisor restarted the process with a new PID.

Related errors

AI-assisted analysis of pranshuparmar/witr@dc4fa1da82 (2026-09-01). Data as JSON: /api/errors/88fd661d262d87e7. Report an issue: GitHub.