NAME

App::CSVUtils::csv_select_fields - Select (only output) field(s) using a combination of excludes/includes, including by regex

VERSION

This document describes version 1.033 of App::CSVUtils::csv_select_fields (from Perl distribution App-CSVUtils), released on 2023-09-06.

FUNCTIONS

csv_select_fields

Usage:

csv_select_fields(%args) -> [$status_code, $reason, $payload, \%result_meta]

Select (only output) field(s) using a combination of excludes/includes, including by regex.

Examples:

Select a single field from CSV:

csv_select_fields(input_filename => "file.csv", include_fields => ["f1"]);

Select several fields from CSV:

csv_select_fields(input_filename => "file.csv", include_fields => ["f1", "f2", "f3"]);

Select fields matching regex from CSV:

csv_select_fields(input_filename => "file.csv", include_field_pat => "/^extra_/");

Select all fields except specified from CSV:

csv_select_fields(
    input_filename    => "file.csv",
  include_field_pat => ".*",
  include_fields    => ["f1", "f2"]
);

Only show what fields would be included, then exit:

csv_select_fields(
    input_filename       => "file.csv",
  include_field_pat    => "/^extra_/",
  show_selected_fields => 1
);

(No description)

This function is not exported.

Arguments ('*' denotes required arguments):

exclude_field_pat => re

Field regex pattern to exclude, takes precedence over --field-pat.
exclude_fields => array[str]

Field names to exclude, takes precedence over --fields.
ignore_unknown_fields => bool

When unknown fields are specified in --include-field (--field) or --exclude-field options, ignore them instead of throwing an error.
include_field_pat => re

Field regex pattern to select, overidden by --exclude-field-pat.
include_fields => array[str]

Field names to include, takes precedence over --exclude-field-pat.
inplace => true

Output to the same file as input.

Normally, you output to a different file than input. If you try to output to the same file (-o INPUT.csv -O) you will clobber the input file; thus the utility prevents you from doing it. However, with this --inplace option, you can output to the same file. Like perl's -i option, this will first output to a temporary file in the same directory as the input file then rename to the final file at the end. You cannot specify output file (-o) when using this option, but you can specify backup extension with -b option.

Some caveats:
- if input file is a symbolic link, it will be replaced with a regular file;
- renaming (implemented using rename()) can fail if input filename is too long;
- value specified in -b is currently not checked for acceptable characters;
- things can also fail if permissions are restrictive;
inplace_backup_ext => str (default: "")

Extension to add for backup of input file.

In inplace mode (--inplace), if this option is set to a non-empty string, will rename the input file using this extension as a backup. The old existing backup will be overwritten, if any.
input_escape_char => str

Specify character to escape value in field in input CSV, will be passed to Text::CSV_XS.

Defaults to \\ (backslash). Overrides --input-tsv option.
input_filename => filename (default: "-")

Input CSV file.

Use - to read from stdin.

Encoding of input file is assumed to be UTF-8.
input_header => bool (default: 1)

Specify whether input CSV has a header row.

By default, the first row of the input CSV will be assumed to contain field names (and the second row contains the first data row). When you declare that input CSV does not have header row (--no-input-header), the first row of the CSV is assumed to contain the first data row. Fields will be named field1, field2, and so on.
input_quote_char => str

Specify field quote character in input CSV, will be passed to Text::CSV_XS.

Defaults to " (double quote). Overrides --input-tsv option.
input_sep_char => str

Specify field separator character in input CSV, will be passed to Text::CSV_XS.

Defaults to , (comma). Overrides --input-tsv option.
input_tsv => true

Inform that input file is in TSV (tab-separated) format instead of CSV.

Overriden by --input-sep-char, --input-quote-char, --input-escape-char options. If one of those options is specified, then --input-tsv will be ignored.
output_always_quote => bool (default: 0)

Whether to always quote values.

When set to false (the default), values are quoted only when necessary:
```
field1,field2,"field three contains comma (,)",field4
```
When set to true, then all values will be quoted:
```
"field1","field2","field three contains comma (,)","field4"
```
output_escape_char => str

Specify character to escape value in field in output CSV, will be passed to Text::CSV_XS.

This is like --input-escape-char option but for output instead of input.

Defaults to \\ (backslash). Overrides --output-tsv option.
output_filename => filename

Output filename.

Use - to output to stdout (the default if you don't specify this option).

Encoding of output file is assumed to be UTF-8.
output_header => bool

Whether output CSV should have a header row.

By default, a header row will be output if input CSV has header row. Under --output-header, a header row will be output even if input CSV does not have header row (value will be something like "col0,col1,..."). Under --no-output-header, header row will not be printed even if input CSV has header row. So this option can be used to unconditionally add or remove header row.
output_quote_char => str

Specify field quote character in output CSV, will be passed to Text::CSV_XS.

This is like --input-quote-char option but for output instead of input.

Defaults to " (double quote). Overrides --output-tsv option.
output_quote_empty => bool (default: 0)

Whether to quote empty values.

When set to false (the default), empty values are not quoted:
```
field1,field2,,field4
```
When set to true, then empty values will be quoted:
```
field1,field2,"",field4
```
output_sep_char => str

Specify field separator character in output CSV, will be passed to Text::CSV_XS.

This is like --input-sep-char option but for output instead of input.

Defaults to , (comma). Overrides --output-tsv option.
output_tsv => bool

Inform that output file is TSV (tab-separated) format instead of CSV.

This is like --input-tsv option but for output instead of input.

Overriden by --output-sep-char, --output-quote-char, --output-escape-char options. If one of those options is specified, then --output-tsv will be ignored.
overwrite => bool

Whether to override existing output file.
show_selected_fields => true

Show selected fields and then immediately exit.

Returns an enveloped result (an array).

First element ($status_code) is an integer containing HTTP-like status code (200 means OK, 4xx caller error, 5xx function error). Second element ($reason) is a string containing error message, or something like "OK" if status is 200. Third element ($payload) is the actual result, but usually not present when enveloped result is an error response ($status_code is not 2xx). Fourth element (%result_meta) is called result metadata and is optional, a hash that contains extra information, much like how HTTP response headers provide additional metadata.

Return value: (any)

HOMEPAGE

Please visit the project's homepage at https://metacpan.org/release/App-CSVUtils.

SOURCE

Source repository is at https://github.com/perlancar/perl-App-CSVUtils.

AUTHOR

perlancar <perlancar@cpan.org>

CONTRIBUTING

To contribute, you can send patches by email/via RT, or send pull requests on GitHub.

Most of the time, you don't need to build the distribution yourself. You can simply modify the code, then test via:

% prove -l

If you want to build the distribution (e.g. to try to install it locally on your system), you can install Dist::Zilla, Dist::Zilla::PluginBundle::Author::PERLANCAR, Pod::Weaver::PluginBundle::Author::PERLANCAR, and sometimes one or two other Dist::Zilla- and/or Pod::Weaver plugins. Any additional steps required beyond that are considered a bug and can be reported to me.

COPYRIGHT AND LICENSE

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

BUGS

Please report any bugs or feature requests on the bugtracker website https://rt.cpan.org/Public/Dist/Display.html?Name=App-CSVUtils

When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature.

To install App::CSVUtils, copy and paste the appropriate command in to your terminal.

cpanm

cpanm App::CSVUtils

CPAN shell

perl -MCPAN -e shell
install App::CSVUtils

For more information on module installation, please visit the detailed CPAN module installation guide.

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