Add auto complete to your ssh, put into your .bash_profile

Mac SSH Autocomplete

_complete_ssh_hosts ()
{
        COMPREPLY=()
        cur="${COMP_WORDS[COMP_CWORD]}"
        comp_ssh_hosts=`cat ~/.ssh/known_hosts | \
                        cut -f 1 -d ' ' | \
                        sed -e s/,.*//g | \
                        grep -v ^# | \
                        uniq | \
                        grep -v "\[" ;
                cat ~/.ssh/config | \
                        grep "^Host " | \
                        awk '{print $2}'
                `
        COMPREPLY=( $(compgen -W "${comp_ssh_hosts}" -- $cur))
        return 0
}
complete -F _complete_ssh_hosts ssh

Thanks for this script.

I removed the known_hosts section because I want only the .ssh/config file to be parsed.

_complete_ssh_hosts ()
{
        COMPREPLY=()
        cur="${COMP_WORDS[COMP_CWORD]}"
        comp_ssh_hosts=`cat ~/.ssh/config | \
                         grep --color=never "^Host " | \
                         awk '{print $2}'
                   `
        COMPREPLY=( $(compgen -W "${comp_ssh_hosts}" -- $cur))
        return 0
}
complete -F _complete_ssh_hosts ssh

It doesn't work for me, I get ~/.zprofile: command not found: complete

The same. MacOS Monterey 12.5.1

The script is written in bash. zsh has a different way of doing things.

Converted the searches to AWK so there is only 2 commands being called instead of 9 and it is easy to comment out one of the sources if you don't like it.

_complete_ssh_hosts ()
{
        COMPREPLY=()
        cur="${COMP_WORDS[COMP_CWORD]}"
        comp_ssh_hosts=`
            awk '{split($1,aliases,","); if (aliases[1] !~ /^\[/) print aliases[1]}' ~/.ssh/known_hosts ;
            awk '/^Host/ && $2 !~ /[*]/ {print $2}' ~/.ssh/config ;
            `
        COMPREPLY=( $(compgen -W "${comp_ssh_hosts}" -- $cur))
        return 0
}
complete -F _complete_ssh_hosts ssh

Actually, this can work for zsh as well, we just need to enable bash style autocomplete before using this function.
Here is complete example: put this inside ~/.zshrc

#### initialize completion system ####
# see https://unix.stackexchange.com/questions/593433/bash-like-autocompletion-for-ssh-command-in-zsh-shell-with-etc-hosts-file
# see https://zsh.sourceforge.io/Doc/Release/Completion-System.html
autoload -Uz compinit; compinit


# enable bash style autocomplete (requires compinit to be called before this)
# see https://stackoverflow.com/questions/3249432/can-a-bash-tab-completion-script-be-used-in-zsh
# see https://zsh.sourceforge.io/Doc/Release/Completion-System.html
autoload -Uz bashcompinit; bashcompinit


# replace the default ssh autocomplete that comes from compinit 
# with this _complete_ssh_hosts function which looks for hosts in ~/.ssh/config and ~/.ssh/known_hosts
# Note: requires bashcompinit to enable this bash style autocomplete function
# see https://stackoverflow.com/questions/52438964/mac-autocomplete-for-ssh-hosts-in-terminal
# see https://gist.github.com/aliang/1024466
_complete_ssh_hosts ()
{
        COMPREPLY=()
        cur="${COMP_WORDS[COMP_CWORD]}"
        comp_ssh_hosts=`
            awk '{split($1,aliases,","); if (aliases[1] !~ /^\[/) print aliases[1]}' ~/.ssh/known_hosts ;
            awk '/^Host/ && $2 !~ /[*]/ {print $2}' ~/.ssh/config ;
            `
        COMPREPLY=( $(compgen -W "${comp_ssh_hosts}" -- $cur))
        return 0
}
complete -F _complete_ssh_hosts ssh

Thanks!!!

I tweaked it to work when you have multiple known_hosts files, and multiple config files:

# shellcheck shell=bash

# Add tab completion for SSH hostnames
#
# Based on this gist: https://gist.github.com/aliang/1024466
#
# Search in:
#  - ~/.ssh/config
#  - ~/.ssh/config.d/*config
#  - ~/.ssh/*known_hosts

_complete_ssh_hosts ()
{
  COMPREPLY=()
  cur="${COMP_WORDS[COMP_CWORD]}"
  comp_ssh_hosts=$(
    sort -u < <(
      awk '{split($1,aliases,","); if (aliases[1] !~ /^\[/) print aliases[1]}' < <(
        # list all known_hosts files, ignoring blank lines and comments
        # awk code taken from https://stackoverflow.com/a/17396799
        awk '!/^ *#/ && NF' < <(cat ~/.ssh/*known_hosts)
      )
      awk '/^Host/ && $2 !~ /[*]/ {print $2}' <(
        cat ~/.ssh/{config,config.d/*config}
      )
    )
  )
  COMPREPLY=( $(compgen -W "$comp_ssh_hosts" -- $cur) )
  return 0
}
complete -F _complete_ssh_hosts ssh