【发布时间】：2016-06-05 18:22:17
【问题描述】：
这是我在codereview - Colorful output on terminal 上发布的问题的后续，我试图在终端上输出彩色字符串并通过isatty() 调用检测它。然而正如@Jerry Coffin 指出的那样 -
您使用 isatty 来检查标准输出是否连接到终端，无论您正在写入什么流。这意味着其余函数只有在您将
std::cout作为它们要写入的流传递时才能正常工作。否则，您可能会在写入非 TTY 内容时允许格式化，而您可能会在写入 TTY 内容时禁止格式化。
这是我不知道的事情（读作没有经验），我什至不知道 cin/cout 可以重定向到其他地方。所以我试图阅读更多关于它的内容，并发现了一些关于 SO 的现有问题。这是我一起破解的：
// initialize them at start of program - mandatory
std::streambuf const *coutbuf = std::cout.rdbuf();
std::streambuf const *cerrbuf = std::cerr.rdbuf();
std::streambuf const *clogbuf = std::clog.rdbuf();
// ignore this, just checks for TERM env var
inline bool supportsColor()
{
if(const char *env_p = std::getenv("TERM")) {
const char *const term[8] = {
"xterm", "xterm-256", "xterm-256color", "vt100",
"color", "ansi", "cygwin", "linux"};
for(unsigned int i = 0; i < 8; ++i) {
if(std::strcmp(env_p, term[i]) == 0) return true;
}
}
return false;
}
rightTerm = supportsColor();
// would make necessary checks to ensure in terminal
inline bool isTerminal(const std::streambuf *osbuf)
{
FILE *currentStream = nullptr;
if(osbuf == coutbuf) {
currentStream = stdout;
}
else if(osbuf == cerrbuf || osbuf == clogbuf) {
currentStream = stderr;
}
else {
return false;
}
return isatty(fileno(currentStream));
}
// this would print checking rightTerm && isTerminal calls
inline std::ostream &operator<<(std::ostream &os, rang::style v)
{
std::streambuf const *osbuf = os.rdbuf();
return rightTerm && isTerminal(osbuf)
? os << "\e[" << static_cast<int>(v) << "m"
: os;
}
我的主要问题是，虽然我已经手动测试过，但我不知道这可能会失败的情况或它可能包含的错误。这是做这件事的正确方法吗？有什么我可能遗漏的吗？
这是一个运行的最小示例（您还需要一个带有随机数据的in.txt）：
#include <iostream>
#include <fstream>
#include <string>
#include <unistd.h>
#include <cstdlib>
#include <cstring>
void f();
bool supportsColor();
// sample enum for foreground colors
enum class fg : unsigned char {
def = 39,
black = 30,
red = 31,
green = 32,
yellow = 33,
blue = 34,
magenta = 35,
cyan = 36,
gray = 37
};
// initialize them at start of program - mandatory
// so that even if user redirects, we've a copy
std::streambuf const *coutbuf = std::cout.rdbuf();
std::streambuf const *cerrbuf = std::cerr.rdbuf();
std::streambuf const *clogbuf = std::clog.rdbuf();
// check if TERM supports color
bool rightTerm = supportsColor();
// Here is the implementation of isTerminal
// which checks if program is writing to Terminal or not
bool isTerminal(const std::streambuf *osbuf)
{
FILE *currentStream = nullptr;
if(osbuf == coutbuf) {
currentStream = stdout;
}
else if(osbuf == cerrbuf || osbuf == clogbuf) {
currentStream = stderr;
}
else {
return false;
}
return isatty(fileno(currentStream));
}
// will check if TERM supports color and isTerminal()
inline std::ostream &operator<<(std::ostream &os, fg v)
{
std::streambuf const *osbuf = os.rdbuf();
return rightTerm && isTerminal(osbuf)
? os << "\e[" << static_cast<int>(v) << "m"
: os;
}
int main()
{
std::cout << fg::red << "ERROR HERE! " << std::endl
<< fg::blue << "ERROR INVERSE?" << std::endl;
std::ifstream in("in.txt");
std::streambuf *Orig_cinbuf = std::cin.rdbuf(); // save old buf
std::cin.rdbuf(in.rdbuf()); // redirect std::cin to in.txt!
std::ofstream out("out.txt");
std::streambuf *Orig_coutbuf = std::cout.rdbuf(); // save old buf
std::cout.rdbuf(out.rdbuf()); // redirect std::cout to out.txt!
std::string word;
std::cin >> word; // input from the file in.txt
std::cout << fg::blue << word << " "; // output to the file out.txt
f(); // call function
std::cin.rdbuf(Orig_cinbuf); // reset to standard input again
std::cout.rdbuf(Orig_coutbuf); // reset to standard output again
std::cin >> word; // input from the standard input
std::cout << word; // output to the standard input
return 0;
}
void f()
{
std::string line;
while(std::getline(std::cin, line)) // input from the file in.txt
{
std::cout << fg::green << line << "\n"; // output to the file out.txt
}
}
bool supportsColor()
{
if(const char *env_p = std::getenv("TERM")) {
const char *const term[8] = {"xterm", "xterm-256", "xterm-256color",
"vt100", "color", "ansi",
"cygwin", "linux"};
for(unsigned int i = 0; i < 8; ++i) {
if(std::strcmp(env_p, term[i]) == 0) return true;
}
}
return false;
}
我还标记了c 语言，虽然这是c++ 代码，因为相关代码是黑白共享的，我不想错过任何建议
【问题讨论】：
-
请尽量减少代码，只有相关部分应该这样做
-
您可以使用
test | less或test > test.txt之类的东西进行测试。 -
@tadman ^ 回答“问题”。
-
@tadman 直到我在此页面中看到
function included in multiple source files must be inline- en.cppreference.com/w/cpp/language/inline 之前，我并没有经常使用内联。 -
@tadman,
inline只是与性能间接相关，这意味着函数体可以出现在多个翻译单元中（即在标题中）而不会出现多个定义错误。