libbb/xfuncs.c - codeaurora/busybox - Gitiles

 /* vi: set sw=4 ts=4: */
 /*
  * Utility routines.
  *
  * Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
  * Copyright (C) 2006 Rob Landley
  * Copyright (C) 2006 Denys Vlasenko
  *
  * Licensed under GPLv2, see file LICENSE in this source tree.
  */

 /* We need to have separate xfuncs.c and xfuncs_printf.c because
  * with current linkers, even with section garbage collection,
  * if *.o module references any of XXXprintf functions, you pull in
  * entire printf machinery. Even if you do not use the function
  * which uses XXXprintf.
  *
  * xfuncs.c contains functions (not necessarily xfuncs)
  * which do not pull in printf, directly or indirectly.
  * xfunc_printf.c contains those which do.
  *
  * TODO: move xmalloc() and xatonum() here.
  */

 #include "libbb.h"

 /* Turn on nonblocking I/O on a fd */
 int FAST_FUNC ndelay_on(int fd)
 {
 	int flags = fcntl(fd, F_GETFL);
 	if (flags & O_NONBLOCK)
 		return flags;
 	fcntl(fd, F_SETFL, flags | O_NONBLOCK);
 	return flags;
 }

 int FAST_FUNC ndelay_off(int fd)
 {
 	int flags = fcntl(fd, F_GETFL);
 	if (!(flags & O_NONBLOCK))
 		return flags;
 	fcntl(fd, F_SETFL, flags & ~O_NONBLOCK);
 	return flags;
 }

 void FAST_FUNC close_on_exec_on(int fd)
 {
 	fcntl(fd, F_SETFD, FD_CLOEXEC);
 }

 char* FAST_FUNC strncpy_IFNAMSIZ(char *dst, const char *src)
 {
 #ifndef IFNAMSIZ
 	enum { IFNAMSIZ = 16 };
 #endif
 	return strncpy(dst, src, IFNAMSIZ);
 }


 /* Convert unsigned integer to ascii, writing into supplied buffer.
  * A truncated result contains the first few digits of the result ala strncpy.
  * Returns a pointer past last generated digit, does _not_ store NUL.
  */
 void BUG_sizeof(void);
 char* FAST_FUNC utoa_to_buf(unsigned n, char *buf, unsigned buflen)
 {
 	unsigned i, out, res;

 	if (buflen) {
 		out = 0;
 		if (sizeof(n) == 4)
 		// 2^32-1 = 4294967295
 			i = 1000000000;
 #if UINT_MAX > 4294967295 /* prevents warning about "const too large" */
 		else
 		if (sizeof(n) == 8)
 		// 2^64-1 = 18446744073709551615
 			i = 10000000000000000000;
 #endif
 		else
 			BUG_sizeof();
 		for (; i; i /= 10) {
 			res = n / i;
 			n = n % i;
 			if (res || out || i == 1) {
 				if (--buflen == 0)
 					break;
 				out++;
 				*buf++ = '0' + res;
 			}
 		}
 	}
 	return buf;
 }

 /* Convert signed integer to ascii, like utoa_to_buf() */
 char* FAST_FUNC itoa_to_buf(int n, char *buf, unsigned buflen)
 {
 	if (!buflen)
 		return buf;
 	if (n < 0) {
 		n = -n;
 		*buf++ = '-';
 		buflen--;
 	}
 	return utoa_to_buf((unsigned)n, buf, buflen);
 }

 // The following two functions use a static buffer, so calling either one a
 // second time will overwrite previous results.
 //
 // The largest 32 bit integer is -2 billion plus NUL, or 1+10+1=12 bytes.
 // It so happens that sizeof(int) * 3 is enough for 32+ bit ints.
 // (sizeof(int) * 3 + 2 is correct for any width, even 8-bit)

 static char local_buf[sizeof(int) * 3];

