Fsdb::Filter::dbcol(3)

NAME
dbcol - select columns from an Fsdb file

SYNOPSIS
dbcol [-v] [-e -] [column...]

DESCRIPTION
Select one or more columns from the input database. If a value is given for empty columns with the -e option, then any named columns which don't exist will be created. Otherwise, non-existent columns are an error.

Note: a safer way to create columns is dbcolcreate.

OPTIONS

-r or --relaxed-errors
    Relaxed error checking: ignore columns that aren't there.

-v or --invert-match
    Output all columns except those listed (like grep -v).

-e EmptyValue or --empty
    Specify the value newly created columns get.

and the standard fsdb options:

-d  Enable debugging output.

-i or --input InputSource
    Read from InputSource, typically a file, or - for standard input, or (if in Perl) a IO::Handle, Fsdb::IO or Fsdb::BoundedQueue objects.

-o or --output OutputDestination
    Write to OutputDestination, typically a file, or - for standard output, or (if in Perl) a IO::Handle, Fsdb::IO or Fsdb::BoundedQueue objects.

--autorun or --noautorun
    By default, programs process automatically, but Fsdb::Filter objects in Perl do not run until you invoke the run() method. The "--(no)autorun" option controls that behavior within Perl.

--header H
    Use H as the full Fsdb header, rather than reading a header from then input.

--help
    Show help.

--man
    Show full manual.

SAMPLE USAGE

  Input:
    #fsdb account passwd uid gid fullname homedir shell
    johnh * 2274 134 John_Heidemann /home/johnh /bin/bash
    greg * 2275 134 Greg_Johnson /home/greg /bin/bash
    root * 0 0 Root /root /bin/bash
    # this is a simple database

  Command:
    cat DATA/passwd.fsdb account | dbcol account

  Output:
    #fsdb      account
    johnh
    greg
    root
    # this is a simple database
    #  | dbcol account

SEE ALSO
dbcolcreate(1), Fsdb(3)

CLASS FUNCTIONS

  new
    $filter = new Fsdb::Filter::dbcol(@arguments);

Create a new dbcol object, taking command-line arguments.

  set_defaults
    $filter->set_defaults();

Internal: set up defaults.

  parse_options
    $filter->parse_options(@ARGV);

Internal: parse options

  setup
    $filter->setup();

Internal: setup, parse headers.

  run
    $filter->run();

Internal: run over all data rows.

  finish
    $filter->finish();

Internal: write trailer.

AUTHOR and COPYRIGHT
Copyright (C) 1991-2018 by John Heidemann <johnh@isi.edu>

This program is distributed under terms of the GNU general public license, version 2. See the file COPYING with the distribution for details.