我在写一个命令行小程序，我想在interactive shell中，按top的样式刷新屏幕，而如果输出被重定向到文件，则去掉各类颜色、清屏、\r之类的输出。 所以我搜了一下怎么判断当前是不是处于一个interactive shell中的方法，在stackoverflow中有好多方法，这里记录一下.

https://unix.stackexchange.com/questions/26676/how-to-check-if-a-shell-is-login-interactive-batch

通过tty判断

if tty -s
then
    echo Terminal
else
    echo Not on a terminal
fi

或

if [ "`tty`" != "not a tty" ]; then
    echo Terminal
fi

通过$-判断

case $- in
  *i*) echo "This shell is interactive";;
  *) echo "This is a script";;
esac

而什么是$-呢？

根据这个链接:

$- prints The current set of options in your current shell.

himBH means following options are enabled:

H - histexpand m - monitor h - hashall B - braceexpand i - interactive

如何在C/C++代码里判断？

C语言中获取环境变量的办法

#include <stdlib.h>
#include <stdio.h>

int main(void)
{
    char *pathvar;
    pathvar = getenv("PATH");
    printf("pathvar=%s",pathvar);
    return 0;
}

然而$-不是一个环境变量。你可以用SHELL这个环境变量。

istty

NAME top isatty - test whether a file descriptor refers to a terminal SYNOPSIS top #include

int isatty(int fd); DESCRIPTION         top
The isatty() function tests whether fd is an open file descriptor
referring to a terminal. RETURN VALUE         top
isatty() returns 1 if fd is an open file descriptor referring to
a terminal; otherwise 0 is returned, and errno is set to indicate
the error. ```c #include <unistd.h> int is_redirected(){    if (!isatty(fileno(stdout))){
   fprintf(stdout, "argv, argc, someone is redirecting me elsewhere...\n");
   return 1;    }    return 0; }

```