执行命令，如Bash的字符串 [英] Execute command as a string in Bash

问题描述

我测试一个简短的bash脚本。我想执行字符串命令。

 ＃！/斌/庆典回声AVR-GCC
$精灵=main.elf
$ C =$的main.c
$ GCC =AVR-GCC -mmcu = ATmega128的-Wall -Os -o $精灵$ C
EVAL $ GCC
回声AVR-GCC做
 

我知道这是丑陋的，所有的，但它不应该执行AVR-GCC命令？
这些错误有以下几种：

  ./ AVR.sh：4号线：= main.elf：命令未找到
./AVR.sh：5号线：= .C：命令未找到
./AVR.sh：6号线：= AVR-GCC -mmcu = ATmega128的-Wall -Os -o：命令未找到
 

解决方案

我不知道你的最终目标是什么，但你可能会改为考虑使用以下更可靠的方法：使用数组在bash。 （我不打算讨论你在你的脚本有几个语法错误。）

不要把你的命令及其参数的字符串像你一样，然后评估字符串（顺便说一句，你的情况中，eval也没用）。我理解你的脚本（这个版本不会给你你所提到的错误，比较您的版本，特别是有对变量赋值没有美元符号）：

 ＃！/斌/庆典回声AVR-GCC
精灵=main.elf
C =main.c中
GCC =AVR-GCC -mmcu = ATmega128的-Wall -Os -o $精灵$ C
EVAL $ GCC
回声AVR-GCC做
 

您会很快遇到问题的时候，比如你遇到空格或搞笑的符号文件（觉得一个名为的;室射频* ）。相反：

 ＃！/斌/庆典回声AVR-GCC
精灵=main.elf
C =main.c中
GCC =AVR-GCC
选项​​=（-mmcu = ATmega128的-Wall - OS）
命令=（$ GCC$ {选项[@]}-o$小精灵，$ C）
＃执行：
$ {命令[@]}
 

试着了解是怎么回事（我可以澄清任何具体点，你会问我），并意识到它是多么安全不是将命令字符串。

I'm testing a short bash script. I'd like to execute a string as a command.

#!/bin/bash

echo "AVR-GCC"
$elf=" main.elf"
$c=" $main.c"
$gcc="avr-gcc -mmcu=atmega128 -Wall -Os -o $elf$c"
eval $gcc
echo "AVR-GCC done"

I know it's ugly and all, but shouldn't it execute the avr-gcc command? The errors are the following:

./AVR.sh: line 4: = main.elf: command not found
./AVR.sh: line 5: = .c: command not found
./AVR.sh: line 6: =avr-gcc -mmcu=atmega128 -Wall -Os -o : command not found

解决方案

I don't know what your final goal is, but you might instead consider using the following more robust way: using arrays in bash. (I'm not going to discuss the several syntax errors you have in your script.)

Don't put your commands and its argument in a string as you did and then eval the string (btw, in your case, the eval is useless). I understand your script as (this version will not give you the errors you mentioned, compare with your version, especially there are no dollar signs for variable assignments):

#!/bin/bash

echo "AVR-GCC"
elf="main.elf"
c="main.c"
gcc="avr-gcc -mmcu=atmega128 -Wall -Os -o $elf $c"
eval $gcc
echo "AVR-GCC done"

You'll very soon run into problems when, for example, you encounter files with spaces or funny symbols (think of a file named ; rm -rf *). Instead:

#!/bin/bash

echo "AVR-GCC"
elf="main.elf"
c="main.c"
gcc="avr-gcc"
options=( "-mmcu=atmega128" "-Wall" -"Os" )
command=( "$gcc" "${options[@]}" -o "$elf" "$c" )
# execute it:
"${command[@]}"

Try to understand what's going on here (I can clarify any specific points you'll ask me to), and realize how much safer it is than putting the command in a string.

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