一个我无法弄清楚的正则表达式问题（负面看后方）

how do i do this with regex?

我如何用正则表达式做到这一点?

i want to match this string: -myString

我想匹配这个字符串:-myString

but i don't want to match the -myString in this string: --myString

但我不想匹配此字符串中的-myString: - myString

myString is of course anything.

myString当然是任何东西。

is it even possible?

它甚至可能吗?

EDIT:

here's a little more info with what i got so far since i've posted a question:

这里有一些关于我到目前为止所得到的信息,因为我发布了一个问题:

string to match:
some random stuff here -string1, --string2, other stuff here
regex:
(-)([\w])*

This regex returns me 3 matches: -string1, - and -string2

这个正则表达式返回3个匹配:-string1, - 和-string2

ideally i'd like it to return me only the -string1 match

理想情况下,我希望它只返回-string1匹配

6 个解决方案

#1

Assuming your regex engine supports (negative) lookbehind:

假设你的正则表达式引擎支持(负面)lookbehind:

/(?<!-)-myString/

Perl does, Javascript doesn't, for example.

Perl确实如此,Javascript没有。

#2

You want to match a string that starts with a single dash, but not one that has multiple dashes?

您希望匹配以单个破折号开头的字符串,但不匹配具有多个破折号的字符串?

^-[^-]

Explanation:

^ Matches start of string
- Matches a dash
[^-] Matches anything but a dash

#3

/^[^-]*-myString/

Testing:

[~]$ echo -myString | egrep -e '^[^-]*-myString'
-myString
[~]$ echo --myString | egrep -e '^[^-]*-myString'
[~]$ echo test--myString | egrep -e '^[^-]*-myString'
[~]$ echo test --myString | egrep -e '^[^-]*-myString'
[~]$ echo test -myString | egrep -e '^[^-]*-myString'
test -myString

#4

based on the last edit, I guess the following expression would work better

根据上次编辑,我猜以下表达式会更好

\b\-\w+

#5

[^-]{0,1}-[^\w-]+

#6

Without using any look-behinds, use:

不使用任何外观,使用:

(?:^|(?:[\s,]))(?:\-)([^-][a-zA-Z_0-9]+)

Broken out:

(
  ?:^|(?:[\s,])        # Determine if this is at the beginning of the input,
                       # or is preceded by whitespace or a comma
)
(
  ?:\-                 # Check for the first dash
)
(
  [^-][a-zA-Z_0-9]+    # Capture a string that doesn't start with a dash
                       # (the string you are looking for)
)

#1