 /* Convert unsigned integer to ascii using a static buffer (returned). */
 char* FAST_FUNC utoa(unsigned n)
 {
 	*(utoa_to_buf(n, local_buf, sizeof(local_buf) - 1)) = '\0';

 	return local_buf;
 }

 /* Convert signed integer to ascii using a static buffer (returned). */
 char* FAST_FUNC itoa(int n)
 {
 	*(itoa_to_buf(n, local_buf, sizeof(local_buf) - 1)) = '\0';

 	return local_buf;
 }

 /* Emit a string of hex representation of bytes */
 char* FAST_FUNC bin2hex(char *p, const char *cp, int count)
 {
 	while (count) {
 		unsigned char c = *cp++;
 		/* put lowercase hex digits */
 		*p++ = 0x20 | bb_hexdigits_upcase[c >> 4];
 		*p++ = 0x20 | bb_hexdigits_upcase[c & 0xf];
 		count--;
 	}
 	return p;
 }

 /* Convert "[x]x[:][x]x[:][x]x[:][x]x" hex string to binary, no more than COUNT bytes */
 char* FAST_FUNC hex2bin(char *dst, const char *str, int count)
 {
 	errno = EINVAL;
 	while (*str && count) {
 		uint8_t val;
 		uint8_t c = *str++;
 		if (isdigit(c))
 			val = c - '0';
 		else if ((c|0x20) >= 'a' && (c|0x20) <= 'f')
 			val = (c|0x20) - ('a' - 10);
 		else
 			return NULL;
 		val <<= 4;
 		c = *str;
 		if (isdigit(c))
 			val |= c - '0';
 		else if ((c|0x20) >= 'a' && (c|0x20) <= 'f')
 			val |= (c|0x20) - ('a' - 10);
 		else if (c == ':' || c == '\0')
 			val >>= 4;
 		else
 			return NULL;

 		*dst++ = val;
 		if (c != '\0')
 			str++;
 		if (*str == ':')
 			str++;
 		count--;
 	}
 	errno = (*str ? ERANGE : 0);
 	return dst;
 }

 /* Return how long the file at fd is, if there's any way to determine it. */
 #ifdef UNUSED
 off_t FAST_FUNC fdlength(int fd)
 {
 	off_t bottom = 0, top = 0, pos;
 	long size;

 	// If the ioctl works for this, return it.

 	if (ioctl(fd, BLKGETSIZE, &size) >= 0) return size*512;

 	// FIXME: explain why lseek(SEEK_END) is not used here!

 	// If not, do a binary search for the last location we can read.  (Some
 	// block devices don't do BLKGETSIZE right.)

 	do {
 		char temp;

 		pos = bottom + (top - bottom) / 2;

 		// If we can read from the current location, it's bigger.

 		if (lseek(fd, pos, SEEK_SET)>=0 && safe_read(fd, &temp, 1)==1) {
 			if (bottom == top) bottom = top = (top+1) * 2;
 			else bottom = pos;

 		// If we can't, it's smaller.
 		} else {
 			if (bottom == top) {
 				if (!top) return 0;
 				bottom = top/2;
 			}
 			else top = pos;
 		}
 	} while (bottom + 1 != top);

 	return pos + 1;
 }
 #endif

 int FAST_FUNC bb_putchar_stderr(char ch)
 {
 	return write(STDERR_FILENO, &ch, 1);
 }

 ssize_t FAST_FUNC full_write1_str(const char *str)
 {
 	return full_write(STDOUT_FILENO, str, strlen(str));
 }

 ssize_t FAST_FUNC full_write2_str(const char *str)
 {
 	return full_write(STDERR_FILENO, str, strlen(str));
 }

 static int wh_helper(int value, int def_val, const char *env_name, int *err)
 {
 	/* Envvars override even if "value" from ioctl is valid (>0).
 	 * Rationale: it's impossible to guess what user wants.
 	 * For example: "man CMD | ...": should "man" format output
 	 * to stdout's width? stdin's width? /dev/tty's width? 80 chars?
 	 * We _cant_ know it. If "..." saves text for e.g. email,
 	 * then it's probably 80 chars.
 	 * If "..." is, say, "grep -v DISCARD | $PAGER", then user
 	 * would prefer his tty's width to be used!
 	 *
 	 * Since we don't know, at least allow user to do this:
 	 * "COLUMNS=80 man CMD | ..."
 	 */
 	char *s = getenv(env_name);
 	if (s) {
 		value = atoi(s);
 		/* If LINES/COLUMNS are set, pretend that there is
 		 * no error getting w/h, this prevents some ugly
 		 * cursor tricks by our callers */
 		*err = 0;
 	}

