bash:将字符串变量解释为文件名/路径 [英] bash: interpret string variable as file name/path

问题描述

我的bash脚本以字符串形式接收文件名(或相对路径)，但是必须从该文件中读取.如果我直接在脚本中将文件名声明为文字(不带引号)，则只能从文件名中读取...这对于参数来说是不可能的，因为它们是隐式的字符串开头.观察:

My bash script receives a filename (or relative path) as a string, but must then read from that file. I can only read from a filename if I declare it as a literal directly in the script (without quotes)...which is impossible for arguments since they are implicitly strings to begin with. Observe:

a="~/test.txt"
#Look for it
if [[ -a $a ]] ; then
    echo "A Found it"
else
    echo "A Error"
fi
#Try to use it
while read line; do
    echo $line
done < $a

b='~/test.txt'
#Look for it
if [[ -a $b ]] ; then
    echo "B Found it"
else
    echo "B Error"
fi
#Try to use it
while read line; do
    echo $line
done < $b

c=~/test.txt
#Look for it
if [[ -a $c ]] ; then
    echo "C Found it"
else
    echo "C Error"
fi
#Try to use it
while read line; do
    echo $line
done < $c

收益:

A Error
./test.sh: line 10: ~/test.txt: No such file or directory
B Error
./test: line 12: ~/test.txt: No such file or directory
C Found it
Hello

如上所述，我无法将命令行参数传递给上述例程，因为我得到的行为与引用的字符串相同.

As stated above, I can't pass a command line argument to the routines above since I get the same behavior that I get on the quoted strings.

推荐答案

这是~-扩展规则的一部分. Bash手册中明确指出，~用引号引起来时，不会执行此扩展.

This is part of the rules of ~-expansion. It is clearly stated in the Bash manual that this expansion is not performed when the ~ is quoted.

不要引用~.

file=~/path/to/file

如果您需要引用其余文件名:

If you need to quote the rest of the filename:

file=~/"path with spaces/to/file"

(这在各种花园中都是完全合法的.)

(This is perfectly legal in a garden-variety shell.)

使用$HOME代替~.

file="$HOME/path/to/file"

BTW:Shell变量类型

您似乎对shell变量的类型有些困惑.

BTW: Shell variable types

You seem to be a little confused about the types of shell variables.

一切都是字符串.

重复直到它陷入:一切都是字符串.(除了整数，但它们大多是在字符串AFAIK之上的hack.和数组，但它们是字符串的数组.)

Repeat until it sinks in: Everything is a string. (Except integers, but they're mostly hacks on top of strings AFAIK. And arrays, but they're arrays of strings.)

这是一个外壳程序字符串:"foo". "42"也是如此. 42也是如此. foo也是如此.如果您不需要引用任何内容，则最好不要引用.谁想输入"ls" "-la" "some/dir"?

This is a shell string: "foo". So is "42". So is 42. So is foo. If you don't need to quote things, it's reasonable not to; who wants to type "ls" "-la" "some/dir"?

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