Align cout format as table's columns

Question

I'm pretty sure this is a simple question in regards to formatting but here's what I want to accomplish:

I want to output data onto the screen using cout. I want to output this in the form of a table format. What I mean by this is the columns and rows should be properly aligned. Example:

Test                 1
Test2                2
Iamlongverylongblah  2
Etc                  1

I am only concerned with the individual line so my line to output now (not working) is

cout << var1 << "\t\t" << var2 << endl;

Which gives me something like:

Test                 1
Test2                  2
Iamlongverylongblah         2
Etc                  1

Mouse

Answer 1

setw.

#include <iostream>
#include <iomanip>
using namespace std;

int main () {
  cout << setw(21) << left << "Test"    << 1 << endl;
  cout << setw(21) << left << "Test2"   << 2 << endl;
  cout << setw(21) << left << "Iamlongverylongblah"     << 2 << endl;
  cout << setw(21) << left << "Etc"     << 1 << endl;
  return 0;
}

Clere

You forgot to add "<< left". This is required if you want left-aligned fixed fields. – Pinta

std::left is not reset on every formatted output, you only need it once. (The stream's width is reset.) – Sandbank

Answer 2

I advise using Boost Format. Use something like this:

cout << format("%|1$30| %2%") % var1 % var2;

Vala

Answer 3

You must find the length of the longest string in the first column. Then you need to output each string in the first column in a field with the length being that of that longest string. This necessarily means you can't write anything until you've read each and every string.

Planetoid

Isn't there a easier way? Using setw or something. – Mouse

>Isn't there a easier way? Not unless you can predict the future. >Using setw or something. Yes, setw is one way to "output each string in the first column in a field with the length being that of that longest string." – Buehler

Most formatted output I've seen doesn't bother to find the max size of a field and if it overruns a decent value, oh well, but the formatting looks a little weird when it does. – Lorinalorinda

Answer 4

You might want to use std::format

with alignment syntax "{:<30} | {:<30}\n". This enables you to format your text using an aligment with a specific width.

To format a table you would append to a std:string table_rows and format the elements with alignment and width, like so:

table_rows += format("{:<32} | {:<30}\n", str_col_1, str_col_2);

For debugging some fill-in chars might come handy, which you can set like this: format("{:*<32} | {:+<30}\n" ... .

In case you really need to work with dynamic width, then determine the longest "str_col_1" and use it as another parameter to format:

std::format("{:<{}}", "left aligned", 30);

Example:

#include <iostream>
#include <string>
#include <fmt/format.h>

int main()
{
    std::string table_rows;
    std::string str_col_1[] = {"Name", "Age", "Gender", "City"};
    std::string str_col_2[] = {"John", "25", "Male", "New York"};

    for (int i = 0; i < 4; i++) {
        table_rows += fmt::format("{:<10} | {:<15}\n", str_col_1[i], str_col_2[i]);
    }

    std::cout << table_rows << "\n";

    return 0;
}

Output:

Name       | John           
Age        | 25             
Gender     | Male           
City       | New York 

Referencing:

https://en.cppreference.com/w/cpp/utility/format/formatter https://fmt.dev/latest/syntax.html

Nathalienathan

Answer 5

you can do it with

string str = "somthing";
printf ("%10s",str);
printf ("%10s\n",str);
printf ("%10s",str);
printf ("%10s\n",str);

Trihydric

Surely he already knows that with "printf" it can be done. He is specifically asking for "cout". – Cassicassia

How do you know what he (OP) knows? OP never said he tried printf, nor that he wants just cout based answer (-(-1)). – Agreeable

cout is in the title and they wrote: "I want to output data onto the screen using cout" – Berley