ucw-tableprinter - a program module for customizable printing of tables.


The table printer module is a part of the LibUCW library. It provides formatting of 2-dimensional tables in various ways. Users seldom interact with the table printer itself, but programs using it often provide means for customizing table output by passing options.

This manual page describes the overall logic of the table printer and its options.

Each table print-out consists of a number of rows, which are processed one after another. All rows have the same number of columns. Once a table is defined, it can be printed using a variety of formatters (block-line, human-readable, machine-readable, etc.).

The table definition consists of various column definitions, each column definition is a pair consisting of a name and a type. Name of each column must be unique in the whole table. Each column definition can be instantiated (printed) in its own format, e.g., a size column can be printed three times: first in bytes, then in gigabytes, and finally in a human-readable form.

The table can be controlled using various options:

option argument meaning


0 or 1

set whether a table header should be printed



equivalent to header:0


comma-separated column list

set order of columns and per-column options (see below)



set table formatter to one of the built-in formatters (see below)



set column delimiter



set column cell format mode, possibilities are: default, raw, pretty



set column cell format to raw data, equivalent to cells:raw



set column cell format to pretty-printing, equivalent to cells:pretty

Table formats

The fmt option sets the overall format of the table. Currently, the following formats are available:

  • human-readable (human): prints columns separated by a single space, rows separated by a newline character (ASCII 0x0a).

  • machine-readable (machine): prints columns separated by a tab character (ASCII 0x09), rows separated by a newline character.

  • block-line (block): prints each column on one line, rows separated by a single blank line. That is, the column separator is set to the newline character and an extra newline is printed at the end of each row.

Column definitions

The cols option allows to specify a list of table columns and their options. For instance, you can use name,size[raw],size[pretty] to request a table with three columns: name, size as a raw value, and the same size pretty-printed.

Formally, the argument of the cols option follows this grammar:

<col-order-string> := <col-def>[,<col-def>]*
<col-def> := <col-name> [ '[' <col-opts> ']' ]
<col-name> contains no commas nor square brackets
<col-opts> := <col-opt> [ ',' <col-opt> ]
<col-opt> contains no commas nor square brackets

Column options

All column types accept these standard formatting modes:

  • default: human-readable, but not hostile to machine parsing

  • raw: raw data with no frills

  • pretty: tries to please humans (e.g., like ls -h)

There are also formatting modes specific for particular column types:

  • Sizes can be given a unit (KB, MB, GB, TB, or auto; case-insensitive).

  • Timestamps can be formatted as timestamp or epoch (both are seconds since the Unix epoch), or datetime (corresponds to date(1) format "%F %T". Currently, raw is an alias for timestamp and pretty is the same as datetime.