Can these two regex expressions ever give a different result?
这两个正则表达式可以给出不同的结果吗?
perl -pe 's/.*c//s'
perl -pe的/.* c // s'
perl -0777 -pe 's/.*c//s'
perl -0777 -pe的/.* c // s'
Where the .*c can be replaced with anything..
哪里。* c可以替换任何东西..
In the .*c case the result is the same
在。* c的情况下,结果是相同的
$ echo -e 'a\nb\nc\nd' | perl -pe 's/.*c//s'
a
b
d
$ echo -e 'a\nb\nc\nd' | perl -0777 -pe 's/.*c//'
a
b
d
And the question re the difference between the regexes, is where what is echoed can be replaced with anything too.
问题是正则表达式之间的差异,回声的东西也可以用任何东西代替。
Are -0777 and /s interchangeable?
-0777和/ s是否可以互换?
And is it pointless to do both -0777 with /s ?
使用/ s同时执行-0777是没有意义的吗?
2 个解决方案
#1
3
They mean completely different things and are not interchangeable, even though in some cases they can have the same result.
它们意味着完全不同的东西,并且不可互换,即使在某些情况下它们可以具有相同的结果。
-
/smakes.match all characters (including linebreaks); without it.usually means[^\n] -
-0777means read the whole file at once; without it the file is read line by line
/ s使。匹配所有字符(包括换行符);没有它 。通常意味着[^ \ n]
-0777表示一次读取整个文件;没有它,文件将逐行读取
/s doesn't change how the input is parsed, -0 does.
/ s不会改变解析输入的方式,-0会这样做。
-0777 is usually only useful if you are matching across several lines (in which case /s can be helpful). If you are matching line by line, then whether you use /s or not doesn't matter.
-0777通常仅在您跨多行匹配时才有用(在这种情况下/ s可能会有所帮助)。如果你逐行匹配,那么你是否使用/ s并不重要。
For example (using your example), if you would like to remove everything up to the last c, including all the lines, you could use:
例如(使用您的示例),如果您想删除最后一个c的所有内容,包括所有行,您可以使用:
echo -e 'a\nb\nc\nd' | perl -0777 -pe 's/.*c//s'
Output:
d
#2
2
Qtax gives a good answer, i'm just going to include some examples to demonstrate they're not the same or even effectively the same.
Qtax给出了一个很好的答案,我只是要包含一些例子来证明它们不相同甚至有效。
These two
$ echo -e 'a\nb\nc\nd' | perl -pe 's/./o/s'
o
o
o
o
$ echo -e 'a\nb\nc\nd' | perl -0777 -pe 's/./o/'
o
b
c
d
These two
$ echo -e 'aa\nbb\ncc\ndd' | perl -0777 -pe 's/./o/'
oa
bb
cc
dd
$ echo -e 'aa\nbb\ncc\ndd' | perl -pe 's/./o/s'
oa
ob
oc
od
These two
$ echo -e 'aa\nbb\ncc\ndd' | perl -pe 's/./o/sg'
oooooooooooo
$ echo -e 'aa\nbb\ncc\ndd' | perl -0777 -pe 's/./o/g'
oo
oo
oo
oo
Those all demonstrate that -0777 and /s are not the same.
这些都表明-0777和/ s不一样。
#1
3
They mean completely different things and are not interchangeable, even though in some cases they can have the same result.
它们意味着完全不同的东西,并且不可互换,即使在某些情况下它们可以具有相同的结果。
-
/smakes.match all characters (including linebreaks); without it.usually means[^\n] -
-0777means read the whole file at once; without it the file is read line by line
/ s使。匹配所有字符(包括换行符);没有它 。通常意味着[^ \ n]
-0777表示一次读取整个文件;没有它,文件将逐行读取
/s doesn't change how the input is parsed, -0 does.
/ s不会改变解析输入的方式,-0会这样做。
-0777 is usually only useful if you are matching across several lines (in which case /s can be helpful). If you are matching line by line, then whether you use /s or not doesn't matter.
-0777通常仅在您跨多行匹配时才有用(在这种情况下/ s可能会有所帮助)。如果你逐行匹配,那么你是否使用/ s并不重要。
For example (using your example), if you would like to remove everything up to the last c, including all the lines, you could use:
例如(使用您的示例),如果您想删除最后一个c的所有内容,包括所有行,您可以使用:
echo -e 'a\nb\nc\nd' | perl -0777 -pe 's/.*c//s'
Output:
d
#2
2
Qtax gives a good answer, i'm just going to include some examples to demonstrate they're not the same or even effectively the same.
Qtax给出了一个很好的答案,我只是要包含一些例子来证明它们不相同甚至有效。
These two
$ echo -e 'a\nb\nc\nd' | perl -pe 's/./o/s'
o
o
o
o
$ echo -e 'a\nb\nc\nd' | perl -0777 -pe 's/./o/'
o
b
c
d
These two
$ echo -e 'aa\nbb\ncc\ndd' | perl -0777 -pe 's/./o/'
oa
bb
cc
dd
$ echo -e 'aa\nbb\ncc\ndd' | perl -pe 's/./o/s'
oa
ob
oc
od
These two
$ echo -e 'aa\nbb\ncc\ndd' | perl -pe 's/./o/sg'
oooooooooooo
$ echo -e 'aa\nbb\ncc\ndd' | perl -0777 -pe 's/./o/g'
oo
oo
oo
oo
Those all demonstrate that -0777 and /s are not the same.
这些都表明-0777和/ s不一样。