Single and double horizontal lines in Linux commands are called command line options
Single horizontal line
The parameter following the single horizontal line option must be a single-character parameter . One character represents one parameter, and multiple parameters can be written after the same horizontal line.
tar -xcvf ×××
When the option needs to add parameters, the parameters can be immediately after the option or separated by spaces.
mysql -u root -p
mysql -uroot -p
Double horizontal line
The parameter following the double line option must be a multi-character parameter (word), and the double line can only be followed by one parameter.
tar --help
When the options need to add parameters, the parameters can be separated by "=" or separated by spaces.
git branch --set-upstream-to origin/remote_branch your_branch
git branch --set-upstream-to=origin/remote_branch your_branch