Java: replace() the n pipe delimiter starting at the end with a regex

Question

I'm trying to replace the first "|" but by starting by the end of the string:

usr/bin/pipe|pipe|name|28|-rwxr-xr-x|root:root||46711b361edd4512814d9b367ae765f42a71d729708b3f2e162acb8f64592610|

my file name is pipe|pipe|name and i want my regex to return me usr/bin/pipe|pipe|name

I've begin by this regex: .([^\|]*)$ but I don't know how to go further in the pipes : https://regex101.com/r/ttbiab/3

And in Java:

String strLine = "usr/bin/pipe|pipe|name|28|-rwxr-xr-x|root:root||46711b361edd4512814d9b367ae765f42a71d729708b3f2e162acb8f64592610|";
strLine = strLine.replaceAll(".([^\\|]*)$", "[:124:]");
System.out.println("strLine : " + strLine);

Can you provide examples? Not sure if you mean the first pipe in the string or the last pipe. — John
– John, Commented Apr 23, 2019 at 14:18
What command is generating the string that you're trying to parse? Based on what you've shown, a filename might theoretically contain no pipes, one pipe, or multiple pipes, so you'll need to use something besides just the pipes to base your regex on. — Jordan
– Jordan, Commented Apr 23, 2019 at 14:24
I want to handle files with pipes ;) it's a scan agent who generates me a file with all the packages I've intalled on a linux machine — TheSmartMonkey
– TheSmartMonkey, Commented Apr 23, 2019 at 14:28

Jordan · Accepted Answer · 2019-04-23 17:10:49Z

Based on your comments, it looks like you don't know how many pipes will be in the filename, but you do know how many pipes are in the input string that aren't in the filename. In this case, regex may not be the best approach. There are a couple of different ways to do this, but perhaps one of the easiest to understand and maintain would be to split the String, and then recombine it with replacements where applicable:

String input = "usr/bin/pipe|pipe|name|28|-rwxr-xr-x|root:root||46711b361edd4512814d9b367ae765f42a71d729708b3f2e162acb8f64592610|";
String pipeReplacement = ":124:";
int numberOfPipesToKeep = 7;

String[] split = input.split("\\|");
StringBuilder sb = new StringBuilder();
for (int i = 0; i < split.length; i++) {
    sb.append(split[i]);
    if (i < split.length - numberOfPipesToKeep) {
        sb.append(pipeReplacement);
    } else {
        sb.append("|");
    }
}

String output = sb.toString();
System.out.println(output);

The above sample handles any number of pipes, is pretty configurable, and is (in my opinion) a lot easier to understand and debug than trying to use regular expressions.

Wai Ha Lee · Accepted Answer · 2019-04-23 15:30:40Z

0

You can try something like this [\|]([^\|]*[\|]){5}$. It matches the pipe count of 5 followed by first pipe from the ends.

edited Apr 23, 2019 at 15:30

Wai Ha Lee

8,856102 gold badges61 silver badges100 bronze badges

answered Apr 23, 2019 at 15:20

Akshay Mishra

1892 silver badges9 bronze badges

Comments

The fourth bird · Accepted Answer · 2019-04-23 17:55:07Z

If there is a fixed number of 6 pipes until the end of the string, and you want to select the individual pipes before that to replace them, you could make use of \G to assert the position at the previous match and use a lookahead to assert that what is on the right is 6 times not a pipe followed by a pipe.

(?:([^\|]*)|\G(?!^))\|([^|]*)(?=(?:[^|]*\|){6})

In Java:

String regex = "(?:([^\\|]*)|\\G(?!^))\\|([^|]*)(?=(?:[^|]*\\|){6})";

(?: Non capturing group
- ([^\|]*) Capture in group 1 matching not a pipe 0+ times using a negated character class
- | OR
- \G(?!^) Assert position at the end of the previous match, not at the start
) Close non capturing group
\|([^|]*) Match a pipe and capture in group 2 match 0+ times not a pipe
(?= Non capturing group
- (?:[^|]*\|){6} Positive lookahead, assert what is on the right is 6 times not a pipe followed by a pipe
) Close non capturing group

Regex demo | Java demo

If you want to replace the pipe with for example #, then use the 2 capturing groups:

$1#$2

Collectives™ on Stack Overflow

Java: replace() the n pipe delimiter starting at the end with a regex

3 Answers 3

Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related