Bash hostname completion | Arabesque

Bash hostname completion | Arabesque

As part of its programmable completion suite, Bash includes hostname completion. This completion mode reads hostnames from a file in hosts(5) format to find possible completions matching the current word. On Unix-like operating systems, it defaults to reading the file in its usual path at /etc/hosts.

For example, given the following hosts(5) file in place at /etc/hosts:

127.0.0.1      localhost  192.0.2.1      web.example.com www  198.51.100.10  mail.example.com mx  203.0.113.52   radius.example.com rad  

An appropriate call to compgen would yield this output:

$ compgen -A hostname  localhost  web.example.com  www  mail.example.com  mx  radius.example.com  rad  

We could then use this to complete hostnames for network diagnostic tools like ping(8):

$ complete -A hostname ping  

Typing ping we and then pressing Tab would then complete to ping web.example.com. If the shopt option hostcomplete is on, which it is by default, Bash will also attempt host completion if completing any word with an @ character in it. This can be useful for email address completion or for SSH username@hostname completion.

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