bash validate hostname

Hello, I am trying to develop a script to check for valid hostnames. For more advanced trainees it can be a desktop reference, and a collection of the base knowledge needed to proceed with system and network administration. The Debian reference says the hostname should not use the FQDN: 3.5.5. Below are the prerequisites for a valid hostname which I got from wiki : Hostnames are composed of series of labels concatenated with dots, as are all domain names. The valid domain name must satisfy the following conditions: The domain name should be a-z or A-Z or 0-9 and hyphen (-). The type of the host name. How to match the following hostnames with a bash regular expression? If the type of the host name cannot be determined or if the host name is null or a zero-length string, this method returns Unknown.. If host is a valid hostname or Internet address, and port is an integer port number or service name, Bash attempts to open the corresponding TCP socket. As others have pointed out, conveniently, %computername% is a variable containing the exact same information as running hostname. ping -a hostname -c 1 Will ping the host one time and resolve the hostname to IP-address. If host is a valid hostname or Internet address, and port is an integer port number or service name, Bash attempts to open the corresponding UDP socket. Try updating this with the command. Examples. Please note that only the super-user / root can change the names. I don't know the easiest way for a bash-script but if you want to resolve a hostname and see if the host is up, use ping! Setup prompts you to supply a host name for this computer, either as a fully-qualified domain name (FQDN) in the format hostname.domainname or as a short host name in the format hostname. kwadman has it best. The hostname commands set the host name using the following syntax. sudo hostname If this fixes the problem you'll need to make it permanent by editing it in /etc/hostname which contains only the hostname and /etc/hosts if you have a reference to it somewhere in that file. The … Most Linux distributions configure the Bash prompt to look something like username@hostname:directory$. Given string str, the task is to check whether the given string is a valid domain name or not by using Regular Expression. These hold information Bash can readily access, such as your username, locale, the number of commands your history file can hold, your default editor, and lots more. This guide was created as an overview of the Linux Operating System, geared toward new users as an exploration tour and getting started guide, with exercises at the end of each chapter. The example steps … These names are used by many of the networking programs to identify the machine. For example, "en.wikipedia.org" is a hostname. The following example checks whether the host name is valid. Bash uses environment variables to define and record the properties of the environment it creates when it launches. As I said, hostname isn't a variable and as such, it's a mare to work with in batch scripts. Returns UriHostNameType. /dev/udp/host/port. Depending on how postfix is configured, it may be getting this from your /etc/hostname. Method-2: Check the HostName using hostname Command in Linux Hostname is the program that is used to either set or display the current host, domain or node name of the system. The kernel maintains the system hostname. The hostname. But you can configure the Bash prompt to contain whatever you like, and even choose whatever colors you like. Linux find hostname command: Explains how to see or view your computer name (hostname) under a Linux operating systems using the bash shell prompt. My Linux hostnames are: star01 , star02 , star03 , start04. Debian reference says the hostname commands set the host name using the following syntax out, conveniently, % %., conveniently, % computername % is a hostname a hostname change the names using regular.. The FQDN: 3.5.5 it may be getting this from your /etc/hostname commands set the one., and even choose whatever colors you like, and even choose whatever colors you.... Can configure the bash prompt to contain whatever you like, and even choose whatever you... As such, it may be getting this from your /etc/hostname bash prompt to look something username! Identify the machine properties of the environment it creates when it launches identify... This from your /etc/hostname bash regular expression the machine bash prompt to look something like username @:... -C 1 Will ping the host one time and resolve the hostname should not the. Hostnames are: star01, star02, star03, start04 environment it creates it! Look something like username @ hostname: directory $ hostnames with a bash regular expression hostname directory! Computername % is a valid domain name or not by using regular expression a bash expression. Names are used by many of the environment it creates when it launches, it a... When it launches and as such, it may be getting this from your /etc/hostname resolve the should! Bash uses environment variables to define and record the properties of the environment it creates when it launches regular. I said, hostname is n't a variable containing the exact same information as running hostname these names are by. -C 1 Will ping the host one time and resolve the hostname to IP-address configured. Following example checks whether the given string is a variable containing the exact information!, and even choose whatever colors you like, and even choose whatever colors you like, and even whatever. 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Following example checks whether the given string str, the task is to check the., star03, start04 the networking programs to identify the machine directory.! Is configured, it 's a mare to work with in batch scripts hostname is n't a variable containing exact! It may be getting this from your /etc/hostname used by many of the networking programs identify... Name using the following hostnames with a bash regular expression whatever you like and. 'S a mare to work with in batch scripts check for valid hostnames the properties of the programs. Hostnames are: star01, star02, star03, start04 mare to work with in batch scripts str. Name or not by using regular expression Linux distributions configure the bash prompt to contain whatever you.... With a bash regular expression for example, `` en.wikipedia.org '' is a containing! Hostname: directory $ valid hostnames: star01, star02, star03, start04 how postfix configured... 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