Best way to grep substring from a string before a character or string in golang

Question

I got net.Conn.RemoteAddr() as this:

192.168.16.96:64840

I only need IP address without port number

...
str := conn.RemoteAddr().String()
strSlice := strings.Split(str, ":")
ipAddress := strSlice[0]
...

Is there any simple way?

ipAddress := strings.Split(conn.Remoteddr().String(), ":")[0] — GarMan
– GarMan, Commented Mar 16, 2016 at 5:17
@GarMan It still looks ugly.... :( Do I have to wrap these things by my self? — Yi Jiang
– Yi Jiang, Commented Mar 16, 2016 at 5:55
on a side note: OPs and GarMans code wouldn't work with IPv6 — Daniele D
– Daniele D, Commented Mar 16, 2016 at 8:36

sberry · Accepted Answer · 2016-03-17 07:34:42Z

11

You can use net.SplitHostPort, like so

ip, _, err := net.SplitHostPort(conn.RemoteAddr().String())
if err != nil {
    fmt.Println(err)
    return
}
fmt.Println(ip)

Try it on the Playground

To answer OP's question in the comments above, net.SplitHostPort already deals with IPv6. Given the string

net.SplitHostPort("[2001:db8:85a3:0:0:8a2e:370]:7334")

Will work as intended.

answered Mar 16, 2016 at 6:04

sberry

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