Task: Append a record to the end of a text file
C++: #include <iostream>
#include <fstream>
#include <string>
#include <vector>

std::ostream& operator<<(std::ostream& out, const std::string s) {
    return out << s.c_str();
}

struct gecos_t {
    std::string fullname, office, extension, homephone, email;

    friend std::ostream& operator<<(std::ostream&, const gecos_t&);
};

std::ostream& operator<<(std::ostream& out, const gecos_t& g) {
    return out << g.fullname << ',' << g.office << ',' << g.extension << ',' << g.homephone << ',' << g.email;
}

struct passwd_t {
    std::string account, password;
    int uid, gid;
    gecos_t gecos;
    std::string directory, shell;

    passwd_t(const std::string& a, const std::string& p, int u, int g, const gecos_t& ge, const std::string& d, const std::string& s)
        : account(a), password(p), uid(u), gid(g), gecos(ge), directory(d), shell(s)
    {
        
    }

    friend std::ostream& operator<<(std::ostream&, const passwd_t&);
};

std::ostream& operator<<(std::ostream& out, const passwd_t& p) {
    return out << p.account << ':' << p.password << ':' << p.uid << ':' << p.gid << ':' << p.gecos << ':' << p.directory << ':' << p.shell;
}

std::vector<passwd_t> passwd_list{
    {
        "jsmith", "x", 1001, 1000,
        {"Joe Smith", "Room 1007", "(234)555-8917", "(234)555-0077", "jsmith@rosettacode.org"},
        "/home/jsmith", "/bin/bash"
    },
    {
        "jdoe", "x", 1002, 1000,
        {"Jane Doe", "Room 1004", "(234)555-8914", "(234)555-0044", "jdoe@rosettacode.org"},
        "/home/jdoe", "/bin/bash"
    }
};

int main() {
    
    std::ofstream out_fd("passwd.txt");
    for (size_t i = 0; i < passwd_list.size(); ++i) {
        out_fd << passwd_list[i] << '\n';
    }
    out_fd.close();

    
    out_fd.open("passwd.txt", std::ios::app);
    out_fd << passwd_t("xyz", "x", 1003, 1000, { "X Yz", "Room 1003", "(234)555-8913", "(234)555-0033", "xyz@rosettacode.org" }, "/home/xyz", "/bin/bash") << '\n';
    out_fd.close();

    
    std::ifstream in_fd("passwd.txt");
    std::string line, temp;
    while (std::getline(in_fd, temp)) {
        
        if (!temp.empty()) {
            line = temp;
        }
    }
    if (line.substr(0, 4) == "xyz:") {
        std::cout << "Appended record: " << line << '\n';
    } else {
        std::cout << "Failed to find the expected record appended.\n";
    }

    return 0;
}

Go: package main

import (
    "bytes"
    "fmt"
    "io"
    "io/ioutil"
    "os"
)

type pw struct {
    account, password string
    uid, gid          uint
    gecos
    directory, shell string
}

type gecos struct {
    fullname, office, extension, homephone, email string
}

func (p *pw) encode(w io.Writer) (int, error) {
    return fmt.Fprintf(w, "%s:%s:%d:%d:%s,%s,%s,%s,%s:%s:%s\n",
        p.account, p.password, p.uid, p.gid,
        p.fullname, p.office, p.extension, p.homephone, p.email,
        p.directory, p.shell)
}


var p2 = []pw{
    {"jsmith", "x", 1001, 1000, gecos{"Joe Smith", "Room 1007",
        "(234)555-8917", "(234)555-0077", "jsmith@rosettacode.org"},
        "/home/jsmith", "/bin/bash"},
    {"jdoe", "x", 1002, 1000, gecos{"Jane Doe", "Room 1004",
        "(234)555-8914", "(234)555-0044", "jdoe@rosettacode.org"},
        "/home/jsmith", "/bin/bash"},
}

var pa = pw{"xyz", "x", 1003, 1000, gecos{"X Yz", "Room 1003",
    "(234)555-8913", "(234)555-0033", "xyz@rosettacode.org"},
    "/home/xyz", "/bin/bash"}

var expected = "xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913," +
    "(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash"

const pfn = "mythical"

func main() {
    writeTwo()
    appendOneMore()
    checkResult()
}

func writeTwo() {
    
    f, err := os.Create(pfn)
    if err != nil {
        fmt.Println(err)
        return
    }
    defer func() {
        if cErr := f.Close(); cErr != nil && err == nil {
            fmt.Println(cErr)
        }
    }()
    for _, p := range p2 {
        if _, err = p.encode(f); err != nil {
            fmt.Println(err)
            return
        }
    }
}

func appendOneMore() {
    
    f, err := os.OpenFile(pfn, os.O_RDWR|os.O_APPEND, 0)
    if err != nil {
        fmt.Println(err)
        return
    }
    if _, err := pa.encode(f); err != nil {
        fmt.Println(err)
    }
    if cErr := f.Close(); cErr != nil && err == nil {
        fmt.Println(cErr)
    }
}

func checkResult() {
    
    b, err := ioutil.ReadFile(pfn)
    if err != nil {
        fmt.Println(err)
        return
    }
    if string(bytes.Split(b, []byte{'\n'})[2]) == expected {
        fmt.Println("append okay")
    } else {
        fmt.Println("it didn't work")
    }
}