pipe into a curses program
The library ncurses provides an interactive user interface. However, I was wondering what would happen if you pipe something into the program. So i tried like this:
# echo foo | my_curses_prog
It seems there is always input pending on stdin but getch cannot read anything. So what's happening under the hood?
Updated test program:
#include <ncurses.h>
int main()
{
WINDOW *win = initscr();
nodelay(win, 0);
refresh();
FILE *fp = fopen("my_curses_prog.log", "w");
while (1) {
int ch = getch();
fprintf(fp, "%dn", ch);
fflush(fp);
}
fclose(fp);
endwin();
return 0;
}
terminal pipe ncurses
asked Dec 17 at 9:59
Cyker
1,36121429
add a comment |
The library ncurses provides an interactive user interface. However, I was wondering what would happen if you pipe something into the program. So i tried like this:
# echo foo | my_curses_prog
It seems there is always input pending on stdin but getch cannot read anything. So what's happening under the hood?
Updated test program:
#include <ncurses.h>
int main()
{
WINDOW *win = initscr();
nodelay(win, 0);
refresh();
FILE *fp = fopen("my_curses_prog.log", "w");
while (1) {
int ch = getch();
fprintf(fp, "%dn", ch);
fflush(fp);
}
fclose(fp);
endwin();
return 0;
}
terminal pipe ncurses
asked Dec 17 at 9:59
Cyker
1,36121429
add a comment |
The library ncurses provides an interactive user interface. However, I was wondering what would happen if you pipe something into the program. So i tried like this:
# echo foo | my_curses_prog
It seems there is always input pending on stdin but getch cannot read anything. So what's happening under the hood?
Updated test program:
#include <ncurses.h>
int main()
{
WINDOW *win = initscr();
nodelay(win, 0);
refresh();
FILE *fp = fopen("my_curses_prog.log", "w");
while (1) {
int ch = getch();
fprintf(fp, "%dn", ch);
fflush(fp);
}
fclose(fp);
endwin();
return 0;
}
terminal pipe ncurses
asked Dec 17 at 9:59
Cyker
1,36121429
The library ncurses provides an interactive user interface. However, I was wondering what would happen if you pipe something into the program. So i tried like this:
# echo foo | my_curses_prog
It seems there is always input pending on stdin but getch cannot read anything. So what's happening under the hood?
Updated test program:
#include <ncurses.h>
int main()
{
WINDOW *win = initscr();
nodelay(win, 0);
refresh();
FILE *fp = fopen("my_curses_prog.log", "w");
while (1) {
int ch = getch();
fprintf(fp, "%dn", ch);
fflush(fp);
}
fclose(fp);
endwin();
return 0;
}
terminal pipe ncurses
terminal pipe ncurses
asked Dec 17 at 9:59
Cyker
1,36121429
asked Dec 17 at 9:59
Cyker
1,36121429
edited Dec 17 at 12:16
asked Dec 17 at 9:59
Cyker
1,36121429
asked Dec 17 at 9:59
Cyker
1,36121429
asked Dec 17 at 9:59
Cyker
1,36121429
1,36121429
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
curses applications can be initialized using initscr or newterm. The former reads stdin only; the latter can be told to use a different input. If you want to have a curses application reading from a pipe, you would use newterm (dialog does this).
curses expects its input to be a terminal. A pipe is never going to act like a terminal, since it is buffered, cannot be changed to raw mode using the standard terminal I/O calls. Since its input is buffered, you don't see much useful happening with getch until it is able to read the whole buffer (lots of characters, or until a newline, depending on how you're testing).
answered Dec 17 at 10:22
Thomas Dickey
52k594164
OK my bad. I'm only using stdin so I thinkinitscrshould work. Yeah, it actually gets those input characters when fd0 is a pipe. But the problem with a pipe is that whengetchhits EOF, it keeps returning -1 instead of blocking (even ifnodelayis false). So there is no input pending but EOF keeps givinggetchERR. I think this is probably due to some internalselectcall in ncurses which reports a fd as ready on EOF. Well, I thought I could test my curses application by piping in keystrokes, now there's a caveat.
– Cyker
Dec 17 at 12:15
add a comment |
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
curses applications can be initialized using initscr or newterm. The former reads stdin only; the latter can be told to use a different input. If you want to have a curses application reading from a pipe, you would use newterm (dialog does this).
curses expects its input to be a terminal. A pipe is never going to act like a terminal, since it is buffered, cannot be changed to raw mode using the standard terminal I/O calls. Since its input is buffered, you don't see much useful happening with getch until it is able to read the whole buffer (lots of characters, or until a newline, depending on how you're testing).
answered Dec 17 at 10:22
Thomas Dickey
52k594164
OK my bad. I'm only using stdin so I thinkinitscrshould work. Yeah, it actually gets those input characters when fd0 is a pipe. But the problem with a pipe is that whengetchhits EOF, it keeps returning -1 instead of blocking (even ifnodelayis false). So there is no input pending but EOF keeps givinggetchERR. I think this is probably due to some internalselectcall in ncurses which reports a fd as ready on EOF. Well, I thought I could test my curses application by piping in keystrokes, now there's a caveat.
