github.com/rkt/rkt@v1.30.1-0.20200224141603-171c416fac02/stage1_fly/stop/stop.go (about)

     1  // Copyright 2016 The rkt Authors
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  //+build linux
    16  
    17  package main
    18  
    19  import (
    20  	"flag"
    21  	"fmt"
    22  	"io/ioutil"
    23  	"os"
    24  	"syscall"
    25  )
    26  
    27  var (
    28  	force bool
    29  )
    30  
    31  func init() {
    32  	flag.BoolVar(&force, "force", false, "Forced stopping")
    33  }
    34  
    35  func readIntFromFile(path string) (i int, err error) {
    36  	b, err := ioutil.ReadFile(path)
    37  	if err != nil {
    38  		return
    39  	}
    40  	_, err = fmt.Sscanf(string(b), "%d", &i)
    41  	return
    42  }
    43  
    44  func main() {
    45  	flag.Parse()
    46  	var sig syscall.Signal
    47  
    48  	if force {
    49  		sig = syscall.SIGKILL
    50  	} else {
    51  		sig = syscall.SIGTERM
    52  	}
    53  
    54  	pid, err := readIntFromFile("pid")
    55  	if err != nil {
    56  		fmt.Fprintf(os.Stderr, "error reading pid: %v\n", err)
    57  		os.Exit(254)
    58  	}
    59  
    60  	// check for process existence, then kill the process otherwise the group
    61  	err = syscall.Kill(pid, syscall.Signal(0))
    62  	if err == nil {
    63  		err = syscall.Kill(pid, sig)
    64  		if err != nil {
    65  			fmt.Fprintf(os.Stderr, "error stopping process %d: %v\n", pid, err)
    66  			os.Exit(254)
    67  		}
    68  	} else {
    69  		pgid, err := readIntFromFile("pgid")
    70  		if err != nil {
    71  			fmt.Fprintf(os.Stderr, "error reading pgid: %v\n", err)
    72  			os.Exit(254)
    73  		}
    74  		err = syscall.Kill(-pgid, sig)
    75  		if err != nil {
    76  			fmt.Fprintf(os.Stderr, "error stopping process group %d: %v\n", pgid, err)
    77  			os.Exit(254)
    78  		}
    79  	}
    80  }