From 34ec3b225425cecdccf754fbc87f4a8f3728890d Mon Sep 17 00:00:00 2001 From: Luca Casonato Date: Thu, 7 May 2020 00:21:13 +0200 Subject: Multi page manual (#5110) --- docs/examples/unix_cat.md | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) create mode 100644 docs/examples/unix_cat.md (limited to 'docs/examples/unix_cat.md') diff --git a/docs/examples/unix_cat.md b/docs/examples/unix_cat.md new file mode 100644 index 000000000..7534ef0d0 --- /dev/null +++ b/docs/examples/unix_cat.md @@ -0,0 +1,24 @@ +## An implementation of the unix "cat" program + +In this program each command-line argument is assumed to be a filename, the file +is opened, and printed to stdout. + +```ts +for (let i = 0; i < Deno.args.length; i++) { + let filename = Deno.args[i]; + let file = await Deno.open(filename); + await Deno.copy(file, Deno.stdout); + file.close(); +} +``` + +The `copy()` function here actually makes no more than the necessary kernel -> +userspace -> kernel copies. That is, the same memory from which data is read +from the file, is written to stdout. This illustrates a general design goal for +I/O streams in Deno. + +Try the program: + +```shell +$ deno run --allow-read https://deno.land/std/examples/cat.ts /etc/passwd +``` -- cgit v1.2.3