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24 lines
725 B
Markdown
24 lines
725 B
Markdown
## An implementation of the unix "cat" program
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In this program each command-line argument is assumed to be a filename, the file
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is opened, and printed to stdout.
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```ts
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for (let i = 0; i < Deno.args.length; i++) {
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const filename = Deno.args[i];
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const file = await Deno.open(filename);
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await Deno.copy(file, Deno.stdout);
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file.close();
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}
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```
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The `copy()` function here actually makes no more than the necessary kernel ->
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userspace -> kernel copies. That is, the same memory from which data is read
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from the file, is written to stdout. This illustrates a general design goal for
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I/O streams in Deno.
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Try the program:
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```shell
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deno run --allow-read https://deno.land/std@$STD_VERSION/examples/cat.ts /etc/passwd
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```
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