Add basic ps

cmd/cat/cat.go

@@ -21,6 +21,7 @@ func cat(in io.Reader, out io.Writer, name string) error {
 
 	for {
 		n, err := in.Read(buf[:])
+
 		if n <= 0 {
 			break
 		}

cmd/ps/ps.go

@@ -0,0 +1,211 @@
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"os"
+	"strings"
+)
+
+type (
+	status []string
+)
+
+const procDir = "/proc"
+
+const (
+	STpid      uint8 = 0
+	STcomm           = 1
+	STstat           = 2
+	STppid           = 3
+	STpgrp           = 4
+	STsid            = 5
+	STnice           = 18
+	STnthreads       = 19
+	STvmsize         = 22
+	STrss            = 23
+	STproc           = 38
+	STLAST           = 52
+)
+
+var (
+	states map[rune]string
+)
+
+func init() {
+	states = map[rune]string{
+		'R': "running",
+		'S': "sleeping",
+		'D': "sleep/disk",
+		'Z': "zombie",
+		'T': "stopped",
+		't': "tracing stop",
+		'X': "dead",
+		'x': "dead",
+		'K': "wakekill",
+		'W': "waking",
+		'P': "Parked",
+	}
+}
+
+func newStatus(statstr string) (status, error) {
+	stat := strings.Split(statstr, " ")
+
+	if len(stat) != STLAST {
+		return nil, fmt.Errorf("malformed stat line: (length %d) %s",
+			len(stat), statstr)
+	}
+
+	return status(stat), nil
+}
+
+func (s status) pid() string      { return s[STpid] }
+func (s status) comm() string     { return s[STcomm] }
+func (s status) state() string    { return s[STstat] }
+func (s status) ppid() string     { return s[STppid] }
+func (s status) nice() string     { return s[STnice] }
+func (s status) nthreads() string { return s[STnthreads] }
+func (s status) vmsize() string   { return s[STvmsize] }
+func (s status) rss() string      { return s[STrss] }
+func (s status) lastproc() string { return s[STproc] }
+
+func (s status) String() string {
+	return strings.Join(s, " ")
+}
+
+func getpids() ([]os.FileInfo, error) {
+	var pids []os.FileInfo
+
+	files, err := ioutil.ReadDir(procDir)
+
+	if err != nil {
+		return nil, err
+	}
+
+	for _, f := range files {
+		fname := f.Name()
+
+		if !f.IsDir() {
+			continue
+		}
+
+		if len(fname) > 0 && (fname[0] < '0' || fname[0] > '9') {
+			continue
+		}
+
+		pids = append(pids, f)
+	}
+
+	return pids, nil
+}
+
+func readall(r io.Reader) ([]byte, error) {
+	data := make([]byte, 0, 8192)
+	buf := make([]byte, 8192)
+
+	for {
+		n, err := r.Read(buf)
+
+		if err != nil && err != io.EOF {
+			return nil, err
+		}
+
+		if n <= 0 {
+			break
+		}
+
+		data = append(data, buf[:n]...)
+	}
+
+	return data, nil
+}
+
+func cmdline(pid os.FileInfo) (string, error) {
+	file, err := os.Open(procDir + "/" + pid.Name() + "/cmdline")
+
+	if err != nil {
+		return "", err
+	}
+
+	defer file.Close()
+
+	cmdbytes, err := readall(file)
+
+	if err != nil {
+		return "", err
+	}
+
+	cmdline := string(bytes.Replace(cmdbytes, []byte{0}, []byte{' '}, -1))
+	return cmdline, nil
+}
+
+func getstat(pid os.FileInfo) (status, error) {
+	file, err := os.Open(procDir + "/" + pid.Name() + "/stat")
+
+	if err != nil {
+		return nil, err
+	}
+
+	defer file.Close()
+
+	statbytes, err := readall(file)
+
+	if err != nil {
+		return nil, err
+	}
+
+	stat, err := newStatus(string(statbytes))
+
+	if err != nil {
+		return nil, err
+	}
+
+	return stat, nil
+}
+
+func showpid(pid os.FileInfo) error {
+	user, err := pidowner(pid)
+
+	if err != nil {
+		return err
+	}
+
+	cmdline, err := cmdline(pid)
+
+	if err != nil {
+		return err
+	}
+
+	status, err := getstat(pid)
+
+	if err != nil {
+		return err
+	}
+
+	fmt.Printf("%s\t%s\t%s\t%.20s\n", user, status.pid(), status.ppid(), cmdline)
+	return nil
+}
+
+func ps() error {
+	pids, err := getpids()
+
+	if err != nil {
+		return err
+	}
+
+	for _, pid := range pids {
+		if err = showpid(pid); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func main() {
+	if err := ps(); err != nil {
+		fmt.Fprintf(os.Stderr, "%s\n", err)
+	}
+}

cmd/ps/ps_linux.go

@@ -0,0 +1,30 @@
+// +build linux
+package main
+
+import (
+	"fmt"
+	"os"
+	"os/user"
+	"strconv"
+	"syscall"
+)
+
+func pidowner(pid os.FileInfo) (string, error) {
+	var (
+		stat *syscall.Stat_t
+		ok   bool
+	)
+
+	if stat, ok = pid.Sys().(*syscall.Stat_t); !ok {
+		return "", fmt.Errorf("Failed to get file owner")
+	}
+
+	user, err := user.LookupId(strconv.Itoa(int(stat.Uid)))
+
+	if err != nil {
+		return "", err
+	}
+
+	return user.Username, nil
+
+}