:置き換える:
(^|[^\\])(\\{2})*(?=\$)
を\\
続く(先読みを除く)マッチしたテキスト全体、と。 Perlで
イラスト:Javaを使用し
$ perl -pe 's,(^|[^\\])(\\{2})*(?=\$),$&\\,g'
"$ Find the $ to \$ escape \\$ or not \\\$ escape \\\\$ like here $" # in...
"\$ Find the \$ to \$ escape \\\$ or not \\\$ escape \\\\\$ like here \$" # out
"\$ Find the \$ to \$ escape \\\$ or not \\\$ escape \\\\\$ like here \$" # in...
"\$ Find the \$ to \$ escape \\\$ or not \\\$ escape \\\\\$ like here \$" # out
、全体のテキストマッチが$0
です。サンプルコード:
// package declaration skipped
import java.util.regex.Pattern;
public final class TestMatch
{
private static final Pattern p
= Pattern.compile("(^|[^\\\\])(\\\\{2})*(?=\\$)");
public static void main(final String... args)
{
String input = "\"$ Find the $ to \\$ escape \\\\$ or not \\\\\\$ "
+ "escape \\\\\\\\$ like here $\"";
System.out.println(input);
// Apply a first time
input = p.matcher(input).replaceAll("$0\\\\");
System.out.println(input);
// Apply a second time: the input should not be altered
input = p.matcher(input).replaceAll("$0\\\\");
System.out.println(input);
System.exit(0);
}
}
出力:
"$ Find the $ to \$ escape \\$ or not \\\$ escape \\\\$ like here $"
"\$ Find the \$ to \$ escape \\\$ or not \\\$ escape \\\\\$ like here \$"
"\$ Find the \$ to \$ escape \\\$ or not \\\$ escape \\\\\$ like here \$"
使用正規表現について少し説明が順序である:
# begin regex:
( # start group
^ # find the beginning of input,
| # or
[^\\] # one character which is not the backslash
) # end group
# followed by
( # start group
\\{2} # exactly two backslashes
) # end group
* # zero or more times
# and at that position,
(?= # begin lookahead
\$ # find a $
) # end lookahead
# end regex
ここでは、実際に完全にするために正規表現での位置でありますエンジンは一致するテキスト(<>
で表されます)とカーソル位置(|
によって象徴されます):
# Before first run:
|"$ Find the $ to \$ escape \\$ or not \\\$ escape \\\\$ like here $"
# First match
"<>|$ Find the $ to \$ escape \\$ or not \\\$ escape \\\\$ like here $"
# Second match
"$ Find the <>|$ to \$ escape \\$ or not \\\$ escape \\\\$ like here $"
# Third match
"$ Find the $ to \$ escape <\\>|$ or not \\\$ escape \\\\$ like here $"
# Fourth match
"$ Find the $ to \$ escape \\$ or not \\\$ escape <\\\\>|$ like here $"
# From now on, there is no match
出典
2012-01-06 13:10:41
fge