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#problem with pipes and processes
hexed sparrowBOT
ocean phoenix
One solution is to have pong send a message to ping to print something to the terminal
Alternatively, dup stdout to another file descriptor BEFORE overwriting with the pipe
Or just have the pipe not overwrite stdout and write to the pipe descriptor directly
swift nimbus
One solution is to have pong send a message to ping to print something to the te...
yes, but they don't let us do it.
swift nimbus
Or just have the pipe not overwrite stdout and write to the pipe descriptor dire...
It is a requirement to connect the STDOUT and the STDIN to pipe1 and pipe2
ocean phoenix
Then dup STDOUT to a new file descriptor before overwriting it with the pipe
swift nimbus
But when I close it to write through the pipe again, then I won't be able to write through the terminal again, right?
ocean phoenix
One moment
;compile
#include <unistd.h>
int main() {
int newstdout = dup(STDOUT_FILENO);
close(STDOUT_FILENO);
write(newstdout, "Hello World\n", 12);
}
rocky condorBOT
ocean phoenix
Forwarding the new descriptor to PONG might be difficult, though you might be able to use a constant for that
;compile
#include <unistd.h>
int main() {
int newstdout = 10;
dup2(STDOUT_FILENO, newstdout);
close(STDOUT_FILENO);
write(newstdout, "Hello World\n", 12);
}
So you propose that the child, when it has to be shown through the terminal, makes a dup2 and when it wants to send it through the terminal it makes another dup2 with the other decryptor, is that correct?
ocean phoenix
One dup2 to preserve stdout in another file descriptor that can be used whenever the child wants to print to the terminal.
THen the regulard dup2's to move the pipes
modern blade
yes, but they don't let us do it.
bruh,
call write and use the stderr file descriptor to print the text
modern blade
;compile
```c
#include <unistd.h>
int main() {
int newstdout = 10;
dup2...
why are you overengineering this, the answer is obvious, use stderr to print the text on the screen
ocean phoenix
If it were just one's own personal project, then sure, why not
modern blade
If it were just one's own personal project, then sure, why not
what you wrote is needed in cases where the goal is to redirect stdout to something, let it run, and then restore stdout back to file descriptor 1, I would chose to leave fd 1 untouched and instead open the pipe with fd 3,4, etc, and use those
oh wait, you run execv
ocean phoenix
All I did was show that you can maintain a handle to stdout, while still overwriting fd 1.
From what I gathered, the assignment wanted him to have the pipe point the fd 1, while also wanting to print to the terminal.
I figured it is a resonable to expect the teacher wants to print via stdout as opposed to stderr
modern blade
so, the child process just, dies in the end
ocean phoenix
file descriptors are perserved through execve
modern blade
file descriptors are perserved through execve
the child process uses fd 1, so you gotta prepare fd 1 before you fork and exec
ocean phoenix
yes
hexed sparrowBOT
swift nimbus
!solved
hexed sparrowBOT