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fcmp/README.md

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# fcmp - compare file identity
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A small shell util that compares files for identity with `mmap()` and `memcmp()`.
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# Usage
`fcmp` produces no output, but success is indicated by its return code.
```shell
$ fcmp file1 file2 && echo "Equal!"
```
You can pass any number of files, but at least 2 must be provided.
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| Code | Meaning |
|------|--------------------------------------------------------------|
| 0 | The files are equal |
| 1 | The files are unequal |
| 2 | The files have unequal lengths, and therefor must be unequal |
| -1 | There was an error |
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You can use this in shell scripts easily:
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``` shell
# Example
if fcmp "$1" "$2"; then
echo "Files are equal!"
else
echo "Files are not equal!"
fi
```
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# Building
To build normally, run `make`.
## Release target
Build with default optimisations using `make release`, it will output a stripped binary at `fcmp-release`.
### Notes
* The Makefile uses variables `RELEASE_CFLAGS` and `RELEASE_LDFLAGS` to apply optimisations (and `DEBUG_CFLAGS` + `DEBUG_LDFLAGS` for extra compiler flags with the debug target). If needed you can set these yourself to prevent the defaults.
* The default `OPT_FLAGS` specify `-march=native` which may be undesireable for you. Set the variable or modify the Makefile if you need to remove this.
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## PGO
Building with Profile Guided Optimisation is supported with the `pgo` Makefile target. It uses the same rules as the `release` target and outputs a binary to `fcmp-pgo`.
There may be small performance improvements from using this target instead of `release`, but the difference is mostly negligable.
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## Debug target
Build with debugging information and no optimisations using `make debug`, it will output a binary at `fcmp-debug`.
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## Notes
- Before switching between targets, make sure to run `make clean`.
- GCC + Graphite compiler specific optimisation flags are added by default with the `OPT_FLAGS` variable. Override this variable if using another compiler that doesn't support these optimisations.
### Multithreading
- By default, parallel processing is enabled when building through `libpthread`, to build a single-threaded version override the variables `FEAT_CFLAGS` and `FEAT_LDFLAGS` to empty.
- By default the program will decide at runtime whether or not to use parallelised processing. You can set `FEAT_CFLAGS="-D_RUN_THREADED=1"` to _force_ the use of a parallelised run every time in the binary, although this is not recommended.
- Performance gains from parallelised runs mostly appear with a large number of files being compared at once, as the task delegation overhead is surpassed.
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# License
GPL'd with <3