 	if (value <= 1 || value >= 30000)
 		value = def_val;
 	return value;
 }

 /* It is perfectly ok to pass in a NULL for either width or for
  * height, in which case that value will not be set.  */
 int FAST_FUNC get_terminal_width_height(int fd, unsigned *width, unsigned *height)
 {
 	struct winsize win;
 	int err;
 	int close_me = -1;

 	if (fd == -1) {
 		if (isatty(STDOUT_FILENO))
 			fd = STDOUT_FILENO;
 		else
 		if (isatty(STDERR_FILENO))
 			fd = STDERR_FILENO;
 		else
 		if (isatty(STDIN_FILENO))
 			fd = STDIN_FILENO;
 		else
 			close_me = fd = open("/dev/tty", O_RDONLY);
 	}

 	win.ws_row = 0;
 	win.ws_col = 0;
 	/* I've seen ioctl returning 0, but row/col is (still?) 0.
 	 * We treat that as an error too.  */
 	err = ioctl(fd, TIOCGWINSZ, &win) != 0 || win.ws_row == 0;
 	if (height)
 		*height = wh_helper(win.ws_row, 24, "LINES", &err);
 	if (width)
 		*width = wh_helper(win.ws_col, 80, "COLUMNS", &err);

 	if (close_me >= 0)
 		close(close_me);

 	return err;
 }
 int FAST_FUNC get_terminal_width(int fd)
 {
 	unsigned width;
 	get_terminal_width_height(fd, &width, NULL);
 	return width;
 }

 int FAST_FUNC tcsetattr_stdin_TCSANOW(const struct termios *tp)
 {
 	return tcsetattr(STDIN_FILENO, TCSANOW, tp);
 }

 int FAST_FUNC get_termios_and_make_raw(int fd, struct termios *newterm, struct termios *oldterm, int flags)
 {
 //TODO: slattach, shell read might be adapted to use this too: grep for "tcsetattr", "[VTIME] = 0"
 	int r;

 	memset(oldterm, 0, sizeof(*oldterm)); /* paranoia */
 	r = tcgetattr(fd, oldterm);
 	*newterm = *oldterm;

 	/* Turn off buffered input (ICANON)
 	 * Turn off echoing (ECHO)
 	 * and separate echoing of newline (ECHONL, normally off anyway)
 	 */
 	newterm->c_lflag &= ~(ICANON | ECHO | ECHONL);
 	if (flags & TERMIOS_CLEAR_ISIG) {
 		/* dont recognize INT/QUIT/SUSP chars */
 		newterm->c_lflag &= ~ISIG;
 	}
 	/* reads will block only if < 1 char is available */
 	newterm->c_cc[VMIN] = 1;
 	/* no timeout (reads block forever) */
 	newterm->c_cc[VTIME] = 0;
 	if (flags & TERMIOS_RAW_CRNL) {
 /* IXON, IXOFF, and IXANY:
  * IXOFF=1: sw flow control is enabled on input queue:
  * tty transmits a STOP char when input queue is close to full
  * and transmits a START char when input queue is nearly empty.
  * IXON=1: sw flow control is enabled on output queue:
  * tty will stop sending if STOP char is received,
  * and resume sending if START is received, or if any char
  * is received and IXANY=1.
  */
 		/* IXON=0: XON/XOFF chars are treated as normal chars (why we do this?) */
 		/* dont convert CR to NL on input */
 		newterm->c_iflag &= ~(IXON | ICRNL);
 		/* dont convert NL to CR+NL on output */
 		newterm->c_oflag &= ~(ONLCR);
 		/* Maybe clear more c_oflag bits? usually, only OPOST and ONLCR are set.
 		 * OPOST  Enable implementation-defined output processing (is this reqd for all other bits to work?)
 		 * OLCUC  Map lowercase characters to uppercase on output.
 		 * OCRNL  Map CR to NL on output.
 		 * ONOCR  Don't output CR at column 0.
 		 * ONLRET Don't output CR.
 		 */
 	}
 	if (flags & TERMIOS_RAW_INPUT) {
 		/* IXOFF=0: disable sending XON/XOFF if input buf is full */
 		/* IXON=0: XON/XOFF chars are treated as normal chars */
 		/* dont convert anything on input */
 		newterm->c_iflag &= ~(IXOFF|IXON|IXANY|BRKINT|INLCR|ICRNL|IUCLC|IMAXBEL);
 	}
 	return r;
 }

