Involved Source Files Package tabwriter implements a write filter (tabwriter.Writer) that
translates tabbed columns in input into properly aligned text.
The package is using the Elastic Tabstops algorithm described at
http://nickgravgaard.com/elastictabstops/index.html.
The text/tabwriter package is frozen and is not accepting new features.
Code Examples
package main
import (
"fmt"
"os"
"text/tabwriter"
)
func main() {
w := new(tabwriter.Writer)
// Format in tab-separated columns with a tab stop of 8.
w.Init(os.Stdout, 0, 8, 0, '\t', 0)
fmt.Fprintln(w, "a\tb\tc\td\t.")
fmt.Fprintln(w, "123\t12345\t1234567\t123456789\t.")
fmt.Fprintln(w)
w.Flush()
// Format right-aligned in space-separated columns of minimal width 5
// and at least one blank of padding (so wider column entries do not
// touch each other).
w.Init(os.Stdout, 5, 0, 1, ' ', tabwriter.AlignRight)
fmt.Fprintln(w, "a\tb\tc\td\t.")
fmt.Fprintln(w, "123\t12345\t1234567\t123456789\t.")
fmt.Fprintln(w)
w.Flush()
}
package main
import (
"fmt"
"os"
"text/tabwriter"
)
func main() {
// Observe how the b's and the d's, despite appearing in the
// second cell of each line, belong to different columns.
w := tabwriter.NewWriter(os.Stdout, 0, 0, 1, '.', tabwriter.AlignRight|tabwriter.Debug)
fmt.Fprintln(w, "a\tb\tc")
fmt.Fprintln(w, "aa\tbb\tcc")
fmt.Fprintln(w, "aaa\t") // trailing tab
fmt.Fprintln(w, "aaaa\tdddd\teeee")
w.Flush()
}
package main
import (
"fmt"
"os"
"text/tabwriter"
)
func main() {
// Observe that the third line has no trailing tab,
// so its final cell is not part of an aligned column.
const padding = 3
w := tabwriter.NewWriter(os.Stdout, 0, 0, padding, '-', tabwriter.AlignRight|tabwriter.Debug)
fmt.Fprintln(w, "a\tb\taligned\t")
fmt.Fprintln(w, "aa\tbb\taligned\t")
fmt.Fprintln(w, "aaa\tbbb\tunaligned") // no trailing tab
fmt.Fprintln(w, "aaaa\tbbbb\taligned\t")
w.Flush()
}
Package-Level Type Names (only one)
/* sort by: | */
A Writer is a filter that inserts padding around tab-delimited
columns in its input to align them in the output.
The Writer treats incoming bytes as UTF-8-encoded text consisting
of cells terminated by horizontal ('\t') or vertical ('\v') tabs,
and newline ('\n') or formfeed ('\f') characters; both newline and
formfeed act as line breaks.
Tab-terminated cells in contiguous lines constitute a column. The
Writer inserts padding as needed to make all cells in a column have
the same width, effectively aligning the columns. It assumes that
all characters have the same width, except for tabs for which a
tabwidth must be specified. Column cells must be tab-terminated, not
tab-separated: non-tab terminated trailing text at the end of a line
forms a cell but that cell is not part of an aligned column.
For instance, in this example (where | stands for a horizontal tab):
aaaa|bbb|d
aa |b |dd
a |
aa |cccc|eee
the b and c are in distinct columns (the b column is not contiguous
all the way). The d and e are not in a column at all (there's no
terminating tab, nor would the column be contiguous).
The Writer assumes that all Unicode code points have the same width;
this may not be true in some fonts or if the string contains combining
characters.
If [DiscardEmptyColumns] is set, empty columns that are terminated
entirely by vertical (or "soft") tabs are discarded. Columns
terminated by horizontal (or "hard") tabs are not affected by
this flag.
If a Writer is configured to filter HTML, HTML tags and entities
are passed through. The widths of tags and entities are
assumed to be zero (tags) and one (entities) for formatting purposes.
A segment of text may be escaped by bracketing it with [Escape]
characters. The tabwriter passes escaped text segments through
unchanged. In particular, it does not interpret any tabs or line
breaks within the segment. If the [StripEscape] flag is set, the
Escape characters are stripped from the output; otherwise they
are passed through as well. For the purpose of formatting, the
width of the escaped text is always computed excluding the Escape
characters.
The formfeed character acts like a newline but it also terminates
all columns in the current line (effectively calling [Writer.Flush]). Tab-
terminated cells in the next line start new columns. Unless found
inside an HTML tag or inside an escaped text segment, formfeed
characters appear as newlines in the output.
The Writer must buffer input internally, because proper spacing
of one line may depend on the cells in future lines. Clients must
call Flush when done calling [Writer.Write]. Flush should be called after the last call to [Writer.Write] to ensure
that any data buffered in the [Writer] is written to output. Any
incomplete escape sequence at the end is considered
complete for formatting purposes. A [Writer] must be initialized with a call to Init. The first parameter (output)
specifies the filter output. The remaining parameters control the formatting:
minwidth minimal cell width including any padding
tabwidth width of tab characters (equivalent number of spaces)
padding padding added to a cell before computing its width
padchar ASCII char used for padding
if padchar == '\t', the Writer will assume that the
width of a '\t' in the formatted output is tabwidth,
and cells are left-aligned independent of align_left
(for correct-looking results, tabwidth must correspond
to the tab width in the viewer displaying the result)
flags formatting control Write writes buf to the writer b.
The only errors returned are ones encountered
while writing to the underlying output stream.
*Writer : internal/bisect.Writer
*Writer : io.Writer
func NewWriter(output io.Writer, minwidth, tabwidth, padding int, padchar byte, flags uint) *Writer
func (*Writer).Init(output io.Writer, minwidth, tabwidth, padding int, padchar byte, flags uint) *Writer
Package-Level Functions (only one)
NewWriter allocates and initializes a new [Writer].
The parameters are the same as for the Init function.
Package-Level Constants (total 7)
Force right-alignment of cell content.
Default is left-alignment.
Print a vertical bar ('|') between columns (after formatting).
Discarded columns appear as zero-width columns ("||").
Handle empty columns as if they were not present in
the input in the first place.
To escape a text segment, bracket it with Escape characters.
For instance, the tab in this string "Ignore this tab: \xff\t\xff"
does not terminate a cell and constitutes a single character of
width one for formatting purposes.
The value 0xff was chosen because it cannot appear in a valid UTF-8 sequence.
Ignore html tags and treat entities (starting with '&'
and ending in ';') as single characters (width = 1).
Strip Escape characters bracketing escaped text segments
instead of passing them through unchanged with the text.
Always use tabs for indentation columns (i.e., padding of
leading empty cells on the left) independent of padchar.
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