escchar = $(subst $(squote),'\$(squote)',$1)
时间: 2024-01-19 16:04:14 浏览: 21
这是一个Makefile中的函数,作用是将变量中的单引号替换为转义后的单引号。具体来说,$1表示传入的第一个参数(即需要替换的变量),$(squote)表示单引号。函数中的subst函数将变量中的单引号替换为'\$(squote)',其中\是转义符,表示后面的字符是需要转义的。最终返回替换后的字符串。
相关问题
escchar = $(subst $(squote),'\$(squote)',$1) give me an example based on this
Sure, here's an example:
Suppose we have a variable `message` with the value `It's a beautiful day!`. If we want to use this variable in a makefile command, we need to escape the single quote character (`'`) so that the command is properly interpreted. We can do this using the `subst` function like so:
```
escaped_message = $(subst $(squote),'\$(squote)',$(message))
```
This will replace any instances of the `$(squote)` variable (which is set to a single quote character) in the `message` variable with `'\$(squote)'`, effectively escaping the single quotes.
So, in this example, `escaped_message` would have the value `It'\$(squote)s a beautiful day!`. We can then use this variable in a makefile command without any issues.
Suppose we have a variable message with the value It's a beautiful day!. escaped_message = $(subst $(squote),'$(squote)',$(message)) shouldn't the result be It'$(squote)'s a beautiful day! ? If so, the return result will have two single quote, isn't wrong?
Yes, you are correct. The result of the command `escaped_message = $(subst $(squote),'$(squote)',$(message))` will indeed have two single quotes, which is not what we want.
A better way to escape the single quote in `$(message)` is to replace it with a backslash followed by a single quote (`\'`), like this:
```
escaped_message = $(subst ','\'',$(message))
```
This will replace all single quotes in `$(message)` with the escaped sequence `\'`, which represents a single quote. The resulting value of `escaped_message` will be `It\'s a beautiful day!`, which correctly escapes the single quote without adding any extra quotes.
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