very simple serial terminal

com.c

/*
 * Building: cc -o com com.c
 * Usage   : ./com /dev/device [speed]
 * Example : ./com /dev/ttyS0 [115200]
 * Keys    : Ctrl-A - exit, Ctrl-X - display control lines status
 * Darcs   : darcs get http://tinyserial.sf.net/
 * Homepage: http://tinyserial.sourceforge.net
 * Version : 2007-07-31
 *
 * Ivan Tikhonov, http://www.brokestream.com, [email protected]
 * Patches by Jim Kou ([email protected]) and Henry Nestler
 * CR->CRLF conversion by Bjoern Riemer <bjoern.riemer_@_web.de>
 * OS X fix by Alexander Willner <[email protected]>
 *
 */


/* Copyright (C) 2007 Ivan Tikhonov

  This software is provided 'as-is', without any express or implied
  warranty.  In no event will the authors be held liable for any damages
  arising from the use of this software.

  Permission is granted to anyone to use this software for any purpose,
  including commercial applications, and to alter it and redistribute it
  freely, subject to the following restrictions:

  1. The origin of this software must not be misrepresented; you must not
     claim that you wrote the original software. If you use this software
     in a product, an acknowledgment in the product documentation would be
     appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be
     misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.

  Ivan Tikhonov, [email protected]

*/

#include <termios.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/signal.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#include <fcntl.h>

/* fix: not defined in SUSv3, therefore not in OS X */
#ifndef B921600
#define B921600	921600
#endif

int transfer_byte(int from, int to, int is_control, int *addcr);

typedef struct {char *name; int flag; } speed_spec;


void print_status(int fd,int addcr) {
	int status;
	unsigned int arg;
	status = ioctl(fd, TIOCMGET, &arg);
	fprintf(stderr, "[STATUS]: ");
	if(arg & TIOCM_RTS) fprintf(stderr, "RTS ");
	if(arg & TIOCM_CTS) fprintf(stderr, "CTS ");
	if(arg & TIOCM_DSR) fprintf(stderr, "DSR ");
	if(arg & TIOCM_CAR) fprintf(stderr, "DCD ");
	if(arg & TIOCM_DTR) fprintf(stderr, "DTR ");
	if(arg & TIOCM_RNG) fprintf(stderr, "RI ");
	if(addcr) fprintf(stderr,"[LF->CRLF]");
	fprintf(stderr, "\r\n");
}

int main(int argc, char *argv[])
{
	int comfd;
	struct termios oldtio, newtio;       //place for old and new port settings for serial port
	struct termios oldkey, newkey;       //place tor old and new port settings for keyboard teletype
	char *devicename = argv[1];
	int need_exit = 0;
	int addcr = 0;
	speed_spec speeds[] =
	{
		{"1200", B1200},
		{"2400", B2400},
		{"4800", B4800},
		{"9600", B9600},
		{"19200", B19200},
		{"38400", B38400},
		{"57600", B57600},
		{"115200", B115200},
		{"921600", B921600},
		{NULL, 0}
	};
	int speed = B9600;

	if(argc < 2) {
		fprintf(stderr, "example: %s /dev/ttyS0 [115200]\n", argv[0]);
		exit(1);
	}

	comfd = open(devicename, O_RDWR | O_NOCTTY | O_NONBLOCK);
	if (comfd < 0)
	{
		perror(devicename);
		exit(-1);
	}

	if(argc > 2) {	
		speed_spec *s;
		for(s = speeds; s->name; s++) {
			if(strcmp(s->name, argv[2]) == 0) {
				speed = s->flag;
				fprintf(stderr, "setting speed %s\n", s->name);
				break;
			}
		}
	}

	fprintf(stderr, "C-a exit, C-x modem lines status, C-w toggle LF->CRLF\n");

	tcgetattr(STDIN_FILENO,&oldkey);
	newkey.c_cflag = B9600 | CRTSCTS | CS8 | CLOCAL | CREAD;
	newkey.c_iflag = IGNPAR;
	newkey.c_oflag = 0;
	newkey.c_lflag = 0;
	newkey.c_cc[VMIN]=1;
	newkey.c_cc[VTIME]=0;
	tcflush(STDIN_FILENO, TCIFLUSH);
	tcsetattr(STDIN_FILENO,TCSANOW,&newkey);


	tcgetattr(comfd,&oldtio); // save current port settings 
	newtio.c_cflag = speed | CS8 | CREAD;
	newtio.c_iflag = IGNPAR;
	newtio.c_oflag = 0;
	newtio.c_lflag = 0;
	newtio.c_cc[VMIN]=1;
	newtio.c_cc[VTIME]=0;
	tcflush(comfd, TCIFLUSH);
	tcsetattr(comfd,TCSANOW,&newtio);

	print_status(comfd,addcr);

	while(!need_exit) {
		fd_set fds;
		int ret;
		
		FD_ZERO(&fds);
		FD_SET(STDIN_FILENO, &fds);
		FD_SET(comfd, &fds);


		ret = select(comfd+1, &fds, NULL, NULL, NULL);
		if(ret == -1) {
			perror("select");
		} else if (ret > 0) {
			if(FD_ISSET(STDIN_FILENO, &fds)) {
				need_exit = transfer_byte(STDIN_FILENO, comfd, 1, &addcr);
			} else if(FD_ISSET(comfd, &fds)) {
				need_exit = transfer_byte(comfd, STDIN_FILENO, 0, &addcr);
			}
		}
	}

	tcsetattr(comfd,TCSANOW,&oldtio);
	tcsetattr(STDIN_FILENO,TCSANOW,&oldkey);
	close(comfd);

	return 0;
}


int transfer_byte(int from, int to, int is_control, int *addcr) {
	char c;
	char cr='\r';
	int ret;
	ret = read(from, &c, 1);
	if(ret == 1) {
		if(is_control) {
			if(c == '\x01') { // C-a
				return -1;
			} else if(c == '\x18') { // C-x
				print_status(to, *addcr);
				return 0;
			} else if(c == '\x17' || c == '\x13') { // C-w //C-s
				//fprintf(stderr,"[LF->CRLF]\r\n");
				(*addcr) = (*addcr) ? 0 : 1;
				print_status(to, *addcr);
				return 0;
			}
		}
		if(write(to, &c, 1) != 1) {
			perror("write failed");
		}
		if (c=='\n' && (*addcr))
			if(write(to, &cr, 1) != 1) {
				perror("write failed");
			}
	} else {
		fprintf(stderr, "nothing to read. probably port disconnected.\n");
		return -2;
	}
	return 0;
}