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regex: what does [^ ] mean?

regex: what does [^ ] mean?# Unix - 噫吁兮，危乎高哉

f*y2003-02-26 08:02

1 楼

s/^([^ ]+) +([^ ]+)/$2 $1/;
the expression above is to swap the first two words..
what does [^ ] mean? it matches a space at the
first charactor position of a string?

T*r2003-02-26 08:02

2 楼

[^ ] means NOT space.

【在 f***y 的大作中提到】

: s/^([^ ]+) +([^ ]+)/$2 $1/;
: the expression above is to swap the first two words..
: what does [^ ] mean? it matches a space at the
: first charactor position of a string?

f*y2003-02-26 08:02

3 楼

Thank you very much for you answer.
$testswap = "one two three";
$testswap =~ s/^(.+) +(.+)/$2 $1/;
print "$testswap\n";
the screen output is: "three one two"
why? I expected "two one three"..
Thanks.

【在 T********r 的大作中提到】

: [^ ] means NOT space.

c*j2003-02-26 08:02

4 楼

This is confusing, you use "." to match any character including " "
and excluding "\n", so every parts of your string will be treated as $1
until it meets the last non-space part (from your " +").
say,
s/^(.+) +(.+)/
1. anything from beginning should be assigned to $1 from code "/^(.+)"
2. anything to the end should be assigned to $2 from code "(.+)/"
3. there should be some space between $1 and $2 from code " +"
result: $1 == "one two"
$2 == "three"

【在 f***y 的大作中提到】

: Thank you very much for you answer.
: $testswap = "one two three";
: $testswap =~ s/^(.+) +(.+)/$2 $1/;
: print "$testswap\n";
: the screen output is: "three one two"
: why? I expected "two one three"..
: Thanks.

f*y2003-02-26 08:02

5 楼

you are right..
Thank you very much.

【在 c****j 的大作中提到】

:
: This is confusing, you use "." to match any character including " "
: and excluding "\n", so every parts of your string will be treated as $1
: until it meets the last non-space part (from your " +").
: say,
: s/^(.+) +(.+)/
: 1. anything from beginning should be assigned to $1 from code "/^(.+)"
: 2. anything to the end should be assigned to $2 from code "(.+)/"
: 3. there should be some space between $1 and $2 from code " +"
: result: $1 == "one two"

p*s2003-02-26 08:02

6 楼

Regexp matching is greedy, that is, it will try to match
the longest pattern.
Thus, "^(.+) +" matches "one two ", and $1 is "one two".
The next "(.+)" matches "three", and $2 is "three".

【在 f***y 的大作中提到】

f*y2003-02-26 08:02

7 楼

that's right.. i forgot it's greedy.
Thank you.

【在 p****s 的大作中提到】

:
: Regexp matching is greedy, that is, it will try to match
: the longest pattern.
: Thus, "^(.+) +" matches "one two ", and $1 is "one two".
: The next "(.+)" matches "three", and $2 is "three".