github.com/u-root/u-root@v7.0.1-0.20200915234505-ad7babab0a8e+incompatible/cmds/exp/getty/getty.go (about)

     1  // Copyright 2019 the u-root Authors. All rights reserved
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // getty Open a TTY and invoke a shell
     6  // There are no special options and no login support
     7  // Also getty exits after starting the shell so if one exits the shell, there
     8  // is no more shell!
     9  //
    10  // Synopsis:
    11  //     getty <port> <baud> [term]
    12  package main
    13  
    14  import (
    15  	"flag"
    16  	"fmt"
    17  	"log"
    18  	"os"
    19  	"os/exec"
    20  	"strconv"
    21  
    22  	"github.com/u-root/u-root/pkg/termios"
    23  	"github.com/u-root/u-root/pkg/upath"
    24  )
    25  
    26  var (
    27  	verbose = flag.Bool("v", false, "verbose log")
    28  	debug   = func(string, ...interface{}) {}
    29  	cmdList []string
    30  	envs    []string
    31  )
    32  
    33  func init() {
    34  	r := upath.UrootPath
    35  	cmdList = []string{
    36  		r("/bin/defaultsh"),
    37  		r("/bin/sh"),
    38  	}
    39  }
    40  
    41  func main() {
    42  	flag.Parse()
    43  
    44  	if *verbose {
    45  		debug = log.Printf
    46  	}
    47  
    48  	port := flag.Arg(0)
    49  	baud, err := strconv.Atoi(flag.Arg(1))
    50  	if err != nil {
    51  		baud = 0
    52  	}
    53  	term := flag.Arg(2)
    54  
    55  	log.SetPrefix("getty: ")
    56  
    57  	ttyS, err := termios.NewTTYS(port)
    58  	if err != nil {
    59  		log.Fatalf("Unable to open port %s: %v", port, err)
    60  	}
    61  
    62  	if _, err := ttyS.Serial(baud); err != nil {
    63  		log.Printf("Unable to configure port %s and set baudrate %d: %v", port, baud, err)
    64  	}
    65  
    66  	// Output the u-root banner
    67  	log.New(ttyS, "", log.LstdFlags).Printf("Welcome to u-root!")
    68  	fmt.Fprintln(ttyS, `                              _`)
    69  	fmt.Fprintln(ttyS, `   _   _      _ __ ___   ___ | |_`)
    70  	fmt.Fprintln(ttyS, `  | | | |____| '__/ _ \ / _ \| __|`)
    71  	fmt.Fprintln(ttyS, `  | |_| |____| | | (_) | (_) | |_`)
    72  	fmt.Fprintln(ttyS, `   \__,_|    |_|  \___/ \___/ \__|`)
    73  	fmt.Fprintln(ttyS)
    74  
    75  	if term != "" {
    76  		err = os.Setenv("TERM", term)
    77  		if err != nil {
    78  			debug("Unable to set 'TERM=%s': %v", port, err)
    79  		}
    80  	}
    81  	envs = os.Environ()
    82  	debug("envs %v", envs)
    83  
    84  	for _, v := range cmdList {
    85  		debug("Trying to run %v", v)
    86  		if _, err := os.Stat(v); os.IsNotExist(err) {
    87  			debug("%v", err)
    88  			continue
    89  		}
    90  
    91  		cmd := exec.Command(v)
    92  		cmd.Env = envs
    93  		ttyS.Ctty(cmd)
    94  		debug("running %v", cmd)
    95  		if err := cmd.Start(); err != nil {
    96  			log.Printf("Error starting %v: %v", v, err)
    97  			continue
    98  		}
    99  		if err := cmd.Process.Release(); err != nil {
   100  			log.Printf("Error releasing process %v:%v", v, err)
   101  		}
   102  		// stop after first valid command
   103  		return
   104  	}
   105  	log.Printf("No suitable executable found in %+v", cmdList)
   106  }