I work with CSV files and sometimes need to quickly check the contents of a row or column from the command line. In many cases cut, head, tail, and friends will do the job; however, cut cannot easily deal with situations such as

"this, is the first entry", this is the second, 34.5

Here, the first comma is part of the first field, but cut -d, -f1 disagrees. Before I write a solution myself, I was wondering if anyone knew of a good tool that already exists for this job. It would have to, at the very least, be able to handle the example above and return a column from a CSV formatted file. Other desirable features include the ability to select columns based on the column names given in the first row, support for other quoting styles and support for tab-separated files.

If you don't know of such a tool but have suggestions regarding implementing such a program in Bash, Perl, or Python, or other common scripting languages, I wouldn't mind such suggestions.

17 Answers 17

up vote 34 down vote accepted

You can use Python's csv module.

A simple example:

import csv
reader = csv.reader(open("test.csv", "rb"))
for row in reader:
    for col in row:
        print col
  • 2
    Even better, use Pandas. It is explicitly designed to work with tabular data. – Josh Jul 15 '14 at 19:24
  • 2
    there is no reason beside regular expression to use perl anyway, and regex are not the answer this time – pqnet Aug 12 '14 at 5:58
  • 1
    @pqnet "there is no reason beside regular expression to use perl anyway" -- troll much? – jrw32982 Jun 22 '15 at 16:38
  • 3
    @jrw32982 No trolling, I honestly believe there is some truth in the sentence "he had a problem, he decided to solve it with perl, now he has two problems". I would suggest against perl except if your problem is based on regular language parsing, and that's almost never the case. – pqnet Jun 23 '15 at 15:41
  • 2
    @pqnet so you mean: "for me there is no reason to use perl other than regexp" - that's a reasonable statement. For the rest of the world, your original statement was just a troll. – jrw32982 Jun 23 '15 at 19:39

I am probably a little bit too late, but there is another tool worth mentioning: csvkit

http://csvkit.readthedocs.org/

It has a lot of command line tools that can:

  • convert to and from csv from various formats (json, sql, xls)
  • cut, grep, sort and others
  • join different csv files!
  • 5
    An excellent tool that meets the question criteria wonderfully (in particular it doesn't require jumping into a programming language and is well crafted to fit with other Unix utilities). – mm2001 Nov 4 '14 at 20:10

Sounds like a job for Perl with Text::CSV.

perl -MText::CSV -pe '
    BEGIN {$csv = Text::CSV->new();}
    $csv->parse($_) or die;
    @fields = $csv->fields();
    print @fields[1,3];
'

See the documentation for how to handle column names. The separator and quoting style can be tuned with parameters to new. See also Text::CSV::Separator for separator guessing.

  • Is there a one liner you can compact this into. I like perl, but only when I can invoke it directly from the command line rather than with a script – user7000 Jan 26 '17 at 6:04
  • 1
    @user7000, unless your shell is (t)csh that command would work just fine at the prompt of your shell. You can always joins those lines together if you want it on one line. newline is generally just like space in the perl syntax like in C. – Stéphane Chazelas Sep 12 '17 at 12:07
  • I guess. Though squashing more than 2 lines into 1 isn't what I really mean by a one liner. I was hoping there was some syntactic sugar that would do some of it implicitly (like how the -e creates an implicit loop). – user7000 Sep 12 '17 at 22:33

I've found csvfix, a command line tool does the job well. You will need to make it yourself however:

http://neilb.bitbucket.org/csvfix

It does all the things you'd expect, order/select columns, split/merge and many you wouldn't like generating SQL inserts from CSV data and diffing CSV data.

R is not my favorite programming language, but it is good for things like this. If your csv file is

***********
foo.csv
***********
 col1, col2, col3
"this, is the first entry", this is the second, 34.5
'some more', "messed up", stuff

Inside the R interpreter type

> x=read.csv("foo.csv", header=FALSE)

> x
                     col1                col2   col3
1 this, is the first entry  this is the second   34.5
2              'some more'           messed up  stuff
> x[1]  # first col
                      col1
1 this, is the first entry
2              'some more'
> x[1,] # first row
                      col1                col2  col3
1 this, is the first entry  this is the second  34.5

With regard to your other requests, for "the ability to select columns based on the column names given in the first row" see

> x["col1"]
                      col1
1 this, is the first entry
2              'some more'

For "support for other quoting styles" see the quote argument to read.csv (and related functions). For "support for tab-separated files" see the sep argument to read.csv (set sep to '\t').

For more information see the online help.

