Linux 在 Bash 中以字符串形式执行命令
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Execute command as a string in Bash
提问by erbal
I'm testing a short bash script. I'd like to execute a string as a command.
我正在测试一个简短的 bash 脚本。我想将字符串作为命令执行。
#!/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:
我知道这很丑陋，但它不应该执行 avr-gcc 命令吗？错误如下：
./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
采纳答案by gniourf_gniourf
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.)
我不知道你的最终目标是什么，但你可以考虑使用以下更强大的方式：在 bash 中使用数组。（我不打算讨论脚本中的几个语法错误。）
Don't put your commands and its argument in a string as you did and then evalthe 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):
不要像之前那样将命令及其参数放在字符串中，然后eval是字符串（顺便说一句，在您的情况下， eval 没用）。我理解你的脚本（这个版本不会给你你提到的错误，与你的版本比较，特别是变量赋值没有美元符号）：
#!/bin/bash
echo "AVR-GCC"
elf="main.elf"
c="main.c"
gcc="avr-gcc -mmcu=atmega128 -Wall -Os -o $elf $c"
eval $gcc
echo "AVR-GCC done"
You'll very soon run into problems when, for example, you encounter files with spaces or funny symbols (think of a file named ; rm -rf *). Instead:
例如，当您遇到带有空格或有趣符号的文件（想想名为 的文件; rm -rf *）时，您很快就会遇到问题。反而：
#!/bin/bash
echo "AVR-GCC"
elf="main.elf"
c="main.c"
gcc="avr-gcc"
options=( "-mmcu=atmega128" "-Wall" -"Os" )
command=( "$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.
试着理解这里发生了什么（我可以澄清你要我做的任何具体点），并意识到它比将命令放在字符串中要安全得多。
回答by Some programmer dude
You don't use the dollar sight when creating variables, only when accessing them.
创建变量时不使用美元视线，仅在访问它们时使用。
So change
所以改变
$elf=" main.elf"
$c=" $main.c"
$gcc="avr-gcc -mmcu=atmega128 -Wall -Os -o $elf$c"
to
到
elf=" main.elf"
c=" $main.c"
gcc="avr-gcc -mmcu=atmega128 -Wall -Os -o $elf$c"
