System status Kdialog greeter

welcome.go

package main

import (
        "bytes"
        "fmt"
        "log"
        "os/exec"
        "strings"
        "syscall"
        "time"
)

func main() {
        //This would typically go in .xprofile
        //Build up a status message and present it with kdialog
        welcome := bytes.NewBuffer(nil)

        // Boot info
        uname := syscall.Utsname{}
        err := syscall.Uname(&uname)
        if err != nil {
                log.Fatal(err)
        }
        fmt.Fprintf(welcome, "Welcome to %s: %s %s (%s)\n",
                str(uname.Nodename[:]),
                str(uname.Sysname[:]),
                str(uname.Release[:]),
                str(uname.Machine[:]))

        fmt.Fprintln(welcome, "\nLast boot:\n----------")
        last := try("last", "reboot", "--limit", "1")
        date := strings.Fields(string(last))[4:8]
        fmt.Fprintf(welcome, "%s\n\n", strings.Join(date, " "))

        analyze := try("systemd-analyze")
        analyze = bytes.Replace(analyze, []byte("graphical"), []byte("Graphichal"), 1)
        fmt.Fprintf(welcome, "%s\n", analyze)

        // Boot errors
        fmt.Fprintln(welcome, "Boot errors:\n-------")
        critical := try("journalctl", "-r", "-b", "--no-pager", "-p", "err", "-q")
        if len(critical) == 0 {
                fmt.Fprintln(welcome, "no errors detected")
        } else {
                fmt.Fprintf(welcome, "%s\n", critical)
        }

        // Failed systemd units
        fmt.Fprintln(welcome, "Failed units:\n-------------")
        failed := try("systemctl", "--failed")
        fmt.Fprintf(welcome, "%s\n", failed)

        // Last logins
        fmt.Fprintln(welcome, "Last logins:\n------------")
        last = try("last")
        var i int
        for _, entry := range strings.Split(string(last), "\n") {
                if i == 5 {
                        break
                }
                if strings.Contains(entry, "reboot") {
                        continue
                }
                fields := strings.Fields(entry)
                entry = fields[0] + "\t" + strings.Join(fields[2:7], " ")
                fmt.Fprintln(welcome, entry)
                i++
        }

        fmt.Fprintln(welcome, "\nNice to see you!")

        kdialog := exec.Command("kdialog", "--textbox", "-", "1150", "800")
        kdialog.Stdin = welcome
        kdialog.Run()
}

func str(arr []int8) string {
        b := make([]byte, 0, len(arr))
        for _, v := range arr {
                if v == 0x00 {
                        break
                }
                b = append(b, byte(v))
        }
        return string(b)
}

func try(name string, args ...string) (out []byte) {
        var err error
        for {
                out, err = exec.Command(name, args...).Output()
                if err == nil {
                        break
                }
                time.Sleep(time.Second)
        }
        return out
}