 int FAST_FUNC set_termios_to_raw(int fd, struct termios *oldterm, int flags)
 {
 	struct termios newterm;

 	get_termios_and_make_raw(fd, &newterm, oldterm, flags);
 	return tcsetattr(fd, TCSANOW, &newterm);
 }

 pid_t FAST_FUNC safe_waitpid(pid_t pid, int *wstat, int options)
 {
 	pid_t r;

 	do
 		r = waitpid(pid, wstat, options);
 	while ((r == -1) && (errno == EINTR));
 	return r;
 }

 pid_t FAST_FUNC wait_any_nohang(int *wstat)
 {
 	return safe_waitpid(-1, wstat, WNOHANG);
 }

 // Wait for the specified child PID to exit, returning child's error return.
 int FAST_FUNC wait4pid(pid_t pid)
 {
 	int status;

 	if (pid <= 0) {
 		/*errno = ECHILD; -- wrong. */
 		/* we expect errno to be already set from failed [v]fork/exec */
 		return -1;
 	}
 	if (safe_waitpid(pid, &status, 0) == -1)
 		return -1;
 	if (WIFEXITED(status))
 		return WEXITSTATUS(status);
 	if (WIFSIGNALED(status))
 		return WTERMSIG(status) + 0x180;
 	return 0;
 }

 // Useful when we do know that pid is valid, and we just want to wait
 // for it to exit. Not existing pid is fatal. waitpid() status is not returned.
 int FAST_FUNC wait_for_exitstatus(pid_t pid)
 {
 	int exit_status, n;

 	n = safe_waitpid(pid, &exit_status, 0);
 	if (n < 0)
 		bb_perror_msg_and_die("waitpid");
 	return exit_status;
 }
	/* vi: set sw=4 ts=4: */
	/*
	* Utility routines.
	*
	* Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
	* Copyright (C) 2006 Rob Landley
	* Copyright (C) 2006 Denys Vlasenko
	*
	* Licensed under GPLv2, see file LICENSE in this source tree.
	*/

	/* We need to have separate xfuncs.c and xfuncs_printf.c because
	* with current linkers, even with section garbage collection,
	* if *.o module references any of XXXprintf functions, you pull in
	* entire printf machinery. Even if you do not use the function
	* which uses XXXprintf.
	*
	* xfuncs.c contains functions (not necessarily xfuncs)
	* which do not pull in printf, directly or indirectly.
	* xfunc_printf.c contains those which do.
	*
	* TODO: move xmalloc() and xatonum() here.
	*/

	#include "libbb.h"

	/* Turn on nonblocking I/O on a fd */
	int FAST_FUNC ndelay_on(int fd)
	{
	int flags = fcntl(fd, F_GETFL);
	if (flags & O_NONBLOCK)
	return flags;
	fcntl(fd, F_SETFL, flags \| O_NONBLOCK);
	return flags;
	}

	int FAST_FUNC ndelay_off(int fd)
	{
	int flags = fcntl(fd, F_GETFL);
	if (!(flags & O_NONBLOCK))
	return flags;
	fcntl(fd, F_SETFL, flags & ~O_NONBLOCK);
	return flags;
	}

	void FAST_FUNC close_on_exec_on(int fd)
	{
	fcntl(fd, F_SETFD, FD_CLOEXEC);
	}

	char* FAST_FUNC strncpy_IFNAMSIZ(char dst, const char src)
	{
	#ifndef IFNAMSIZ
	enum { IFNAMSIZ = 16 };
	#endif
	return strncpy(dst, src, IFNAMSIZ);
	}


