使用环境变量传递参数给命令 [英] Using an environment variable to pass arguments to a command

问题描述

我试图写一个bash脚本，需要一个环境变量，并将它传递给命令。

I'm trying to write a bash script that takes an environment variable and passes it along to a command.

所以，如果我有这样的事情：

So if I had something like:

export OUT="-a=arg1 -b=\"arg2.0 arg2.1\""

我想在我的bash脚本做这样的事情：

I want in my bash script to do something like:

<command> -a=arg1 '-b=arg2.0 arg2.1'

我有一个办法，似乎要做到这一点，但它涉及到使用eval：

I have one approach that seems to do this, but it involves using eval:

eval <command> ${OUT}

如果我包括设置-x 对的命令，我会看到：

If I include set -x right about the command, I will see:

+ eval <command> a=arg1 'b="arg2.0' 'arg2.1"'
++ <command> -a=arg1 '-b=arg2.0 arg.1'

不过，我周围戳使用eval的危险，因为这将采取从用户的输入参数，它是不够理想。

However, I've poked around the dangers of using eval and since this will be taking the arguments from user input, it's less than ideal.

由于这是bash中，我已经使用数组来存储我的论点，并简单地说也算：＆LT;指挥GT; $ ARRAY [@]做我想做的。我一直在试图使用IFS，但我不知道我应该被拆分的。

Since this is bash, I've also considered using arrays to store my arguments and simply put: <command> "$ARRAY[@]" to do what I want. I've been trying to use IFS, but I'm not sure what I should be splitting on.

推荐答案

如果你不是完全僵化关于 $ OUT ，一种可能是重复的格式在选项= 字符串，以便串联。然后，你会写：

If you're not completely inflexible about the format of $OUT, one possibility would be to repeat the option= string to allow for concatenation. Then you'd write:

export OUT="a=arg1 b=arg2.0 b=arg2.1"

如果是可以接受的，下面的脚本将工作

If that is acceptable, the following script will work

#!/bin/bash

# Parse $OUT into an associative array.
# Instead of using $OUT, it would be cleaner to use "$@".
declare -A args
for arg in $OUT; do
  if [[ "$arg" =~ ^([[:alnum:]]+)=(.*)$ ]]; then
    key=${BASH_REMATCH[1]}
    val=${BASH_REMATCH[2]}
    if [[ -z ${args[$key]} ]]; then
      args[$key]=-$key="$val"
    else
      args[$key]+=" $val"
    fi
  fi
done

# Test, approximately as specified
command() { :; }
set -x
command "${args[@]}"
set +x

我不能说我喜欢它不多，但它是最接近我已经能来。

I can't say I like it much, but it's the closest I've been able to come.

下面是一个运行示例：

$ export OUT="a=foo b=bar  b=glitch s9= s9=* "
./command-runner
+ command -a=foo '-b=bar glitch' '-s9= *'
+ :
+ set +x

---

如果您导入bash的功能（例如，在你的bash的启动文件），你可以更好地利用阵列。这里有一个方法：

---

If you import a bash function (for example, in your bash startup file), you can make much better use of arrays. Here's one approach:

# This goes into your bash startup file:
declare -a SAVED_ARGS
save_args() {
  SAVED_ARGS=("$@")
}

do_script() {
  /path/to/script.sh "${SAVED_ARGS[@]}" "$@"
}

为了进行说明， script.sh ：

#!/bin/bash
command() { :; }

set -x
command "${@/#/-}"
set +x

例如：

$ save_args x=3 y="a few words from our sponsor"
$ do_script a=3 b="arg2.0 arg2.1"
+ command -x=3 '-y=a few words from our sponsor' -a=3 '-b=arg2.0 arg2.1'
+ :
+ set +x
$ do_script a=42
+ command -x=3 '-y=a few words from our sponsor' -a=42
+ :
+ set +x

在情况下，它并不明显：

In case it's not obvious:

command() { :; }

定义命令称为bash的功能，几乎没做什么（除了调用内置的：它什么都不做），和

defines a bash function called command which does almost nothing (except invoke the builtin : which does nothing), and

"${@/#/-}"

扩展到位置参数，在每一个使​​用的开头插入一个破折号查找和替换替换。该模式＃实际上是一个空的模式，只有在字符串开始处匹配。

expands to the positional parameters, inserting a dash at the beginning of each one use a find-and-replace substitution. The pattern # is actually an empty pattern which only matches at the beginning of the string.

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