gv2gml:tldr:67165

This command performs a series of actions using several commands:

1. cat ${input-gv}: The cat command is used to concatenate files and display their contents. In this case, it is used with ${input-gv} which is a variable expansion. It means that the value of the input-gv variable (if it exists) will be used as the input file for cat. So, the command reads the contents of the file specified by the input-gv variable.

2. |: The pipe symbol (|) is a command-line operator that allows the output of one command to be used as the input for another command. In this case, the output of the cat command is piped (or transferred) as input to the next command.

3. gv2gml: This is a command that takes input in GraphViz format (gv) and converts it to the Graph Modeling Language (gml) format. The piped input from the previous command (cat) is received by gv2gml, which performs the conversion.

4. > ${output-gml}: The > symbol is used for output redirection. It means that the output of the previous command, gv2gml, will be saved to the file specified by the output-gml variable. This variable is expanded to its value, and > redirects the output to that file.

Overall, this command takes the contents of a file specified by ${input-gv}, converts it from GraphViz format to Graph Modeling Language format using gv2gml, and saves the converted output to a file specified by ${output-gml}.