	/* Convert unsigned integer to ascii, writing into supplied buffer.
	* A truncated result contains the first few digits of the result ala strncpy.
	* Returns a pointer past last generated digit, does _not_ store NUL.
	*/
	void BUG_sizeof(void);
	char* FAST_FUNC utoa_to_buf(unsigned n, char *buf, unsigned buflen)
	{
	unsigned i, out, res;

	if (buflen) {
	out = 0;
	if (sizeof(n) == 4)
	// 2^32-1 = 4294967295
	i = 1000000000;
	#if UINT_MAX > 4294967295 /* prevents warning about "const too large" */
	else
	if (sizeof(n) == 8)
	// 2^64-1 = 18446744073709551615
	i = 10000000000000000000;
	#endif
	else
	BUG_sizeof();
	for (; i; i /= 10) {
	res = n / i;
	n = n % i;
	if (res \|\| out \|\| i == 1) {
	if (--buflen == 0)
	break;
	out++;
	*buf++ = '0' + res;
	}
	}
	}
	return buf;
	}

	/* Convert signed integer to ascii, like utoa_to_buf() */
	char* FAST_FUNC itoa_to_buf(int n, char *buf, unsigned buflen)
	{
	if (!buflen)
	return buf;
	if (n < 0) {
	n = -n;
	*buf++ = '-';
	buflen--;
	}
	return utoa_to_buf((unsigned)n, buf, buflen);
	}

	// The following two functions use a static buffer, so calling either one a
	// second time will overwrite previous results.
	//
	// The largest 32 bit integer is -2 billion plus NUL, or 1+10+1=12 bytes.
	// It so happens that sizeof(int) * 3 is enough for 32+ bit ints.
	// (sizeof(int) * 3 + 2 is correct for any width, even 8-bit)

	static char local_buf[sizeof(int) * 3];

	/* Convert unsigned integer to ascii using a static buffer (returned). */
	char* FAST_FUNC utoa(unsigned n)
	{
	*(utoa_to_buf(n, local_buf, sizeof(local_buf) - 1)) = '\0';

	return local_buf;
	}

	/* Convert signed integer to ascii using a static buffer (returned). */
	char* FAST_FUNC itoa(int n)
	{
	*(itoa_to_buf(n, local_buf, sizeof(local_buf) - 1)) = '\0';

	return local_buf;
	}

	/* Emit a string of hex representation of bytes */
	char* FAST_FUNC bin2hex(char p, const char cp, int count)
	{
	while (count) {
	unsigned char c = *cp++;
	/* put lowercase hex digits */
	*p++ = 0x20 \| bb_hexdigits_upcase[c >> 4];
	*p++ = 0x20 \| bb_hexdigits_upcase[c & 0xf];
	count--;
	}
	return p;
	}

	/* Convert "[x]x[:][x]x[:][x]x[:][x]x" hex string to binary, no more than COUNT bytes */
	char* FAST_FUNC hex2bin(char dst, const char str, int count)
	{
	errno = EINVAL;
	while (*str && count) {
	uint8_t val;
	uint8_t c = *str++;
	if (isdigit(c))
	val = c - '0';
	else if ((c\|0x20) >= 'a' && (c\|0x20) <= 'f')
	val = (c\|0x20) - ('a' - 10);
	else
	return NULL;
	val <<= 4;
	c = *str;
	if (isdigit(c))
	val \|= c - '0';
	else if ((c\|0x20) >= 'a' && (c\|0x20) <= 'f')
	val \|= (c\|0x20) - ('a' - 10);
	else if (c == ':' \|\| c == '\0')
	val >>= 4;
	else
	return NULL;

	*dst++ = val;
	if (c != '\0')
	str++;
	if (*str == ':')
	str++;
	count--;
	}
	errno = (*str ? ERANGE : 0);
	return dst;
	}

	/* Return how long the file at fd is, if there's any way to determine it. */
	#ifdef UNUSED
	off_t FAST_FUNC fdlength(int fd)
	{
	off_t bottom = 0, top = 0, pos;
	long size;

	// If the ioctl works for this, return it.

	if (ioctl(fd, BLKGETSIZE, &size) >= 0) return size*512;

	// FIXME: explain why lseek(SEEK_END) is not used here!

