sed:tldr:c733c

This command is running a shell command and piping its output to the sed command. Let's break it down:

${command}: This is a placeholder that represents the command whose output we want to process with sed. It could be any valid shell command.

|: The pipe symbol | in Unix or Linux shell is used to redirect the output of one command as the input to another command. In this case, we are redirecting the output of ${command} to the sed command.

sed: sed stands for "stream editor" and is a powerful Unix utility for text processing and manipulation. It reads text input line by line, applies specified operations, and produces the modified output.

-n: This option tells sed to suppress automatic printing of input lines. Without this option, sed would print every line of the input stream.

'1p': This is a sed command that specifies an operation to be performed on the input. In this case, 1p tells sed to print the first line of the input.

So, when ${command} runs and produces output, it is piped to sed, which only prints the first line of that output.