An implementation of the unix “cat” program
Concepts
- Use the Deno runtime API to output the contents of a file to the console.
- Deno.args accesses the command line arguments.
- Deno.open is used to get a handle to a file.
- Deno.copy is used to transfer data from the file to the output stream.
- Files should be closed when you are finished with them
- Modules can be run directly from remote URLs.
Example
In this program each command-line argument is assumed to be a filename, the file is opened, and printed to stdout (e.g. the console).
/**
* cat.ts
*/
for (let i = 0; i < Deno.args.length; i++) {
const filename = Deno.args[i];
const file = await Deno.open(filename);
await Deno.copy(file, Deno.stdout);
file.close();
}
To run the program:
deno run --allow-read https://deno.land/std@$STD_VERSION/examples/cat.ts /etc/passwd