unix command to extract part of a hostname

Question

I would like to extract the first part of this hostname testsrv1 from testsrv1.main.corp.loc.domain.com in UNIX, within a shell script.

What command can I use? It would be anything before the first period .

Answer 1

Do you have the server name in a shell variable? Are you using a sh-like shell? If so,

${SERVERNAME%%.*}

will do what you want.

Answer 2

You can use cut:

echo "testsrv1.main.corp.loc.domain.com" | cut -d"." -f1

Answer 3

To build upon pilcrow's answer, no need for new variable, just use inbuilt $HOSTANME.

echo $HOSTNAME-->my.server.domain
echo ${HOSTNAME%%.*}-->my

Tested on two fairly different Linux's.

2.6.18-371.4.1.el5, GNU bash, version 3.2.25(1)-release (i386-redhat-linux-gnu) 3.4.76-65.111.amzn1.x86_64, GNU bash, version 4.1.2(1)-release (x86_64-redhat-linux-gnu)

Answer 4

try the -s switch: hostname -s

Answer 5

I use command cut, awk, sed or bash variables

Operation

Via cut

[flying@lempstacker ~]$ echo "testsrv1.main.corp.loc.domain.com" | cut -d. -f1
testsrv1
[flying@lempstacker ~]$

Via awk

[flying@lempstacker ~]$ echo "testsrv1.main.corp.loc.domain.com" | awk -v FS='.' '{print $1}'
testsrv1
[flying@lempstacker ~]$

Via sed

[flying@lempstacker ~]$ echo "testsrv1.main.corp.loc.domain.com" | sed -r 's@([^.]*).(.*)@\1@g'
testsrv1
[flying@lempstacker ~]$

Via Bash Variables

[flying@lempstacker ~]$ hostName='testsrv1.main.corp.loc.domain.com'
[flying@lempstacker ~]$ echo ${hostName%%.*}
testsrv1
[flying@lempstacker ~]$

Answer 6

You could have used "uname -n" to just get the hostname only.

Answer 7

You can use IFS to split text by whichever token you want. For domain names, we can use the dot/period character.

#!/usr/bin/env sh

shorthost() {
  # Set IFS to dot, so that we can split $@ on dots instead of spaces.
  local IFS='.'

  # Break up arguments passed to shorthost so that each domain zone is
  # a new index in an array.
  zones=($@)

  # Echo out our first zone
  echo ${zones[0]}
}

If this is in your script then, for instance, you'll get test when you run shorthost test.example.com. You can adjust this to fit your use case, but knowing how to break the zones into the array is the big thing here, I think.

I wanted to provide this solution, because I feel like spawning another process is overkill when you can do it easily and completely within your shell with IFS. One thing to watch out for is that some users will recommend doing things like hostname -s, but that doesn't work in the BSD userland. For instance, MacOS users don't have the -s flag, I don't think.

Answer 8

Assuming the variable $HOSTNAME exists, so try echo ${HOSTNAME%%.*} to get the top-most part of the full-qualified hostname. Hope it helps.

If interested, the hint is from the below quoted partial /etc/bashrc on a REHL7 host:

      if [ -e /etc/sysconfig/bash-prompt-screen ]; then
          PROMPT_COMMAND=/etc/sysconfig/bash-prompt-screen
      else
          PROMPT_COMMAND='printf "\033k%s@%s:%s\033\\" "${USER}" "${HOSTNAME%%.*}" "${PWD/#$HOME/~}"'
      fi
      ;; ... ```