	// If not, do a binary search for the last location we can read. (Some
	// block devices don't do BLKGETSIZE right.)

	do {
	char temp;

	pos = bottom + (top - bottom) / 2;

	// If we can read from the current location, it's bigger.

	if (lseek(fd, pos, SEEK_SET)>=0 && safe_read(fd, &temp, 1)==1) {
	if (bottom == top) bottom = top = (top+1) * 2;
	else bottom = pos;

	// If we can't, it's smaller.
	} else {
	if (bottom == top) {
	if (!top) return 0;
	bottom = top/2;
	}
	else top = pos;
	}
	} while (bottom + 1 != top);

	return pos + 1;
	}
	#endif

	int FAST_FUNC bb_putchar_stderr(char ch)
	{
	return write(STDERR_FILENO, &ch, 1);
	}

	ssize_t FAST_FUNC full_write1_str(const char *str)
	{
	return full_write(STDOUT_FILENO, str, strlen(str));
	}

	ssize_t FAST_FUNC full_write2_str(const char *str)
	{
	return full_write(STDERR_FILENO, str, strlen(str));
	}

	static int wh_helper(int value, int def_val, const char env_name, int err)
	{
	/* Envvars override even if "value" from ioctl is valid (>0).
	* Rationale: it's impossible to guess what user wants.
	* For example: "man CMD \| ...": should "man" format output
	* to stdout's width? stdin's width? /dev/tty's width? 80 chars?
	* We _cant_ know it. If "..." saves text for e.g. email,
	* then it's probably 80 chars.
	* If "..." is, say, "grep -v DISCARD \| $PAGER", then user
	* would prefer his tty's width to be used!
	*
	* Since we don't know, at least allow user to do this:
	* "COLUMNS=80 man CMD \| ..."
	*/
	char *s = getenv(env_name);
	if (s) {
	value = atoi(s);
	/* If LINES/COLUMNS are set, pretend that there is
	* no error getting w/h, this prevents some ugly
	* cursor tricks by our callers */
	*err = 0;
	}

	if (value <= 1 \|\| value >= 30000)
	value = def_val;
	return value;
	}

	/* It is perfectly ok to pass in a NULL for either width or for
	* height, in which case that value will not be set. */
	int FAST_FUNC get_terminal_width_height(int fd, unsigned width, unsigned height)
	{
	struct winsize win;
	int err;
	int close_me = -1;

	if (fd == -1) {
	if (isatty(STDOUT_FILENO))
	fd = STDOUT_FILENO;
	else
	if (isatty(STDERR_FILENO))
	fd = STDERR_FILENO;
	else
	if (isatty(STDIN_FILENO))
	fd = STDIN_FILENO;
	else
	close_me = fd = open("/dev/tty", O_RDONLY);
	}

	win.ws_row = 0;
	win.ws_col = 0;
	/* I've seen ioctl returning 0, but row/col is (still?) 0.
	* We treat that as an error too. */
	err = ioctl(fd, TIOCGWINSZ, &win) != 0 \|\| win.ws_row == 0;
	if (height)
	*height = wh_helper(win.ws_row, 24, "LINES", &err);
	if (width)
	*width = wh_helper(win.ws_col, 80, "COLUMNS", &err);

	if (close_me >= 0)
	close(close_me);

	return err;
	}
	int FAST_FUNC get_terminal_width(int fd)
	{
	unsigned width;
	get_terminal_width_height(fd, &width, NULL);
	return width;
	}

	int FAST_FUNC tcsetattr_stdin_TCSANOW(const struct termios *tp)
	{
	return tcsetattr(STDIN_FILENO, TCSANOW, tp);
	}

	int FAST_FUNC get_termios_and_make_raw(int fd, struct termios newterm, struct termios oldterm, int flags)
	{
	//TODO: slattach, shell read might be adapted to use this too: grep for "tcsetattr", "[VTIME] = 0"
	int r;

	memset(oldterm, 0, sizeof(oldterm)); / paranoia */
	r = tcgetattr(fd, oldterm);
	newterm = oldterm;

