Dateien und stdin lesen

A useful CLI usually reads something: a file you name, or text piped into it. Zig gives you clear, explicit ways to do both. 📥

Use std.fs.cwd to get the current directory, then openFile to open a path relative to it for reading.

An open file is a resource you own. Pair the open with a defer file.close() so it is released no matter how the function exits.

To slurp everything at once, call readToEndAlloc with an allocator and a size limit. It returns the bytes as an owned slice.

That returned slice lives on the heap, so you own it. Add defer a.free(data) to release the buffer when you are done with it.

That max-bytes argument protects you from a huge file eating all memory. Pick a limit that fits your tool's realistic input.

To read piped text, reach for std.io.getStdIn. It hands back a file just like one you opened, so the same reading calls apply.

Ask stdin for a reader and call readAllAlloc. This collects everything piped in until end-of-input into one owned slice.

For streaming work, a reader's readUntilDelimiterOrEof pulls one line at a time into a buffer, returning null when input ends.

Each raw read can be a system call. Wrap a reader in std.io.bufferedReader so many small reads batch into fewer, faster operations.

Because a file and stdin both expose a reader, your parsing logic does not care which one it got. That is clean, reusable design. ✨

Recall how you turn a file's bytes into something you can use.

You opened files with openFile, read them fully or line by line, pulled text from stdin, and freed every buffer. Input handled. 🎯