CODEWITHSUNDEEP
regexgo
Sankar
Sankar

Reputation: 6522

Golang regexp to match multiple patterns between keyword pairs

I have a string which has two keywords: "CURRENT NAME(S)" and "NEW NAME(S)" and each of these keywords are followed by a bunch of words. I want to extract those set of words beyond each of these keywords. To elaborate with a code:

    s := `"CURRENT NAME(S)
 Name1, Name2",,"NEW NAME(S)
NewName1,NewName2"`
    re := regexp.MustCompile(`"CURRENT NAME(S).*",,"NEW NAME(S).*"`)

    segs := re.FindAllString(s, -1)
    fmt.Println("segs:", segs)

    segs2 := re.FindAllStringSubmatch(s, -1)
    fmt.Println("segs2:", segs2)

As you can see, the string 's' has the input. "Name1,Name2" is the current names list and "NewName1, NewName2" is the new names list. I want to extract these two lists. The two lists are separated by a comma. Each of the keywords are beginning with a double quote and their reach ends, when their corresponding double quote ends.

What is the way to use regexp such that the program can print "Name1, Name2" and "NewName1,NewName2" ?

Upvotes: 4

Views: 15731

Answers (3)

dmitris
dmitris

Reputation: 1491

For a fixed format like in the example, you can also avoid regular expressions and perform explicit parsing as in this example - https://play.golang.org/p/QDIyYiWJHt:

package main

import (
    "fmt"
    "strings"
)

func main() {
    s := `"CURRENT NAME(S)
 Name1, Name2",,"NEW NAME(S)
NewName1,NewName2"`

    names := []string{}
    parts := strings.Split(s, ",,")
    for _, part := range parts {
        part = strings.Trim(part, `"`)
        part = strings.TrimPrefix(part, "CURRENT NAME(S)")
        part = strings.TrimPrefix(part, "NEW NAME(S)")
        part = strings.TrimSpace(part)
        names = append(names, part)
    }
    fmt.Println("Names:")
    for _, name := range names {
        fmt.Println(name)
    }
}

Output:

Names:
Name1, Name2
NewName1,NewName2

It uses a few more lines of code but may make it easier to understand the processing logic at a first glance.

Upvotes: 0

Wiktor Stribiżew
Wiktor Stribiżew

Reputation: 626747

The issue with your regex is that the input string contains newline symbols, and . in Go regex does not match a newline. Another issue is that the .* is a greedy pattern and will match as many symbols as it can up to the last second keyword. Also, you need to escape parentheses in the regex pattern to match the ( and ) literal symbols.

The best way to solve the issue is to change .* into a negated character class pattern [^"]* and place it inside a pair of non-escaped ( and ) to form a capturing group (a construct to get submatches from the match).

Here is a Go demo:

package main

import (
    "fmt"
    "regexp"
)

func main() {
    s := `"CURRENT NAME(S)
 Name1, Name2",,"NEW NAME(S)
NewName1,NewName2"`
    re := regexp.MustCompile(`"CURRENT NAME\(S\)\s*([^"]*)",,"NEW NAME\(S\)\s*([^"]*)"`)

    segs2 := re.FindAllStringSubmatch(s,-1)
    fmt.Printf("segs2: [%s; %s]", segs2[0][1], segs2[0][2])
}

Now, the regex matches:

  • "CURRENT NAME\(S\) - a literal string "CURRENT NAME(S)`
  • \s* - zero or more whitespaces
  • ([^"]*) - Group 1 capturing 0+ chars other than "
  • ",,"NEW NAME\(S\) - a literal string ",,"NEW NAME(S)
  • \s* - zero or more whitespaces
  • ([^"]*) - Group 2 capturing 0+ chars other than "
  • " - a literal "

Upvotes: 4

abhink
abhink

Reputation: 9126

If your input doesn't change then the simplest way would be to use submatches (groups). You can try something like this:

// (?s) is a flag that enables '.' to match newlines
var r = regexp.MustCompile(`(?s)CURRENT NAME\(S\)(.*)",,"NEW NAME\(S\)(.*)"`)
fmt.Println(r.MatchString(s))
m := r.FindSubmatch([]byte(s)) // FindSubmatch requires []byte

for _, match := range m {
    s := string(match)
    fmt.Printf("Match - %d: %s\n", i, strings.Trim(s, "\n")) //remove the newline
}

Output: (Note that the first match is the entire input string because it completely matches the regex (https://golang.org/pkg/regexp/#Regexp.FindSubmatch)

Match - 0: CURRENT NAME(S)
Name1, Name2",,"NEW NAME(S)
NewName1,NewName2"
Match - 1: Name1, Name2
Match - 2: NewName1,NewName2

Example: https://play.golang.org/p/0cgBOMumtp

Upvotes: 1

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