Golang regexp to match string until a given sequence of characters

Question

I have a string that could have a -name followed by value (that can have spaces) and there could also be -descr after that followed by a value (the -descr followed by value may nor may not be there):

Example strings:

runcmd -name abcd xyz -descr abc def

or

runcmd -name abcd xyz

With Go language, how do I write regexp, that returns me the string before -descr if it exists. so, for both examples above, the result should be:

runcmd -name abcd xyz

I was trying:

regexp.MustCompile(`(-name ).+?=-descr`)

But, that did not return any match. I wanted to know the correct regexp to get the string up until -descr if it exists

When you say something "does not work", it's important to explain how - error, incorrect behavior (and specify what), etc. Just from looking at the code, however, your regex is looking for a string with an = in it, but you exemplars do not contain that character. — Adrian
– Adrian, Commented Jan 9, 2019 at 16:24
If you can use a capturing group, try ^(.*? -name.*?)(?: *-descr|$) demo — The fourth bird
– The fourth bird, Commented Jan 9, 2019 at 16:27
Should -descr be there? Because it is not in the second example. — The fourth bird
– The fourth bird, Commented Jan 9, 2019 at 16:30
@Thefourthbird, will this capturing group work with Golang? Can you tell the syntax to use with regex.MustCompile? — user1892775
– user1892775, Commented Jan 9, 2019 at 16:31

The fourth bird · Accepted Answer · 2019-01-09 23:24:46Z

1

You could capturin first part with -name in a group, then match what is in between and use an optional second capturing group to match -descr and what follows.

Then you could use the capturing groups when creating the desired result.

^(.*? -name\b).*?(-descr\b.*)?$

Regex demo | Go demo

For example:

s := "runcmd -name abcd xyz -descr abc def"
re1 := regexp.MustCompile(`^(.*? -name\b).*?(-descr\b.*)?$`)
result := re1.FindStringSubmatch(s)
fmt.Printf(result[1] + "..." + result[2])

Result:

runcmd -name...-descr abc def

edited Jan 9, 2019 at 23:24

answered Jan 9, 2019 at 16:40

The fourth bird

165k16 gold badges61 silver badges75 bronze badges

Sign up to request clarification or add additional context in comments.

11 Comments

user1892775 Over a year ago

Is it possible to modify this so the first group only contains uptil -name? The reason is, I would eventually need to do something like re1.ReplaceAllString(s, "$1"+"...."+" ")), so I can return the original string just with the value of -name replaced with ...., so the output string becomes runcmd -name .... -descr abc def which is the final goal

The fourth bird Over a year ago

@user1892775 To get only the first group you could use ^(.*? -name) demo. In that case you could also use just a match instead ^.*? -name demo and it could look like this Go demo

user1892775 Over a year ago

Not sure, if I was clear enough, I want to modify the regexp so that s := "runcmd -name abcd xyz -descr abc def" re1 := regexp.MustCompile(regexp) fmt.Println(re1.ReplaceAllString(s, "$1"+"...."+" ")) should be `runcmd -name .... -descr abc def'

user1892775 Over a year ago

If you could share an example which would give that output (the string with value for -name replaced with ....) as indicated in the code above, that would really help

The fourth bird Over a year ago

@user1892775 Do you mean like this using 2 capturing groups? ideone.com/vOTdLz

|

Stuart Moore · Accepted Answer · 2019-01-09 16:31:18Z

0

By "Does not work", do you mean it doesn't match anything, or just not what you expect?

https://regex101.com/ is generally very helpful when testing regular expressions.

I do not believe there's a simple way to achieve what you want. Things become a lot simpler if we can assume the text betweeen -name and -descr doesn't contain any - in which case, regex.MustCompile(`-name ([^-]*)`) should work

With this kind of thing, often it's easier and clearer to use 2 regular expressions. So the first strips -descr and anything following it, and the first matches -name and all subsequent characters.

answered Jan 9, 2019 at 16:31

Stuart Moore

8208 silver badges33 bronze badges

1 Comment

user1892775 Over a year ago

Text betweeen -name and -descr doesn't contain any -

Peter · Accepted Answer · 2019-01-09 17:46:03Z

0

You are not dealing with a regular language here, so there is no reason to bust out the (slow) regexp engine. The strings package is quite enough:

package main

import (
    "fmt"
    "strings"
    "unicode"
)

func main() {
    fmt.Printf("%q\n", f("runcmd -name abcd xyz -descr abc def"))
    fmt.Printf("%q\n", f("runcmd -name abcd xyz"))
    fmt.Printf("%q\n", f("-descr abc def"))
}

func f(s string) string {
    if n := strings.Index(s, "-descr"); n >= 0 {
        return strings.TrimRightFunc(s[:n], unicode.IsSpace)
    }
    return s
}

// Output:
// "runcmd -name abcd xyz"
// "runcmd -name abcd xyz"
// ""

Try it on the playground: https://play.golang.org/p/RFC65CYe6mp

answered Jan 9, 2019 at 17:46

Peter

32.1k6 gold badges57 silver badges68 bronze badges

Collectives™ on Stack Overflow

Golang regexp to match string until a given sequence of characters

3 Answers 3

11 Comments

1 Comment

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

11 Comments

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related