shell的多进程并发和控制

1. 单个进程的example
   

    1 #!/bin/bash
    2 start_time=`date "+%s"`
    3 echo "start_time is $start_time"
    4 for((i=1;i<=4;i++))
    5 do
    6    echo success $i;sleep 2
    7 done 
    8 wait
    9 end_time=`date "+%s"`
   10 echo "end_time is $end_time"
   11 echo "TIME: `expr $end_time - $start_time`"

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   上面的wait是多余的；执行的结果如下：

   

   1 start_time is 1584504244
   2 success 1
   3 success 2
   4 success 3
   5 success 4
   6 end_time is 1584504252
   7 TIME: 8

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   由于是顺序执行，每次只执行一个，所以使用8s完成
2. 未控制的多进程执行example
   

    1 #!/bin/bash
    2 start_time=`date "+%s"`
    3 echo "start_time is $start_time"
    4 for((i=1;i<=4;i++))
    5 do
    6     {    
    7    echo success $i;sleep 2
    8    }&
    9 done 
   10 wait
   11 end_time=`date "+%s"`
   12 echo "end_time is $end_time"
   13 echo "TIME: `expr $end_time - $start_time`"

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   执行的结果如下：

   

   1 start_time is 1584504404
   2 success 1
   3 success 2
   4 success 3
   5 success 4
   6 end_time is 1584504406
   7 TIME: 2

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   由于是并行执行，所以使用2s完成；加入各个进程执行时间

3. 控制执行的多进程example
   

    1 #!/bin/bash
    2 
    3 trap "exec 1000>&-;exec 1000<&-;exit 0" 2
    4 
    5 mkfifo testfifo
    6 exec 1000<>testfifo
    7 rm -rf testfifo
    8 
    9 for((n=1;n<=10;n++))
   10 do
   11     echo >&1000
   12 done
   13 
   14 start=`date "+%s"`
   15 
   16 for((i=1;i<100;i++))
   17 do
   18     read -u1000
   19     {
   20         echo success $i; sleep 2
   21         echo >&1000    
   22     }&
   23 done
   24 
   25 wait
   26 end=`date "+%s"`
   27 
   28 echo "TIME: `expr $end - $start`"
   29 
   30 exec 1000>&-
   31 exec 1000<&-

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   执行结果如下：

   

     1 success 1
     2 success 2
     3 success 3
     4 success 4
     5 success 5
     6 success 6
     7 success 7
     8 success 8
     9 success 9
    10 success 10
    11 success 11
    12 success 12
    13 success 13
    14 success 14
    15 success 15
    16 success 16
    17 success 17
    18 success 18
    19 success 19
    20 success 20
    21 success 21
    22 success 22
    23 success 23
    24 success 24
    25 success 25
    26 success 26
    27 success 27
    28 success 28
    29 success 29
    30 success 30
    31 success 31
    32 success 32
    33 success 33
    34 success 34
    35 success 35
    36 success 36
    37 success 37
    38 success 38
    39 success 39
    40 success 40
    41 success 41
    42 success 42
    43 success 43
    44 success 44
    45 success 45
    46 success 46
    47 success 47
    48 success 48
    49 success 49
    50 success 50
    51 success 51
    52 success 52
    53 success 53
    54 success 54
    55 success 55
    56 success 56
    57 success 57
    58 success 58
    59 success 59
    60 success 60
    61 success 61
    62 success 62
    63 success 63
    64 success 64
    65 success 65
    66 success 66
    67 success 67
    68 success 68
    69 success 69
    70 success 70
    71 success 71
    72 success 72
    73 success 73
    74 success 74
    75 success 75
    76 success 76
    77 success 77
    78 success 78
    79 success 79
    80 success 80
    81 success 81
    82 success 82
    83 success 83
    84 success 84
    85 success 85
    86 success 86
    87 success 87
    88 success 88
    89 success 89
    90 success 90
    91 success 91
    92 success 92
    93 success 93
    94 success 94
    95 success 95
    96 success 96
    97 success 97
    98 success 98
    99 success 99
   100 TIME: 20

   View Code

   上述的example每次执行10个线程，每次需要2秒执行完成，总共执行100个线程，总计20秒。