If the process cannot be found, it is better to return an error.

go.mod

@@ -1,3 +1,3 @@
-module github.com/mitchellh/go-ps
+module github.com/jgbooks/go-ps
 
 go 1.13

process.go

@@ -16,6 +16,13 @@ type Process interface {
 	// PPid is the parent process ID for this process.
 	PPid() int
 
+	// Pgrp is the process group ID of the process
+	Pgrp() int
+
+	// Sid is the session ID of the process
+	Sid() int
+	// TtyNr is the TTYID of the process
+	TtyNr() uint64
 	// Executable name running this process. This is not a path to the
 	// executable.
 	Executable() string
@@ -33,7 +40,7 @@ func Processes() ([]Process, error) {
 
 // FindProcess looks up a single process by pid.
 //
-// Process will be nil and error will be nil if a matching process is
+// Process will be nil and error will be os.ErrNotExist if a matching process is
 // not found.
 func FindProcess(pid int) (Process, error) {
 	return findProcess(pid)

process_darwin.go

@@ -12,6 +12,9 @@ import (
 type DarwinProcess struct {
 	pid    int
 	ppid   int
+	pgrp   int
+	sid    int
+	ttyNr uint64
 	binary string
 }
 
@@ -23,10 +26,23 @@ func (p *DarwinProcess) PPid() int {
 	return p.ppid
 }
 
+func (p *DarwinProcess) Pgrp() int {
+	return p.pgrp
+}
+
+func (p *DarwinProcess) Sid() int {
+	return p.sid
+}
+
 func (p *DarwinProcess) Executable() string {
 	return p.binary
 }
 
+
+func (p *DarwinProcess) TtyNr() uint64 {
+	return p.ttyNr
+}
+
 func findProcess(pid int) (Process, error) {
 	ps, err := processes()
 	if err != nil {
@@ -63,9 +79,13 @@ func processes() ([]Process, error) {
 
 	darwinProcs := make([]Process, len(procs))
 	for i, p := range procs {
+		pgid, _ := syscall.Getpgid(int(p.Pid))
+		sid, _ := syscall.Getsid(int(p.Pid))
 		darwinProcs[i] = &DarwinProcess{
 			pid:    int(p.Pid),
 			ppid:   int(p.PPid),
+			pgrp:   pgid,
+			sid:    sid,
 			binary: darwinCstring(p.Comm),
 		}
 	}

process_freebsd.go

@@ -121,10 +121,21 @@ func (p *UnixProcess) PPid() int {
 	return p.ppid
 }
 
+func (p *UnixProcess) Pgrp() int {
+	return p.pgrp
+}
+
+func (p *UnixProcess) Sid() int {
+	return p.sid
+}
+
 func (p *UnixProcess) Executable() string {
 	return p.binary
 }
 
+func (p *UnixProcess) TtyNr() uint64 {
+	return p.ttyNr
+}
 // Refresh reloads all the data associated with this process.
 func (p *UnixProcess) Refresh() error {
 

process_linux.go

@@ -25,11 +25,12 @@ func (p *UnixProcess) Refresh() error {
 	// Move past the image name and start parsing the rest
 	data = data[binStart+binEnd+2:]
 	_, err = fmt.Sscanf(data,
-		"%c %d %d %d",
+		"%c %d %d %d %d",
 		&p.state,
 		&p.ppid,
 		&p.pgrp,
-		&p.sid)
+		&p.sid,
+		&p.ttyNr)
 
 	return err
 }

process_solaris.go

@@ -80,7 +80,7 @@ func (p *UnixProcess) Refresh() error {
 	if err != nil {
 		return err
 	}
-
+	p.ttyNr=uint64(psinfo.Pr_ttydev)
 	p.ppid = int(psinfo.Pr_ppid)
 	p.binary = toString(psinfo.Pr_fname[:], 16)
 	return nil

process_test.go

@@ -1,8 +1,10 @@
 package ps
 
 import (
+	"log"
 	"os"
 	"testing"
+	"time"
 )
 
 func TestFindProcess(t *testing.T) {
@@ -17,6 +19,9 @@ func TestFindProcess(t *testing.T) {
 	if p.Pid() != os.Getpid() {
 		t.Fatalf("bad: %#v", p.Pid())
 	}
+	time.Sleep(20*time.Second)
+	log.Println(p.Sid())
+	log.Println(p.TtyNr())
 }
 
 func TestProcesses(t *testing.T) {

process_unix.go

@@ -17,7 +17,7 @@ type UnixProcess struct {
 	state rune
 	pgrp  int
 	sid   int
-
+	ttyNr uint64
 	binary string
 }
 
@@ -29,6 +29,18 @@ func (p *UnixProcess) PPid() int {
 	return p.ppid
 }
 
+func (p *UnixProcess) Pgrp() int {
+	return p.pgrp
+}
+
+func (p *UnixProcess) Sid() int {
+	return p.sid
+}
+
+func (p *UnixProcess) TtyNr() uint64 {
+	return p.ttyNr
+}
+
 func (p *UnixProcess) Executable() string {
 	return p.binary
 }
@@ -37,10 +49,9 @@ func findProcess(pid int) (Process, error) {
 	dir := fmt.Sprintf("/proc/%d", pid)
 	_, err := os.Stat(dir)
 	if err != nil {
-		if os.IsNotExist(err) {
-			return nil, nil
-		}
-
+	//	if os.IsNotExist(err) {
+	//		return nil, nil
+	//	}
 		return nil, err
 	}
 

process_windows.go

@@ -42,6 +42,8 @@ type PROCESSENTRY32 struct {
 type WindowsProcess struct {
 	pid  int
 	ppid int
+	pgrp int
+	sid  int
 	exe  string
 }
 
@@ -53,10 +55,21 @@ func (p *WindowsProcess) PPid() int {
 	return p.ppid
 }
 
+func (p *WindowsProcess) Pgrp() int {
+	return p.pgrp
+}
+
+func (p *WindowsProcess) Sid() {
+	return p.sid
+}
+
 func (p *WindowsProcess) Executable() string {
 	return p.exe
 }
 
+func (p *WindowsProcess) TtyNr() uint64 {
+	return p.ttyNr
+}
 func newWindowsProcess(e *PROCESSENTRY32) *WindowsProcess {
 	// Find when the string ends for decoding
 	end := 0