> help(read.csv)
  • I'm very familiar with R, but my goal was to have something I could use easily from Bash. – Steven D Apr 6 '11 at 15:03
  • 1
    @Steven: R can easily be run from the command line, in the same way as Python or Perl, if that is your only concern. See Rscript (part of the base R distribution) or the addon package littler. You can do #!/usr/bin/env Rscript or similar. – Faheem Mitha Apr 7 '11 at 18:21
  • Ah yes. I'm pretty proficient in R but hadn't used it much to create this type of utility. I have something working in Python but I may try to create something in R as well. – Steven D Apr 10 '11 at 1:05

I used csvtool once and it saved me a lot of time and trouble. Callable from the shell.

http://caml.inria.fr/cgi-bin/hump.en.cgi?contrib=447

If you want to use the command-line (and do not create an entire program to do the job), you'd like to use rows, a project I'm working on: it's a command-line interface to tabular data but also a Python library to use in your programs. With the command-line interface you can pretty-print any data in CSV, XLS, XLSX, HTML or any other tabular format supported by the library with a simple command:

rows print myfile.csv

If myfile.csv is like this:

state,city,inhabitants,area
RJ,Angra dos Reis,169511,825.09
RJ,Aperibé,10213,94.64
RJ,Araruama,112008,638.02
RJ,Areal,11423,110.92
RJ,Armação dos Búzios,27560,70.28

Then rows will print the contents in a beautiful way, like this:

+-------+-------------------------------+-------------+---------+
| state |              city             | inhabitants |   area  |
+-------+-------------------------------+-------------+---------+
|    RJ |                Angra dos Reis |      169511 |  825.09 |
|    RJ |                       Aperibé |       10213 |   94.64 |
|    RJ |                      Araruama |      112008 |  638.02 |
|    RJ |                         Areal |       11423 |  110.92 |
|    RJ |            Armação dos Búzios |       27560 |   70.28 |
+-------+-------------------------------+-------------+---------+

Installing

If you are a Python developer and already have pip installed on your machine, just run inside a virtualenv or with sudo:

pip install rows

If you're using Debian:

sudo apt-get install rows

Other Cool Features

Converting Formats

You can convert between any supported format:

rows convert myfile.xlsx myfile.csv

Querying

Yes, you can use SQL into a CSV file:

$ rows query 'SELECT city, area FROM table1 WHERE inhabitants > 100000' myfile.csv
+----------------+--------+
|      city      |  area  |
+----------------+--------+
| Angra dos Reis | 825.09 |
|       Araruama | 638.02 |
+----------------+--------+

Converting the output of the query to a file instead of stdout is also possible using the --output parameter.

As a Python Library

You can you in your Python programs too:

import rows
table = rows.import_from_csv('myfile.csv')
rows.export_to_txt(table, 'myfile.txt')
# `myfile.txt` will have same content as `rows print` output

Hope you enjoy it!

Or, you could try some awk magic. Howewer, I'm not a good awk user and cannot confirm this would work properly, and how to do it.

To use python from the command line, you can check out pythonpy (https://github.com/Russell91/pythonpy):

$ echo $'a,b,c\nd,e,f' | py '[x[1] for x in csv.reader(sys.stdin)']
b
e

try "csvtool" this package it's handy command line tool for handling CSV files

  • 1
    Already mentioned, with more detail... – jasonwryan Sep 3 '15 at 9:27

cissy will also do command-line csv processing. It's written in C (small/lightweight) with rpm and deb packages available for most distros.

Using the example:

echo '"this, is the first entry", this is the second, 34.5' | cissy -c 1
"this, is the first entry"

or

echo '"this, is the first entry", this is the second, 34.5' | cissy -c 2
 this is the second

or

echo '"this, is the first entry", this is the second, 34.5' | cissy -c 2-
 this is the second, 34.5

Miller is another nice tool for manipulating name-based data, including CSV (with headers). To extract the first column of a CSV file, without caring about its name, you’d do something like

printf '"first,column",second,third\n1,2,3\n' |
  mlr --csv --implicit-csv-header --headerless-csv-output cut -f 1
  • Miller is very impressive. I'd compare it to awk, but highly DSV-aware. – Derek Mahar Apr 18 at 21:59

There is also a Curry library for reading/writing files in CSV format: CSV.

  • 2
    Would you mind posting some sample code, like the Perl, Python and R answers? (Especially since Curry is not a common unix scripting language.) – Gilles Apr 20 '11 at 21:31
  • @Gilles: Yes, you are right, I should post some sample code to make the answer better. I'm going to do this in a while. – imz -- Ivan Zakharyaschev Apr 20 '11 at 21:36

The github repo Structured Text Tools has a useful list of relevant linux command line tools. In particular, the Delimiter Separated Values section lists several CSV capable tools that directly support the operations requested.

An awk solution

awk -vq='"' '
func csv2del(n) {
  for(i=n; i<=c; i++)
    {if(i%2 == 1) gsub(/,/, OFS, a[i])
    else a[i] = (q a[i] q)
    out = (out) ? out a[i] : a[i]}
  return out}
{c=split($0, a, q); out=X;
  if(a[1]) $0=csv2del(1)
  else $0=csv2del(2)}1' OFS='|' file

I'd recommend xsv - A fast CSV command line toolkit written in Rust (Github).

Written by Ripgrep's author.

Featured in How we made our CSV processing 142x faster (Reddit thread).

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