Add FilterProcesses

process.go

@@ -28,7 +28,12 @@ type Process interface {
 // process table, in which case the process table returned might contain
 // ephemeral entities that happened to be running when this was called.
 func Processes() ([]Process, error) {
-	return processes()
+	return processes(nil)
+}
+
+// FilterProcesses returns processes that satisfy the predicate f.
+func FilterProcesses(f func(Process) bool) ([]Process, error) {
+	return processes(f)
 }
 
 // FindProcess looks up a single process by pid.

process_darwin.go

@@ -28,49 +28,54 @@ func (p *DarwinProcess) Executable() string {
 }
 
 func findProcess(pid int) (Process, error) {
-	ps, err := processes()
+	f := func(p Process) bool {
+		if p.Pid() == pid {
+			return true
+		}
+		return false
+	}
+	ps, err := FilterProcesses(f)
+
 	if err != nil {
 		return nil, err
 	}
 
-	for _, p := range ps {
-		if p.Pid() == pid {
-			return p, nil
-		}
+	if len(ps) == 0 {
+		return nil, nil
 	}
 
-	return nil, nil
+	return ps[0], nil
 }
 
-func processes() ([]Process, error) {
+func processes(f func(Process) bool) ([]Process, error) {
 	buf, err := darwinSyscall()
 	if err != nil {
 		return nil, err
 	}
 
-	procs := make([]*kinfoProc, 0, 50)
+	procs := make([]Process, 0, 50)
+	proc := &kinfoProc{}
 	k := 0
 	for i := _KINFO_STRUCT_SIZE; i < buf.Len(); i += _KINFO_STRUCT_SIZE {
-		proc := &kinfoProc{}
 		err = binary.Read(bytes.NewBuffer(buf.Bytes()[k:i]), binary.LittleEndian, proc)
 		if err != nil {
 			return nil, err
 		}
-
 		k = i
-		procs = append(procs, proc)
-	}
 
-	darwinProcs := make([]Process, len(procs))
-	for i, p := range procs {
-		darwinProcs[i] = &DarwinProcess{
-			pid:    int(p.Pid),
-			ppid:   int(p.PPid),
-			binary: darwinCstring(p.Comm),
+		dp := &DarwinProcess{
+			pid:    int(proc.Pid),
+			ppid:   int(proc.PPid),
+			binary: darwinCstring(proc.Comm),
 		}
+		if f != nil && !f(dp) {
+			continue
+		}
+
+		procs = append(procs, dp)
 	}
 
-	return darwinProcs, nil
+	return procs, nil
 }
 
 func darwinCstring(s [16]byte) string {

process_freebsd.go

@@ -172,7 +172,7 @@ func findProcess(pid int) (Process, error) {
 	return newUnixProcess(pid)
 }
 
-func processes() ([]Process, error) {
+func processes(f func(Process) bool) ([]Process, error) {
 	results := make([]Process, 0, 50)
 
 	mib := []int32{CTL_KERN, KERN_PROC, KERN_PROC_PROC, 0}
@@ -198,6 +198,9 @@ func processes() ([]Process, error) {
 			continue
 		}
 		p.ppid, p.pgrp, p.sid, p.binary = copy_params(&k)
+		if f != nil && !f(p) {
+			continue
+		}
 
 		results = append(results, p)
 	}

process_test.go

@@ -2,6 +2,7 @@ package ps
 
 import (
 	"os"
+	"os/exec"
 	"testing"
 )
 
@@ -43,3 +44,34 @@ func TestProcesses(t *testing.T) {
 		t.Fatal("should have Go")
 	}
 }
+
+func TestFilterProcesses(t *testing.T) {
+	// should have go
+	cmd := exec.Command("go")
+	err := cmd.Start()
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	// Return true only if p is the process started by cmd.Start()
+	f := func(p Process) bool {
+		pid := os.Getpid()
+		if p.PPid() == pid {
+			return true
+		}
+		return false
+	}
+	p, err := FilterProcesses(f)
+	_ = cmd.Wait()
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	if len(p) != 1 {
+		t.Fatal("should have one go processe")
+	}
+
+	if p[0].Executable() != "go" && p[0].Executable() != "go.exe" {
+		t.Fatal("should have one go processe")
+	}
+
+}

process_unix.go

@@ -75,7 +75,7 @@ func findProcess(pid int) (Process, error) {
 	return newUnixProcess(pid)
 }
 
-func processes() ([]Process, error) {
+func processes(f func(Process) bool) ([]Process, error) {
 	d, err := os.Open("/proc")
 	if err != nil {
 		return nil, err
@@ -116,6 +116,10 @@ func processes() ([]Process, error) {
 				continue
 			}
 
+			if f != nil && !f(p) {
+				continue
+			}
+
 			results = append(results, p)
 		}
 	}

process_windows.go

@@ -75,21 +75,26 @@ func newWindowsProcess(e *PROCESSENTRY32) *WindowsProcess {
 }
 
 func findProcess(pid int) (Process, error) {
-	ps, err := processes()
+	f := func(p Process) bool {
+		if p.Pid() == pid {
+			return true
+		}
+		return false
+	}
+	ps, err := FilterProcesses(f)
+
 	if err != nil {
 		return nil, err
 	}
 
-	for _, p := range ps {
-		if p.Pid() == pid {
-			return p, nil
-		}
+	if len(ps) == 0 {
+		return nil, nil
 	}
 
-	return nil, nil
+	return ps[0], nil
 }
 
-func processes() ([]Process, error) {
+func processes(f func(Process) bool) ([]Process, error) {
 	handle, _, _ := procCreateToolhelp32Snapshot.Call(
 		0x00000002,
 		0)
@@ -107,7 +112,10 @@ func processes() ([]Process, error) {
 
 	results := make([]Process, 0, 50)
 	for {
-		results = append(results, newWindowsProcess(&entry))
+		p := newWindowsProcess(&entry)
+		if f == nil || f(p) {
+			results = append(results, p)
+		}
 
 		ret, _, _ := procProcess32Next.Call(handle, uintptr(unsafe.Pointer(&entry)))
 		if ret == 0 {