– Cyker
Dec 17 at 12:15
add a comment |
curses applications can be initialized using initscr or newterm. The former reads stdin only; the latter can be told to use a different input. If you want to have a curses application reading from a pipe, you would use newterm (dialog does this).
curses expects its input to be a terminal. A pipe is never going to act like a terminal, since it is buffered, cannot be changed to raw mode using the standard terminal I/O calls. Since its input is buffered, you don't see much useful happening with getch until it is able to read the whole buffer (lots of characters, or until a newline, depending on how you're testing).
answered Dec 17 at 10:22
Thomas Dickey
52k594164
OK my bad. I'm only using stdin so I thinkinitscrshould work. Yeah, it actually gets those input characters when fd0 is a pipe. But the problem with a pipe is that whengetchhits EOF, it keeps returning -1 instead of blocking (even ifnodelayis false). So there is no input pending but EOF keeps givinggetchERR. I think this is probably due to some internalselectcall in ncurses which reports a fd as ready on EOF. Well, I thought I could test my curses application by piping in keystrokes, now there's a caveat.
– Cyker
Dec 17 at 12:15
add a comment |
curses applications can be initialized using initscr or newterm. The former reads stdin only; the latter can be told to use a different input. If you want to have a curses application reading from a pipe, you would use newterm (dialog does this).
curses expects its input to be a terminal. A pipe is never going to act like a terminal, since it is buffered, cannot be changed to raw mode using the standard terminal I/O calls. Since its input is buffered, you don't see much useful happening with getch until it is able to read the whole buffer (lots of characters, or until a newline, depending on how you're testing).
answered Dec 17 at 10:22
Thomas Dickey
52k594164
curses applications can be initialized using initscr or newterm. The former reads stdin only; the latter can be told to use a different input. If you want to have a curses application reading from a pipe, you would use newterm (dialog does this).
curses expects its input to be a terminal. A pipe is never going to act like a terminal, since it is buffered, cannot be changed to raw mode using the standard terminal I/O calls. Since its input is buffered, you don't see much useful happening with getch until it is able to read the whole buffer (lots of characters, or until a newline, depending on how you're testing).
answered Dec 17 at 10:22
Thomas Dickey
52k594164
answered Dec 17 at 10:22
Thomas Dickey
52k594164
answered Dec 17 at 10:22
Thomas Dickey
52k594164
answered Dec 17 at 10:22
Thomas Dickey
52k594164
52k594164
OK my bad. I'm only using stdin so I thinkinitscrshould work. Yeah, it actually gets those input characters when fd0 is a pipe. But the problem with a pipe is that whengetchhits EOF, it keeps returning -1 instead of blocking (even ifnodelayis false). So there is no input pending but EOF keeps givinggetchERR. I think this is probably due to some internalselectcall in ncurses which reports a fd as ready on EOF. Well, I thought I could test my curses application by piping in keystrokes, now there's a caveat.
– Cyker
Dec 17 at 12:15
add a comment |
OK my bad. I'm only using stdin so I thinkinitscrshould work. Yeah, it actually gets those input characters when fd0 is a pipe. But the problem with a pipe is that whengetchhits EOF, it keeps returning -1 instead of blocking (even ifnodelayis false). So there is no input pending but EOF keeps givinggetchERR. I think this is probably due to some internalselectcall in ncurses which reports a fd as ready on EOF. Well, I thought I could test my curses application by piping in keystrokes, now there's a caveat.
– Cyker
Dec 17 at 12:15
OK my bad. I'm only using stdin so I think
initscr should work. Yeah, it actually gets those input characters when fd0 is a pipe. But the problem with a pipe is that when getch hits EOF, it keeps returning -1 instead of blocking (even if nodelay is false). So there is no input pending but EOF keeps giving getch ERR. I think this is probably due to some internal select call in ncurses which reports a fd as ready on EOF. Well, I thought I could test my curses application by piping in keystrokes, now there's a caveat.– Cyker
Dec 17 at 12:15
OK my bad. I'm only using stdin so I think
initscr should work. Yeah, it actually gets those input characters when fd0 is a pipe. But the problem with a pipe is that when getch hits EOF, it keeps returning -1 instead of blocking (even if nodelay is false). So there is no input pending but EOF keeps giving getch ERR. I think this is probably due to some internal select call in ncurses which reports a fd as ready on EOF. Well, I thought I could test my curses application by piping in keystrokes, now there's a caveat.– Cyker
Dec 17 at 12:15
add a comment |
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