数据驱动 shell 编程？请提出建议

Question

我想将我的 shell 脚本转换为使用数据驱动方法。但是由于在任何 shell 中都没有 "tables" 类型值（据我所知），有什么建议的替代方法可以做到这一点？

我正在寻找的解决方案可以让人们做如下事情：

animals = [['horse', 300 'brown'],
           ['cat', 3, 'black'],
           ['elephant', 3000, 'grey'],
           ['mouse', 0.3, 'grey']]
for a in animals ; do
  echo "A typical $a[1] is $a[3] and weighs about $a[2] kilograms."
done

更准确地说，我想尝试一些命令，看看其中一个是否可用，然后向它发送参数：

commands = [['c1', '-m', '-i'],
            ['c2', '-message', '-icon'],
            ['c3', '/m', '/i']]
for c in commands ; do
  if exists c[1] ; then
    command = c[1]
    message_option = c[2]
    icon_option = c[3]
    break;
  fi
done
$command $message_option "message" $icon_option icon

Answer 1

试试这个？

cat file
'horse', 300, 'brown'
'cat', 3, 'black'
'elephant', 3000, 'grey'
'mouse', 0.3, 'grey'

for i in {1..4} ; 
do 
    animal=$(awk -F, -v var="$i" 'NR== var {print }' file) 
    weight=$(awk -F, -v var="$i" 'NR== var {print }' file) 
    colour=$(awk -F, -v var="$i" 'NR== var {print }' file) 
    echo "A typical "$animal" is "$colour" and weighs about "$weight" kilos." 
done

输出-

A typical 'horse' is 'brown' and weighs about  300 kilos.
A typical 'cat' is  'black' and weighs about  3 kilos.
A typical 'elephant' is  'grey' and weighs about  3000 kilos.
A typical 'mouse' is  'grey' and weighs about  0.3 kilos.

Answer 2

您可以根据需要在 bash 中定义和使用 associative-arrays。

#!/bin/bash

# declaring the Associative array
declare -a animals

animals[0]="'horse':300:'brown'"
animals[1]="'cat':3:'black'"
animals[2]="'elephant':3000:'grey'"
animals[3]="'mouse':0.3:'grey'"

for animal in "${animals[@]}"
do
    myArray=(${animal//:/ })
    printf "A typical "${myArray[0]}" is "${myArray[2]}" and weighs about "${myArray[1]}" kilograms.\n"
done

上面唯一棘手的部分是 parameter-expansion 类型

${parameter/pattern/string}
          The pattern is expanded to produce a pattern just as in filename expansion. Parameter is expanded and the longest match of pattern against its value is replaced with string. 
If pattern begins with ‘/’, all matches of pattern are replaced with string. Normally only the first match is replaced.

因此，理想情况下，字符串 'horse':300:'brown' 被拆分为单独的元素并存储在数组 myArray 中，该数组稍后用于访问 C 样式循环中的单独元素。

Answer 3

不需要任何 bashisms。这可以通过 while read 循环读取的 here-document 巧妙地解决：

#!/bin/sh
while read animal weigth colour; do
  printf '%s\n' "A typical $animal is $colour and weighs about $weight kilos."
done << EOF
horse 300 brown
cat 3 black
elephant 3000 grey
mouse 0.3 grey
EOF

观察这是如何按名称引用元素的，而不是使用 1、2、3 的神秘索引。它没有 fork/exec 任何外部命令，并且击败了另一个答案中看到的循环体中的 3 个 awk放下手。

数据驱动 shell 编程？请提出建议

Datadriven shell programming? Suggestions, please

shell

data-driven