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select.rs
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select.rs
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use csv;
use CliResult;
use config::{Config, Delimiter};
use select::SelectColumns;
use util;
static USAGE: &'static str = "
Select columns from CSV data efficiently.
This command lets you manipulate the columns in CSV data. You can re-order
them, duplicate them or drop them. Columns can be referenced by index or by
name if there is a header row (duplicate column names can be disambiguated with
more indexing). Finally, column ranges can be specified.
Select the first and fourth columns:
$ xsv select 1,4
Select the first 4 columns (by index and by name):
$ xsv select 1-4
$ xsv select Header1-Header4
Ignore the first 2 columns (by range and by omission):
$ xsv select 3-
$ xsv select '!1-2'
Select the third column named 'Foo':
$ xsv select 'Foo[2]'
Re-order and duplicate columns arbitrarily:
$ xsv select 3-1,Header3-Header1,Header1,Foo[2],Header1
Quote column names that conflict with selector syntax:
$ xsv select '\"Date - Opening\",\"Date - Actual Closing\"'
Usage:
xsv select [options] [--] <selection> [<input>]
xsv select --help
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. (i.e., They are not searched, analyzed,
sliced, etc.)
-d, --delimiter <arg> The field delimiter for reading CSV data.
Must be a single character. (default: ,)
";
#[derive(Deserialize)]
struct Args {
arg_input: Option<String>,
arg_selection: SelectColumns,
flag_output: Option<String>,
flag_no_headers: bool,
flag_delimiter: Option<Delimiter>,
}
pub fn run(argv: &[&str]) -> CliResult<()> {
let args: Args = util::get_args(USAGE, argv)?;
let rconfig = Config::new(&args.arg_input)
.delimiter(args.flag_delimiter)
.no_headers(args.flag_no_headers)
.select(args.arg_selection);
let mut rdr = rconfig.reader()?;
let mut wtr = Config::new(&args.flag_output).writer()?;
let headers = rdr.byte_headers()?.clone();
let sel = rconfig.selection(&headers)?;
if !rconfig.no_headers {
wtr.write_record(sel.iter().map(|&i| &headers[i]))?;
}
let mut record = csv::ByteRecord::new();
while rdr.read_byte_record(&mut record)? {
wtr.write_record(sel.iter().map(|&i| &record[i]))?;
}
wtr.flush()?;
Ok(())
}