Lum – How to use column to delimit on tabs and not spaces

columnscommand linequotingtext processing

I'd like to use the Unix column command to format some text. I have fields delimited by tabs, but within each field there are also spaces. column delimits on white space (tabs and spaces). How can I make column only use tabs as the delimiter?

I was trying to specify tab as the delimiter using:

cat myfile | column -t -s"\t"

Best Answer

column -t -s '\t'

would separate columns on \ and t characters.

column -s \t is the same as column -s t, as the backslash is interpreted as a quoting operator by the shell.

Here you want to pass a real TAB character to column. With ksh93, zsh, bash, mksh, busybox sh or FreeBSD sh:

column -ts $'\t'

Or enter a real tab character by typing Ctrl-V Tab at the shell prompt (within quotes or preceded by a backslash as the tab character is a token separator in the shell syntax just like space), or use "$(printf '\t')" (those double quotes needed to disable the split+glob operator as the tab character also happens to be in the default value of $IFS).

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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).

Lum – Select certain column of each file, paste to a new file

with paste under bash you can do:

paste <(cut -f 4 1.txt) <(cut -f 4 2.txt) .... <(cut -f 4 20.txt)

With a python script and any number of files (python scriptname.py column_nr file1 file2 ... filen):

#! /usr/bin/env python

# invoke with column nr to extract as first parameter followed by
# filenames. The files should all have the same number of rows

import sys

col = int(sys.argv[1])
res = {}

for file_name in sys.argv[2:]:
    for line_nr, line in enumerate(open(file_name)):
        res.setdefault(line_nr, []).append(line.strip().split('\t')[col-1])

for line_nr in sorted(res):
    print '\t'.join(res[line_nr])

Best Answer

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Shell – How to expand tabs based on content

Lum – Select certain column of each file, paste to a new file

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