# xan slice ```txt Returns rows of a CSV file in the specified range. This range can be specified through 0-based rows indices, byte offsets in the file and using custom expressions as start & stop conditions. Slicing the 10 first rows of a file: $ xan slice -l 10 file.csv Slicing rows between indices 5 and 10: $ xan slice -s 5 -e 10 file.csv Retrieving rows at some indices: $ xan slice -I 4,5,19,65 file.csv Retrieving last 5 rows: $ xan slice -L 5 file.csv Slicing rows starting at some byte offset in the file: $ xan slice -B 56356 file.csv Slicing rows until a row where the "count" column is over `45`: $ xan slice -E 'count > 45' file.csv The command will of course terminate as soon as the specified range of rows is found and won't need to read to whole file or stream if unnecessary. Of course, flags related to byte offsets will only work with seekable inputs, e.g. files on disk but no stdin nor gzipped files. Note that it is perfectly fine to mix & match flags related to row indices, byte offsets and conditions. In which case, here is description of the order of operations: - First, the command will seek in target file if -B/--byte-offset was given, and won't read past a certain byte offset if --end-byte was given. - Then the -S/--start-condition and -E/--end-condtion apply. - Finally flags related to row indices will apply. Note that indices are therefore relative to both the application of the byte offset and the start condition and not to the first actual row in the file. So, for instance, if you want to slice 5 rows in the file but only after a row where the "count" column is over `10`, you could do the following: $ xan slice -S 'count > 10' -l 5 file.csv Usage: xan slice [options] [] slice options to use with row indices: -s, --start The index of the row to slice from. --skip Same as -s, --start. -e, --end The index of the row to slice to. -l, --len The length of the slice (can be used instead of --end). -i, --index Slice a single row (shortcut for -s N -l 1). -I, --indices Return a slice containing multiple indices at once. You must provide the indices separated by commas, e.g. "1,4,67,89". Note that selected rows will be emitted in file order, not in the order given. -L, --last Return last rows from file. Incompatible with other flags. Runs in O(n) time & memory if file is seekable. Else runs in O(N) time (N being the total number of rows of the file) and O(n) memory. slice options to use with expressions: -S, --start-condition Do not start yielding rows until given expression returns true. -E, --end-condition Stop yielding rows as soon as given expression returns false. slice options to use with byte offets: -B, --byte-offset Byte offset to seek to in the sliced file. This can be useful to access a particular slice of rows in constant time, without needing to read preceding bytes. You must provide a byte offset starting a CSV row or the output could be corrupted. This requires the input to be seekable (stdin or gzipped files not supported). --end-byte Only read up to provided position in byte, exclusive. This requires the input to be seekable (stdin or gzipped files not supported). --raw Raw slicing that forego parsing CSV data for better performance. Only use if you know what you are doing. Common options: -h, --help Display this message -o, --output Write output to instead of stdout. -n, --no-headers When set, the first row will not be interpreted as headers. Otherwise, the first row will always appear in the output as the header row. -d, --delimiter The field delimiter for reading CSV data. Must be a single character. ```