Linux程序设计第四版笔记
1：5.2节中与终端进⾏对话
如果不希望程序中与⽤户交互的部分被重定向，单允许其他的输⼊和输出呗重定向，你就需要将与⽤户交互的部分与stdout和stderr分开，因此，可以直接对/dev/tty进⾏读写，该设备始终指向当前终端或当前的登录会话。代码如下：
#include <stdio.h>
#include <unistd.h>
char *menu[] = {
"a - add new record",
"d - delete record",
"q - quit",
NULL,
};
int getchoice(char *greet, char *choices[], FILE *in, FILE *out);
int main()
{
int choice = 0;
FILE *input;
FILE *output;
if (!isatty(fileno(stdout))) {
fprintf(stderr,"You are not a terminal, OK.\n");
}
input = fopen("/dev/tty", "r");
output = fopen("/dev/tty", "w");
if(!input || !output) {
fprintf(stderr,"Unable to open /dev/tty\n");
exit(1);
}
do {
choice = getchoice("Please select an action", menu, input, output);
printf("You have chosen: %c\n", choice);
} while (choice != 'q');
exit(0);
}
int getchoice(char *greet, char *choices[], FILE *in, FILE *out)
{
int chosen = 0;
int selected;
char **option;
do {
fprintf(out,"Choice: %s\n",greet);
option = choices;
while(*option) {
fprintf(out,"%s\n",*option);
option++;
}
do {
selected = fgetc(in);
} while (selected == '\n');
option = choices;
while(*option) {
if(selected == *option[0]) {
chosen = 1;
break;
break;
}
option++;
linux重定向
}
if(!chosen) {
fprintf(out,"Incorrect choice, select again\n");
}
} while(!chosen);
return selected;
}
执⾏效果：
$ ./a.out >file
You are not a terminal, OK.
Choice: Please select an action
a - add new record
d - delet
e record
q - quit
d
Choice: Please select an action
a - add new record
d - delet
e record
q - quit
q
$ cat file
You have chosen: d
You have chosen: q
$
源码解析：
其实就是把不需要重定向的信息，即仍然要显⽰在屏幕上的信息显⽰在设备/dev/tty中，⽽本来通过stdin/stdout/stderr的信息就重定向到file⽂件中了，不显⽰到屏幕上。

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