反引号之间执行的程序的termcap

Question

I'm trying to make a C program to select options. It works if I run it this way:

./select choice{1..5}
☐ choice1  ☐ choice3  ☐ choice5
☐ choice2  ☐ choice4

# outputs "choice1 choice2" on stdout

But if I run it between backticks, it's a hell

`./select choice{1..5}` > choices.txt
☐ choice1☐ choice2☐ choice3☐ choice4☐ choice5

# Write "choice1 choice2" in `choices.txt`

I need to be able to retrieve selected options. That is why I've done all my outputs to a file I've opened with

int tty = open("/dev/tty", O_RDWR);
/* Do my program using outputs on fd `tty` */
printf("%s\n", get_results());

I think this is related with the use of tgoto in my code, to move the writing cursor on the screen.

if ((cm = tgetstr("cm", NULL)) == NULL)
    return (-1);
tputs(tgoto(cm, x, y), fd, &my_putchar);
return (0);

I've seen that using isatty(1) returns 0 when executed between backticks, and 1 if executed directly... So, is there a way for me to move the cursor and keep my formating in both situations?

Thank you for your time

Answer 1

The fragment of code shown in the question is using the termcap interface (not curses ). It uses

tputs(tgoto(cm, x, y), fd, &my_putchar);

where my_putchar is likely writing to the standard output, like the rest of the program (using printf ). If the program were altered to write all of its screen output to the standard error, then at the end it could write its result to the standard output, simplifying scripting.

There is no need to open /dev/tty ; rather, replacing

printf("choice%d", n);

by

fprintf(stderr, "choice%d", n);

and of course changing my_putchar to something like

int my_putchar(int c) { return fputc(c, stderr); }

is the way to go.

If this were a curses application, one would change the output streams using newterm rather than initscr . dialog uses newterm , of course.