Shell – Print table with empty columns for consecutive delimiters

columnsshelltext formatting

I typically use column to convert input into a table, eg:

$ echo 'a\tb\tc\nd\te\tf' | column -t -s $'\t'
a  b  c
d  e  f

However it collapses empty columns eg:

$ echo 'a\tb\tc\nd\t\tf' | column -t -s $'\t'
a  b  c
d  f

Rather than printing an empty column when there are consecutive delimiters. This is what I would like, using column or otherwise:

a  b  c
d     f

Best Answer

If you use GNU column:

-n
By default, the column command will merge multiple adjacent delimiters into a single delimiter when using the -t option; this option disables that behavior. This option is a Debian GNU/Linux extension.

printf 'a\tb\tc\nd\t\tf\n'  | column -t -n -s $'\t'

Output:

a  b  c
d     f

If GNU column is not available, you can use sed to add a space (or something else, e.g. a -) between the tabs:

printf 'a\tb\tc\nd\t\tf\n'  | sed -e ':loop; s/\t\t/\t-\t/; t loop' | column -t -s $'\t'

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Shell – How to expand tabs based on content

If you have column(1), an old BSD tool, try column -t, for pretty-printing tables.

To ensure empty cells are displayed, you could try the approach of inserting a single space in each empty cell (recognizable by two consecutive tabs). The idea is column(1) should give the space character its own column but being a single character in width it should not affect the table dimensions or be visible in the output to humans.

generate_tsv | 
   awk '/\t\t/ { for (i = 0; i < 2; i++) gsub(/\t\t/, "\t \t") } 1' | 
   column -t -s $'\t'

The extra awk inserted in the pipeline does the inserting of spaces into each empty cell, as described. 2 passes are necessary to handle 2 consecutive empty cells (\t\t\t).

How to Use cut to Separate by Multiple Whitespace

If we use tr command along with squeeze option (-s flag ) to convert all multiple consecutive spaces to a single space and then perform cut operation with space as delimiter – we can access the required column carrying the numbers.

Refer to the code snipped bellow:

cat file | tr -s ' ' | cut -d ' ' -f 8

Best Answer

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How to Use cut to Separate by Multiple Whitespace

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