Sending special characters to pseudo-terminal? - c

Question

I'm trying to write a C program that creates a pseudo-terminal running a new bash instance, and records all the input and output that goes through it. The eventual goal would be to asynchronously send this to a server, where somebody else could view your terminal activity in real time.
I've completed the pseudo-term creation step, and I can start a new bash instance and log "most" of the input and output. My issue right now is that the pseudo-term isn't properly recognizing arrow keys. They get printed to the screen as ASCII values (^[[A, ^[[[B, ^[[C, ^[[D), instead of moving the cursor around the command line.
Here's the slave portion of the pty, which will run bash:
if(pid == 0){ //child
struct termios term_settings;
close(ptyfds.master);
rc = tcgetattr(ptyfds.slave, &term_settings);
cfmakeraw(&term_settings);
tcsetattr(ptyfds.slave, TCSANOW, &term_settings);
//replace stdin,out,err with the slave filedesc
close(0);
close(1);
close(2);
dup(ptyfds.slave);
dup(ptyfds.slave);
dup(ptyfds.slave);
//We can close original fd and use 0,1,2
close(ptyfds.slave);
//Make this process the session lead
setsid();
//Slave side of PTY becomes the new controlling terminal
ioctl(0, TIOCSCTTY, 1);
char ** child_argv = (char **) malloc(argc * sizeof(char*));
int i;
for(i=1; i<argc; i++){
child_argv[i-1] = strdup(argv[i]); //could be bash, bc, python
}
child_argv[i-1] = NULL;
rc = execvp(child_argv[0], child_argv);
}
And here's the master side of the pty, sending input to the slave and capturing its output.
if(pid == 0){ //parent
fd_set fd_in;
close(ptyfds.slave);
FILE *logFile = fopen("./log", "w");
while(1){
//Add stdin and master fd to object
FD_ZERO(&fd_in);
FD_SET(0,&fd_in);
FD_SET(ptyfds.master, &fd_in);
//intercept data from stdin or from slave out (which is redirected to master)
rc = select(ptyfds.master+1, &fd_in, NULL,NULL,NULL);
switch(rc){
case -1:
fprintf(stderr, "Error %d on select()\n", errno);
exit(1);
default:
if (FD_ISSET(0, &fd_in)){ //There's data on stdin
rc = read(0, input, sizeof(input));
if(rc > 0){
input[rc] = '\0';
write(ptyfds.master, input, rc);//send to master -> slave
fputs(input, logFile);
}
else if(rc < 0){
fprintf(stderr, "Error %d on stdin\n", errno);
exit(1);
}
}
if(FD_ISSET(ptyfds.master, &fd_in)){ //There's data from slave
rc = read(ptyfds.master, input, sizeof(input)-1);
if(rc > 0){
input[rc] = '\0';
write(1, input, rc);//send to stdout
fputs(input, logFile);
}
else if (rc < 0){
fprintf(stderr, "Error %d on read master pty\n", errno);
exit(1);
}
}
}//switch
}//while
}//end parent
I've tried messing around with the termios flags here, but there are none that specify arrow keys.
What do I need to do?
Much of this code came from here.

Answer 1

I think there was a mistake in the example program.
I was able to fix it by moving:
rc = tcgetattr(ptyfds.slave, &term_settings);
cfmakeraw(&term_settings);
tcsetattr(ptyfds.slave, TCSANOW, &term_settings);
into the master section and replacing ptyfds.slave with STDIN_FILENO
(This sets STDIN to raw mode, rather than the slave)