The return values of hostname -f and uname -n may be different

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At work , Due to the operation requirements of the software used , I met Linux Most systems will set the host name to something like test.laowang.cn Such a fully qualified domain name . In contact with Linux At the beginning of the , I learned through the Internet , The command to get the fully qualified domain name is hostname -f , And when writing scripts , Use this command frequently . And then , I took over what other colleagues wrote shell Script , Read uname -n This order . This command is the first time I have seen , After checking its general function on the Internet , Then run this command on the computer , The fully qualified domain name is also found . then , I thought hostname -f And uname -n The return value of , It's the same , All are Linux The fully qualified domain name of the system .

The return value is the same

In general , If in /etc/hostname and /etc/hosts The same host name is written in , that hostname -f And uname -n The return value of is the same , As shown in the figure below ：

When the return value is different

Only later , The return values of these two commands are likely to be different . If you will /etc/hostname The value in is set to a single word that is not separated by a dot . meanwhile , stay /etc/hosts in , For this machine ip Set two machine names , And only the shorter one is related to /etc/hostname Consistent values for , You can make hostname -f And uname -n The return value of is different . As shown in the figure below ：

Compare hostname and uname command

By looking at the help of the two commands , I can see hostname It is mainly used to view or set the host name -f The parameter indicates the fully qualified domain name ,-s Parameter represents short name . and uname The full English name of the command is “Unix name”, Used to display system related information , For example, host name 、 Kernel version number 、 Hardware architecture, etc ,-n Indicates the name of the output local network node .

Current operations show that ,hostname -f And uname -n The return value of may be different ,hostname -s And uname -n The return value of is generally the same . But I can't tell hostname -s And uname -n It's two equivalent commands , So when we program , It's best not to be in a program , Alternate the two commands to get the hostname .

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