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70 lines
3.9 KiB
70 lines
3.9 KiB
# `sink` - sinks all input into `/dev/null`
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Small and fast util that re-routes `stdin`, `stdout` (and optionally, `stderr`) of a program to `/dev/null` without needing to spawn a (sub-)shell.
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Can be useful in some situations (*see example below*.)
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## Usage
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Command usage is in the form of: `./sink [<program name> [<arguments...>]]`.
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Example:
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```shell
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$ sink cat sink.c # Identical to `>>/dev/null 0>&1 cat sink.c`, but will not cause cat to error on `stdin` being a redirect to an output stream.
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```
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When invoked with `<program name>`: `execve()`s into the program (if it exists or is found in `$PATH`) with `<arguments....>` and a passed-through `envp` (see below in *Compiler flags* on changing this behaviour.)
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## Building
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Run `make && sudo make install` to build with full optimisations and install `sink` to `/usr/local/bin/sink`. (run `sudo make uninstall` to remove.)
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To build for debugging, run `make debug`.
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### Feature flags
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Set the following to the environment variable `FEATURES` when invoking `make` to build with the speficied features' behaviour (e.g. `FEATURES=NO_SEARCH_PATH\ NO_ENV make`.)
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When a debug-mode splash screen is printed, the features the binary was compiled with are also printed.
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* `REPLACE_STDERR` - Re-route the child program's `stderr` stream to the sink as well. By default, it is passed through as default.
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* `NO_SEARCH_PATH` - Prevent the program looking up its argument in the `PATH` environment variable.
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* `NO_ENV` - Prevent `envp` passthrough to the `execve()`'d program.
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* `DEBUG_IGNORE_SPLASH` - Do not print project and version info in debug builds on startup.
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### Installation
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The program must have been built before installation, and installation and uninstallation must be done as root.
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By default, `make install` will install `sink` to `$(DESTDIR)$(PREFIX)/bin`. You can override this by setting `PREFIX=/path/to/usr make install`
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To install a different target, for example, `debug`, run `make debug && sudo make install OUTPUT=sink-debug` (`OUTPUT` is the binary name.)
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*NOTE*: You must specify the same `OUTPUT` value for `make uninstall` if done this way.
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### Target CPU
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If building on a VPS, you may want to run `TARGET_ARCH= make` instead of `make`, to build for generic CPU instead of the default native target for optimised (`release`) builds.
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### Static linkage
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By default, the program is entirely statically linked. To override this, run `SHARED=yes make`, for any building target.
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### Stripping
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To build optimised without stripping the symbol table, run `make release` or `make STRIP=:`.
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For installing *without* stripping the symbol table, run `sudo make install STRIP=true`; the effect is the same as `STRIP=:` which does not work for the `install` target.
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### Other targets
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* `sink` (**default**): stripped `release` target. output: `sink`
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* `release`: optimised build. output: `sink-release`
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* `debug`: unoptimised build with debuginfo. output: `sink-debug`
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* `clean`: remove all previous object and binary output files
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### Environment variables
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* `PREFIX` - The installation path prefix. Defaults to `/usr/local` if not set.
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* `SHARED` - set to "yes" to prevent passing `--static` to cc
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* `TARGET_ARCH` - target arch (`-march=`), or set `TARGET_ARCH=` to force set to generic target. (default [release only]: `native`)
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* `CFLAGS`, `COMMON_FLAGS` - passthrough to cc
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* `LDFLAGS` - passthrough to ld
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* `DEBUG_CFLAGS`, `DEBUG_LDFLAGS` - passthrough to cc / ld on target `debug`
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* `RELEASE_CFLAGS`, `RELEASE_LDFLAGS` - passthrough to cc / ld on target `release`
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#### Make overridable only
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* `STRIP` - Strip command for default output (stripped release) target (`make sink`). set `make STRIP=:` to prevent stripping entirely. (NOTE: When using `make install`, `STRIP=:` will not work, instead, paradoxically, set `STRIP=true`, they have the same effect for all targets)
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* `OUTPUT` - The name of the output binary from the default target, and the binary that `install`/`uninstall` targets look for.
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# License
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GPL'd with <3
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