# `do`-`while` loop

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Conditionally executes a statement repeatedly (at least once).

### Syntax

attr﻿(optional) `do` statement `while (` expression `);` |  |

attr | - | (since C++11) any number of attributes
expression | - | an expression
statement | - | a statement (typically a compound statement)

### Explanation

When control reaches a do statement, its statement will be executed unconditionally.

Every time statement finishes its execution, expression will be evaluated and contextually converted to bool. If the result is true, statement will be executed again.

If the loop needs to be terminated within statement, a break statement can be used as terminating statement.

If the current iteration needs to be terminated within statement, a continue statement can be used as shortcut.

### Notes

As part of the C++ forward progress guarantee, the behavior is undefined if a loop that is not a trivial infinite loop (since C++26) without observable behavior does not terminate. Compilers are permitted to remove such loops.

### Keywords

`do`, `while`

### Example

Run this code

    #include <algorithm>
    #include <iostream>
    #include <string>

    int main()
    {
        int j = 2;
        do // compound statement is the loop body
        {
            j += 2;
            std::cout << j << ' ';
        }
        while (j < 9);
        std::cout << '\n';

        // common situation where do-while loop is used
        std::string s = "aba";
        std::sort(s.begin(), s.end());

        do std::cout << s << '\n'; // expression statement is the loop body
        while (std::next_permutation(s.begin(), s.end()));
    }

Output:

    4 6 8 10
    aab
    aba
    baa

### See also

C documentation for do-while

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