	/* Turn off buffered input (ICANON)
	* Turn off echoing (ECHO)
	* and separate echoing of newline (ECHONL, normally off anyway)
	*/
	newterm->c_lflag &= ~(ICANON \| ECHO \| ECHONL);
	if (flags & TERMIOS_CLEAR_ISIG) {
	/* dont recognize INT/QUIT/SUSP chars */
	newterm->c_lflag &= ~ISIG;
	}
	/* reads will block only if < 1 char is available */
	newterm->c_cc[VMIN] = 1;
	/* no timeout (reads block forever) */
	newterm->c_cc[VTIME] = 0;
	if (flags & TERMIOS_RAW_CRNL) {
	/* IXON, IXOFF, and IXANY:
	* IXOFF=1: sw flow control is enabled on input queue:
	* tty transmits a STOP char when input queue is close to full
	* and transmits a START char when input queue is nearly empty.
	* IXON=1: sw flow control is enabled on output queue:
	* tty will stop sending if STOP char is received,
	* and resume sending if START is received, or if any char
	* is received and IXANY=1.
	*/
	/* IXON=0: XON/XOFF chars are treated as normal chars (why we do this?) */
	/* dont convert CR to NL on input */
	newterm->c_iflag &= ~(IXON \| ICRNL);
	/* dont convert NL to CR+NL on output */
	newterm->c_oflag &= ~(ONLCR);
	/* Maybe clear more c_oflag bits? usually, only OPOST and ONLCR are set.
	* OPOST Enable implementation-defined output processing (is this reqd for all other bits to work?)
	* OLCUC Map lowercase characters to uppercase on output.
	* OCRNL Map CR to NL on output.
	* ONOCR Don't output CR at column 0.
	* ONLRET Don't output CR.
	*/
	}
	if (flags & TERMIOS_RAW_INPUT) {
	/* IXOFF=0: disable sending XON/XOFF if input buf is full */
	/* IXON=0: XON/XOFF chars are treated as normal chars */
	/* dont convert anything on input */
	newterm->c_iflag &= ~(IXOFF\|IXON\|IXANY\|BRKINT\|INLCR\|ICRNL\|IUCLC\|IMAXBEL);
	}
	return r;
	}

	int FAST_FUNC set_termios_to_raw(int fd, struct termios *oldterm, int flags)
	{
	struct termios newterm;

	get_termios_and_make_raw(fd, &newterm, oldterm, flags);
	return tcsetattr(fd, TCSANOW, &newterm);
	}

	pid_t FAST_FUNC safe_waitpid(pid_t pid, int *wstat, int options)
	{
	pid_t r;

	do
	r = waitpid(pid, wstat, options);
	while ((r == -1) && (errno == EINTR));
	return r;
	}

	pid_t FAST_FUNC wait_any_nohang(int *wstat)
	{
	return safe_waitpid(-1, wstat, WNOHANG);
	}

	// Wait for the specified child PID to exit, returning child's error return.
	int FAST_FUNC wait4pid(pid_t pid)
	{
	int status;

	if (pid <= 0) {
	/errno = ECHILD; -- wrong. /
	/* we expect errno to be already set from failed [v]fork/exec */
	return -1;
	}
	if (safe_waitpid(pid, &status, 0) == -1)
	return -1;
	if (WIFEXITED(status))
	return WEXITSTATUS(status);
	if (WIFSIGNALED(status))
	return WTERMSIG(status) + 0x180;
	return 0;
	}

	// Useful when we do know that pid is valid, and we just want to wait
	// for it to exit. Not existing pid is fatal. waitpid() status is not returned.
	int FAST_FUNC wait_for_exitstatus(pid_t pid)
	{
	int exit_status, n;

	n = safe_waitpid(pid, &exit_status, 0);
	if (n < 0)
	bb_perror_msg_and_die("waitpid");
	return exit_status;
	}