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README.md

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+# SortBin: a tool for sorting binary records
+
+SortBin is a tool for sorting arrays of binary data records.
+It is similar to the Unix `sort` utility.
+But where `sort` works with lines of text, SortBin works with fixed-length binary data records.
+
+SortBin reads input from a file, sorts it, and writes the sorted data to an output file.
+These files contain flat, raw arrays of fixed-length binary data records.
+
+Records are interpreted as fixed-length strings of 8-bit unsigned integers.
+These records are sorted in lexicographic order.
+This means that records are sorted by their first byte, then records with equal first bytes are sorted by their second bytes, and so on.
+
+SortBin can sort very large data files which do not fit in memory.
+In such cases, a temporary file is used to store intermediate results.
+The program starts by separately sorting blocks of data that do fit in memory.
+It then iteratively merges these blocks into larger sorted blocks until the complete file is sorted.
+
+This program is designed to work with relatively short data records, up to about 20 bytes.
+Sorting larger records should work, but may be inefficient.
+
+## Usage
+
+SortBin has only been tested on Linux.
+
+To use SortBin, you must compile the source code.
+Clone the repository, then build as follows:
+```
+git clone https://github.com/jorisvr/...
+cd sortbin
+make
+```
+
+You can now sort data like this:
+```
+build/sortbin --size=10 --memory=2G input.dat output.dat
+```
+
+* _size_ specifies the record size in bytes
+* _memory_ specifies the amount of RAM that SortBin may use
+