ttyplot:tldr:991e2

This command is a pipeline that makes use of multiple commands and a utility called "ttyplot" to visualize data on a terminal screen.

Here is an explanation of each part:

1. { echo ${1 2 3}; cat }: This is a compound command that consists of two parts separated by a semicolon.

   • echo ${1 2 3}: This command prints the values of the positional parameters (variables that hold arguments passed to a script or function) $1, $2, and $3. For example, if you execute the script with the command bash script.sh value1 value2 value3, this part will output "value1 value2 value3" to stdout.

   • cat: This command is used to read and display the contents of files. In this case, it will read from stdin (standard input) and display it.

   The compound command effectively outputs the values passed as arguments ($1, $2, and $3) followed by any input from stdin.

2. |: This is the pipe operator, which connects the output of the previous command to the input of the next command.

3. ttyplot -t ${title} -u ${unit}: This is the command ttyplot with options specified.

   • ttyplot: It is a utility that creates a scrolling graph on a terminal. The graph is updated in real-time as new data is received.

   • -t ${title}: This option specifies the title of the graph. ${title} is a variable holding the value of the shell variable title, which should be defined before executing the command.

   • -u ${unit}: This option specifies the unit of measurement for the graph. ${unit} is a variable holding the value of the shell variable unit, which should be defined before executing the command.

In summary, this command takes three arguments as input and then pipes that input, together with any input coming from stdin, to ttyplot which creates a scrolling graph on the terminal screen. The graph will have a title and a unit of measurement specified by the variables title and unit respectively.