static USAGE: &str = r#"
Returns the rows in the range specified (starting at 0, half-open interval).
The range does not include headers.
If the start of the range isn't specified, then the slice starts from the first
record in the CSV data.
If the end of the range isn't specified, then the slice continues to the last
record in the CSV data.
This operation can be made much faster by creating an index with 'qsv index'
first. With an index, the command requires parsing just the rows that are
sliced. Without an index, all rows up to the first row in the slice must be
parsed.
Examples:
# Slice from the 3rd record to the end
qsv slice --start 2 data.csv
# Slice the first three records
qsv slice --start 0 --end 2 data.csv
# Slice the first three records (using --len)
qsv slice --len 3 data.csv
# Slice the last record
qsv slice -s -1 data.csv
# Slice the last 10 records
qsv slice -s -10 data.csv
# Get everything except the last 10 records
qsv slice -s -10 --invert data.csv
# Slice the first three records of the last 10 records
qsv slice -s -10 -l 3 data.csv
# Slice the second record
qsv slice --index 1 data.csv
# Slice from the second record, two records
qsv slice -s 1 --len 2 data.csv
# Slice records 10 to 20 as JSON
qsv slice --start 9 --end 19 --json data.csv
# Slice records 1 to 9 and 21 to the end as JSON
qsv slice --start 9 --len 10 --invert --json data.csv
For more examples, see https://github.com/dathere/qsv/blob/master/tests/test_slice.rs.
Usage:
qsv slice [options] [<input>]
qsv slice --help
slice options:
-s, --start <arg> The index of the record to slice from.
If negative, starts from the last record.
-e, --end <arg> The index of the record to slice to.
-l, --len <arg> The length of the slice (can be used instead
of --end).
-i, --index <arg> Slice a single record (shortcut for -s N -l 1).
If negative, starts from the last record.
--json Output the result as JSON. Fields are written
as key-value pairs. The key is the column name.
The value is the field value. The output is a
JSON array. If --no-headers is set, then
the keys are the column indices (zero-based).
--invert slice all records EXCEPT those in the specified range.
Common options:
-h, --help Display this message
-o, --output <file> Write output to <file> 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 <arg> The field delimiter for reading CSV data.
Must be a single character. (default: ,)
"#;
use std::{fs, path::PathBuf};
use serde::Deserialize;
use crate::{
CliResult,
config::{Config, Delimiter},
index::Indexed,
util,
};
#[allow(clippy::unsafe_derive_deserialize)]
#[derive(Deserialize)]
struct Args {
arg_input: Option<String>,
flag_start: Option<isize>,
flag_end: Option<usize>,
flag_len: Option<usize>,
flag_index: Option<isize>,
flag_json: bool,
flag_output: Option<String>,
flag_no_headers: bool,
flag_delimiter: Option<Delimiter>,
flag_invert: bool,
}
pub fn run(argv: &[&str]) -> CliResult<()> {
let mut args: Args = util::get_args(USAGE, argv)?;
let tmpdir = tempfile::tempdir()?;
let work_input = util::process_input(
vec![PathBuf::from(
args.arg_input.clone().unwrap_or_else(|| "-".to_string()),
)],
&tmpdir,
"",
)?;
let input_filename = work_input[0]
.canonicalize()?
.into_os_string()
.into_string()
.unwrap();
args.arg_input = Some(input_filename);
match args.rconfig().indexed()? {
Some(idxed) => args.with_index(idxed),
_ => args.no_index(),
}
}
impl Args {
fn no_index(&self) -> CliResult<()> {
let mut rdr = self.rconfig().reader()?;
let (start, end) = self.range()?;
if self.flag_json {
let headers = rdr.byte_headers()?.clone();
let records = rdr.byte_records().enumerate().filter_map(move |(i, r)| {
let should_include = if self.flag_invert {
i < start || i >= end
} else {
i >= start && i < end
};
if should_include {
Some(r.unwrap())
} else {
None
}
});
util::write_json(
self.flag_output.as_ref(),
self.flag_no_headers,
&headers,
records,
)
} else {
let mut wtr = self.wconfig().writer()?;
self.rconfig().write_headers(&mut rdr, &mut wtr)?;
for (i, r) in rdr.byte_records().enumerate() {
if self.flag_invert == (i < start || i >= end) {
wtr.write_byte_record(&r?)?;
}
}
Ok(wtr.flush()?)
}
}
fn with_index(&self, mut indexed_file: Indexed<fs::File, fs::File>) -> CliResult<()> {
let (start, end) = self.range()?;
if end - start == 0 && !self.flag_invert {
return Ok(());
}
if self.flag_json {
let headers = indexed_file.byte_headers()?.clone();
let total_rows = util::count_rows(&self.rconfig())?;
let records = if self.flag_invert {
let mut records: Vec<csv::ByteRecord> =
Vec::with_capacity(start + (total_rows as usize - end));
indexed_file.seek(0)?;
for r in indexed_file.byte_records().take(start) {
records.push(r.unwrap());
}
indexed_file.seek(end as u64)?;
for r in indexed_file.byte_records().take(total_rows as usize - end) {
records.push(r.unwrap());
}
records
} else {
indexed_file.seek(start as u64)?;
indexed_file
.byte_records()
.take(end - start)
.map(|r| r.unwrap())
.collect::<Vec<_>>()
};
util::write_json(
self.flag_output.as_ref(),
self.flag_no_headers,
&headers,
records.into_iter(),
)
} else {
let mut wtr = self.wconfig().writer()?;
self.rconfig().write_headers(&mut *indexed_file, &mut wtr)?;
let total_rows = util::count_rows(&self.rconfig())? as usize;
if self.flag_invert {
indexed_file.seek(0)?;
for r in indexed_file.byte_records().take(start) {
wtr.write_byte_record(&r?)?;
}
indexed_file.seek(end as u64)?;
for r in indexed_file.byte_records().take(total_rows - end) {
wtr.write_byte_record(&r?)?;
}
} else {
indexed_file.seek(start as u64)?;
for r in indexed_file.byte_records().take(end - start) {
wtr.write_byte_record(&r?)?;
}
}
Ok(wtr.flush()?)
}
}
fn range(&self) -> CliResult<(usize, usize)> {
let mut start = None;
if let Some(start_arg) = self.flag_start {
if start_arg < 0 {
start = Some(
(util::count_rows(&self.rconfig())? as usize)
.abs_diff(start_arg.unsigned_abs()),
);
} else {
start = Some(start_arg as usize);
}
}
let index = if let Some(flag_index) = self.flag_index {
if flag_index < 0 {
let index = (util::count_rows(&self.rconfig())? as usize)
.abs_diff(flag_index.unsigned_abs());
Some(index)
} else {
Some(flag_index as usize)
}
} else {
None
};
Ok(util::range(start, self.flag_end, self.flag_len, index)?)
}
fn rconfig(&self) -> Config {
Config::new(self.arg_input.as_ref())
.delimiter(self.flag_delimiter)
.no_headers_flag(self.flag_no_headers)
}
fn wconfig(&self) -> Config {
Config::new(self.flag_output.as_ref())
}
}