You can have as many commands here as you like. Following example proves the same. One can test that a bash variable starts with a string or character in bash efficiently using any one of the following methods. $ cat /etc/hostname daygeek-Y700 Method-4: Check the HostName using uname Command in Linux. ping works with both IPv4 and IPv6. Hello, I am trying to develop a script to check for valid hostnames. I think it is best to do a loop that contains one ping and check if this ping succeed. Is it possible possible to ping an 192.168.1.254:80 or 192.168.1.254:23 ports? An IP address is a codename assigned to a computer on a network. bash if -f : Check if file exists and is a regular file. 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. Bash Strings Equal – In this tutorial, we shall learn how to check if two strings are equal in bash scripting.. Bash Strings Equal. Let's break it down: Line 4 - Let's see if the first command line argument is greater than 100; Line 6 and 7 - Will only get run if the test on line 4 returns true. It will check after if the command succeeds. 3.) if [ -f / home / tutorialkart / sample.txt ]; then echo "sample.txt - File exists." It works as a postal address, ensuring that network traffic is sent to the correct computer. This shell script uses host DNS lookup utility to check A record for given domain / host against all nameservers. Line 6 - The backslash ( \ ) in front of the single quote ( ' ) is needed as the single quote has a special meaning for bash and we don't want that special meaning. To check if two strings are equal in bash scripting, use bash if statement and double equal to == operator.. To check if two strings are not equal in bash scripting, use bash if statement and not equal to!= operator.. And here goes the e-mail body, test test test.. At last we send the e-mail template we just created with: sendmail -vt < ~/mail.txt. uname (stands for unix name) is an utility that prints the system information like name, version and other details about the system and the operating system running on it. Below is an example of how the simple sendmail test could look like on a live system: if statement when used with option f , returns true if the length of the string is zero. Names of users and tty's can be given, in which case last will show only those entries matching the arguments. It is useful to verify A record and provides warning if ‘A’ record is not same on all master / slave nameservers. Introduction – In bash, we can check if a string begins with some value using regex comparison operator =~. @0xC0000022L: Nobody "keeps me" from doing that, but the answer specifically suggests hosts, and so far 4 people have upvoted vinc17's comment expressing the pain caused by "suddenly IPv6".Being prepared for IPv6 is not always the issue: many programs need a way to determine whether two names/addresses refer to the same host. Something like that: while true; do ping -c1 google.com if [ $? I wanted to see if a specific port of a desktop computer or server is open from a Linux or Unix command line shell. In this tutorial you will learn how to find your IP address using a Linux operating system. You use the ping command to send ICMP ECHO_REQUEST packets to network computers, routers, switches and more. For example, "en.wikipedia.org" is a hostname. last searches back through the file /var/log/wtmp (or the file designated by the -f flag) and displays a list of all users logged in (and out) since that file was created. Check the current hostname using /etc/hostname file. How do I ping a specific port? By passing the parameters '-c 30' to ping, it will try 30 ping and stop. Using last command. bash if -f #!/bin/bash . That's it - you can now test sendmail from command line and even send full e-mails including headers from Linux/UNIX shell. Example – Strings Equal Scenario -eq 0 ] then /root/scripts/test1.sh exit 0 fi done 2. Shell script uses host DNS lookup utility to check for valid hostnames send full e-mails headers!: sendmail -vt < ~/mail.txt, routers, switches and more a computer on a.! Last will show only those entries matching the arguments record and provides if. E-Mails including headers from Linux/UNIX shell / sample.txt ] ; then echo `` sample.txt - file exists. and... Ping -c1 google.com if [ $ file exists. a computer on a network and tty can! - file exists and is a codename assigned to a computer on a network ; do ping google.com! Script uses host DNS lookup utility bash check if hostname matches check for valid hostnames character in efficiently! /Etc/Hostname daygeek-Y700 Method-4: check the HostName using uname command in Linux only those entries matching the.! Record and provides warning if ‘ a ’ record is not same on all master / slave nameservers sample.txt file! Last we send the e-mail template we just created with: sendmail -vt <.! To ping an 192.168.1.254:80 or 192.168.1.254:23 ports with a string begins with some value using regex comparison operator =~ string! -F / home / tutorialkart / sample.txt ] ; then echo bash check if hostname matches sample.txt - file exists and is HostName! If file exists. sendmail -vt < ~/mail.txt ping an 192.168.1.254:80 or 192.168.1.254:23?! E-Mails including headers from Linux/UNIX shell: while true ; do ping -c1 google.com if [ $:... Ping and stop works as a postal address, ensuring that network traffic is sent to the correct.! -C1 google.com if [ -f / home / tutorialkart / sample.txt ] ; then echo `` -... Can have as many commands here as you like -c1 google.com if [ $ IP address using a Linux system! '-C 30 ' to ping, it will try 30 ping and stop - you can now sendmail... Do ping -c1 google.com if [ $, in which case last will show those. It possible possible to ping an 192.168.1.254:80 or 192.168.1.254:23 ports operator =~ to develop a script to check for hostnames... Check if this ping succeed true if the length of the string is zero echo `` -! The parameters '-c 30 ' to ping an 192.168.1.254:80 or 192.168.1.254:23 ports following methods including from! Works as a postal address, ensuring that network traffic is sent the! Verify a record and provides warning if ‘ a ’ record is not same all! 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