Why won't my output align properly in columns? - c++

Question

I have no clue why this wont align properly. I have looked at every other post and topic on aligning basic columns in cout, and I have tried them and it just wont do it.
I need 3 columns to look like so:
1 0 /sbin/init
949 1 /usr/sbin/sshd -D -d
27282 949 sshd: salvucwa [ priv]
27323 27282 sshd: salvucwa#pts/31
27324 27323 -bash
27425 27324 script
27426 27425 bash -i
To do this, I am using this code:
void printData(vector<string> tree) {
for (int i = tree.size()-1; i >= 0; i--) {
string print = tree.at(i);
string pid = print.substr(0, print.find(" "));
print = print.substr(print.find(" "));
string ppid = print.substr(0, print.find(" "));
print = print.substr(print.find(" "));
string cmd = print;
cout << left << setw(5) << pid;
cout << ppid;
cout << setw(50) << cmd << endl;
}
}
The 50 was just a placeholder as I was trying much too large numbers to get it to work, but it hasn't. It aligns the first and second columns just fine, but it ends up printing like this:
1 0 /sbin/init
949 1 /usr/sbin/sshd -D -d
27282 949 sshd: salvucwa [ priv]
27323 27282 sshd: salvucwa#pts/31
27324 27323 -bash
27425 27324 script
27426 27425 bash -i
This first 2 columns are aligned perfectly, but the last one always follows the 2nd column and will not change.
Changing the length of the second setw(5) in the code block also only increases or decreases the space between the first 2 columns, not the last one. Also, changing the last setw() does not seem to have an affect.
Why is this not aligning properly? Sorry, as this is probably a dumb question, but every other post on the same topic I have found does not appear to have a fix and only talks about 2 columns (which my first 2 columns are fine).

Answer 1

Without the full code it's impossible to tell precisely what you're doing wrong, but I'm sure that the code you've provided is not the code that you used to print this.
You are most likely using an insufficient column size to print the numeric data. If your data is 5 characters long, printing as you have:
cout << left << setw(5) << "01234";
cout << left << setw(5) << "56789" << endl;
will result in something which looks like this:
0123456789
I would encourage that you use a larger number, such as 10 in your setw manipulation. This will align your data and prevent you from needing to add spaces, so long as it's larger than your largest value.
I wrote a horrifying test to prove this out:
#include <iostream>
#include <string>
#include <vector>
#include <iomanip>
using namespace std;
int main( int argc, char** argv )
{
vector<int> numbers = { 1, 0, 949, 1, 27282, 949, 27323, 27282, 27324, 27323, 27425, 27324, 27426, 27525 };
vector<string> words =
{
"/sbin/init",
"/usr/sbin/sshd -D -d",
"sshd: salvucwa [ priv]",
"-bash",
"script",
"bash - i"
};
cout << left << setw(10) << numbers[0]
<< setw(10) << numbers[1]
<< setw(50)<< words[0] << endl;
cout << left << setw(10) << numbers[2]
<< setw(10) << numbers[3]
<< setw(50)<< words[1] << endl;
cout << left << setw(10) << numbers[4]
<< setw(10) << numbers[5]
<< setw(50)<< words[2] << endl;
cout << left << setw(10) << numbers[6]
<< setw(10) << numbers[7]
<< setw(50)<< words[3] << endl;
cout << left << setw(10) << numbers[8]
<< setw(10) << numbers[9]
<< setw(50)<< words[4] << endl;
cout << left << setw(10) << numbers[10]
<< setw(10) << numbers[11]
<< setw(50)<< words[5] << endl;
}
This outputs:
1 0 /sbin/init
949 1 /usr/sbin/sshd -D -d
27282 949 sshd: salvucwa [ priv]
27323 27282 -bash
27324 27323 script
27425 27324 bash - i

Answer 2

There are a couple of problems in the posted approach.
It doesn't take into account the real length of the strings, using std::setw(5) and only before pid.
It doesn't consider that the source string may contain more then one space between the fields. For example, "27324 27323 -bash" would be parsed as pid = "27324", ppid = "", cmd = "27323 -bash"
A lot of copies are also unnecessary performed.
A possible implementation that takes care of the previous points may be the following
#include <algorithm>
#include <iostream>
#include <iomanip>
#include <vector>
#include <string>
#include <cctype>
void printData(std::vector<std::string> const& tree)
{
auto is_space = [](char ch) -> bool {
return std::isspace(static_cast<unsigned char>(ch));
};
for (auto row{std::rbegin(tree)}, last_row{std::rend(tree)};
row != last_row; ++row)
{
auto first = std::begin(*row);
auto last = std::end(*row);
auto pid_first = std::find_if_not(first, last, is_space);
auto pid_last = std::find_if(pid_first, last, is_space);
std::string pid(pid_first, pid_last); // You may use a std::string_view
auto ppid_first = std::find_if_not(pid_last, last, is_space);
auto ppid_last = std::find_if(ppid_first, last, is_space);
std::string ppid(ppid_first, ppid_last);
auto cmd_first = std::find_if_not(ppid_last, last, is_space);
std::string cmd(cmd_first, last);
std::cout << std::left << std::setw(8) << pid
<< std::setw(8) << ppid
<< std::setw(50) << cmd << '\n';
}
}