txeh

Etc Hosts Management Utility & Go Library

/etc/hosts Management

It is easy to open your /etc/hosts file in text editor and add or remove entries. However, if you make heavy use of /etc/hosts for software development or DevOps purposes, it can sometimes be difficult to automate and validate large numbers of host entries.

txeh was initially built as a golang library to support kubefwd, a Kubernetes port-forwarding utility utilizing /etc/hosts heavily, to associate custom hostnames with multiple local loopback IP addresses and remove these entries when it terminates.

A computer's /etc/hosts file is a powerful utility for developers and system administrators to create localized, custom DNS entries. This small go library and utility were developed to encapsulate the complexity of working with /etc/hosts directly by providing a simple interface for adding and removing entries in a /etc/hosts file.

Features:

• Thread-safe operations (mutex-protected for concurrent use)
• IPv4 and IPv6 support
• CIDR range operations for bulk add/remove
• Preserves comments and file formatting
• Cross-platform (Linux, macOS, Windows)

txeh Utility

Install

MacOS homebrew users can brew install txn2/tap/txeh, otherwise see releases for packages and binaries for a number of distros and architectures including Windows, Linux and Arm based systems.

Install with go install

When installing with Go please use the latest stable Go release. At least go1.24 or greater is required.

To install use: go install github.com/txn2/txeh/txeh@master

If you are building from a local source clone, use go install ./txeh from the top-level directory of the clone.

go install will typically put the txeh binary inside the bin directory under go env GOPATH, see Go’s Compile and install packages and dependencies for more on this. You may need to add that directory to your $PATH if you encounter the error txeh: command not found after installation, you can find a guide for adding a directory to your PATH at https://gist.github.com/nex3/c395b2f8fd4b02068be37c961301caa7#file-path-md.

Compile and run from source

dependencies are vendored:

go run ./txeh/txeh.go

Use

The txeh CLI application allows command line or scripted access to /etc/hosts file modification.

Example CLI Usage:

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Add, remove and re-associate hostname entries in your /etc/hosts file.
Read more including usage as a Go library at https://github.com/txn2/txeh

Usage:
  txeh [flags]
  txeh [command]

Available Commands:
  add         Add hostnames to /etc/hosts
  completion  Generate the autocompletion script for the specified shell
  help        Help about any command
  list        List hostnames or IP addresses
  remove      Remove a hostname or ip address
  show        Show hostnames in /etc/hosts
  version     Print the version number of txeh


Flags:
  -d, --dryrun                   dry run, output to stdout (ignores quiet)
  -h, --help                     help for txeh
  -m, --max-hosts-per-line int   Max hostnames per line (0=auto, -1=unlimited, >0=explicit)
  -q, --quiet                    no output
  -r, --read string              (override) Path to read /etc/hosts file.
  -w, --write string             (override) Path to write /etc/hosts file.

# point the hostnames "test" and "test.two" to the local loopback
sudo txeh add 127.0.0.1 test test.two

# remove the hostname "test"
sudo txeh remove host test

# remove multiple hostnames
sudo txeh remove host test test2 test.two

# remove an IP address and all the hosts that point to it
sudo txeh remove ip 93.184.216.34

# remove multiple IP addresses
sudo txeh remove ip 93.184.216.34 127.1.27.1

# remove CIDR ranges
sudo txeh remove cidr 93.184.216.0/24 127.1.27.0/28

# quiet mode will suppress output
sudo txeh remove ip 93.184.216.34 -q

# dry run will print a rendered /etc/hosts with your changes without
# saving it.
sudo txeh remove ip 93.184.216.34 -d

# use quiet mode and dry-run to direct the rendered /etc/hosts file
# to another file
sudo txeh add 127.1.27.100 dev.example.com -q -d > hosts.test

# specify an alternate /etc/hosts file to read. writing will
# default to the specified read path.
txeh add 127.1.27.100 dev2.example.com -q -r ./hosts.test

# specify a separate read and write path
txeh add 127.1.27.100 dev3.example.com -r ./hosts.test -w ./hosts.test2

Comments

txeh supports inline comments on host entries, useful for tracking which tool or purpose added specific entries (e.g., docker, development environments).

How Comments Work

Comments use the standard hosts file format: IP HOSTNAME [HOSTNAME...] # comment

Key behavior:

• Comments are used for grouping: hosts with the same IP AND same comment are placed on the same line
• Hosts added without a comment only match lines without a comment
• Hosts added with a comment only match lines with the same comment
• Comments are never modified on existing lines
• If no matching line exists, a new line is created

CLI Usage

# Add host with a comment
sudo txeh add 127.0.0.1 myapp --comment "local development"
# Result: 127.0.0.1        myapp # local development

# Add another host with the same comment (groups together)
sudo txeh add 127.0.0.1 myapp2 --comment "local development"
# Result: 127.0.0.1        myapp myapp2 # local development

# Add host with a different comment (new line)
sudo txeh add 127.0.0.1 api --comment "staging environment"
# Result: 127.0.0.1        api # staging environment

# Add host without a comment (only matches lines without comments)
sudo txeh add 127.0.0.1 test
# Result: goes to first 127.0.0.1 line that has NO comment, or creates new line

Library Usage

// Add hosts with a comment
hosts.AddHostWithComment("127.0.0.1", "myapp", "local development")
hosts.AddHostsWithComment("127.0.0.1", []string{"svc1", "svc2"}, "my project services")

// Add hosts without a comment (original behavior)
hosts.AddHost("127.0.0.1", "myhost")
hosts.AddHosts("127.0.0.1", []string{"a", "b", "c"})

Example Scenario

Starting hosts file:

127.0.0.1        localhost
127.0.0.1        app1 app2 # dev services

Listing and Removing by Comment

List all hosts with a specific comment:

sudo txeh list bycomment "dev services"

Remove all entries with a specific comment (removes entire lines):

sudo txeh remove bycomment "dev services"

Modifying Comments

Comments are never modified on existing lines. To change a comment, remove the hosts first and re-add them with the new comment:

# Remove all entries with the old comment
sudo txeh remove bycomment "old comment"

# Re-add with the new comment
sudo txeh add 127.0.0.1 app1 app2 --comment "new comment"

txeh Go Library

Dependency:

go get github.com/txn2/txeh

Example Golang Implementation:

package main

import (
    "fmt"

    "github.com/txn2/txeh"
)

func main() {
    // Load the system hosts file
    hosts, err := txeh.NewHostsDefault()
    if err != nil {
        panic(err)
    }

    // Add hosts (without comments)
    hosts.AddHost("127.100.100.100", "myapp")
    hosts.AddHost("127.100.100.101", "database")
    hosts.AddHosts("127.100.100.102", []string{"cache", "queue", "search"})

    // Add hosts with comments (for tracking/organization)
    hosts.AddHostWithComment("127.100.100.200", "api.local", "development services")
    hosts.AddHostsWithComment("127.100.100.201", []string{"web.local", "admin.local"}, "frontend apps")

    // Query existing entries
    addresses := hosts.ListAddressesByHost("myapp", true)
    fmt.Printf("myapp resolves to: %v\n", addresses)

    hostnames := hosts.ListHostsByIP("127.100.100.102")
    fmt.Printf("Hosts at 127.100.100.102: %v\n", hostnames)

    // List all hosts with a specific comment
    devHosts := hosts.ListHostsByComment("development services")
    fmt.Printf("Dev service hosts: %v\n", devHosts)

    // Remove entries
    hosts.RemoveHost("database")
    hosts.RemoveHosts([]string{"cache", "queue"})
    hosts.RemoveAddress("127.1.27.1")
    hosts.RemoveAddresses([]string{"127.1.27.15", "127.1.27.14"})

    // Remove all entries with specific comments
    hosts.RemoveByComment("frontend apps")
    hosts.RemoveByComments([]string{"old environment", "deprecated"})

    // RemoveCIDRs returns an error (CIDR parsing can fail)
    if err := hosts.RemoveCIDRs([]string{"10.0.0.0/8"}); err != nil {
        panic(err)
    }

    // Preview changes
    fmt.Println(hosts.RenderHostsFile())

    // Save changes
    err = hosts.Save()
    if err != nil {
        panic(err)
    }
    // Or save to a specific file: hosts.SaveAs("./custom.hosts")
}

Build Release

Build test release:

goreleaser --skip-publish --clean --skip-validate

Build and release:

GITHUB_TOKEN=$GITHUB_TOKEN goreleaser --clean

License

Apache License 2.0