How to end program with period (.) - c

Question

The user entries different characters: uppercase and lowercase letters and numbers. Entering ends with a period (.) The program should then calculate and print sum of all entered numbers, and ignore everything else. Program won't end with a period (.)
#include <stdio.h>
int main() {
int s=0, a;
char n;
printf("Unesite znakove: ");
for ( ; ; ) {
scanf ("%c", &n);
if (n!='.') {
a=(int)n;
if (a>47 && a<58) {
a=a-48;
s+=a;
}
else continue;
}
else {
break;
}
}
printf ("\nSuma je: %d", s);
return 0;
}

Answer 1

stdin is usually line buffered.
Code does not see any input until '\n' is entered. Entering "123." is not enough. Code needs a final Enter: '\n' (or closure of stdin).

Answer 2

the stdin is being input in 'cooked' mode, which means nothing is actually visible to the program until either EOF or is entered by the user.
If you want the data to be available to the program, keystroke by keystroke, then the terminal needs to be in 'raw' mode
the following code demonstrates how to set the terminal into 'raw' mode
Note: code swiped from: http://www.minek.com/files/unix_examples/raw.html
#include <stdio.h>
#include <signal.h>
#include <termios.h>
#include <stdlib.h>
#include <unistd.h>
struct termios oldtermios;
int ttyraw(int fd)
{
/* Set terminal mode as follows:
Noncanonical mode - turn off ICANON.
Turn off signal-generation (ISIG)
including BREAK character (BRKINT).
Turn off any possible preprocessing of input (IEXTEN).
Turn ECHO mode off.
Disable CR-to-NL mapping on input.
Disable input parity detection (INPCK).
Disable stripptcsetattr(fd, TCSAFLUSH, &newtermios)ing of eighth bit on input (ISTRIP).
Disable flow control (IXON).
Use eight bit characters (CS8).
Disable parity checking (PARENB).
Disable any implementation-dependent output processing (OPOST).
One byte at a time input (MIN=1, TIME=0).
*/
struct termios newtermios;
if(tcgetattr(fd, &oldtermios) < 0)
return(-1);
memcpy( newtermios, oldtermios, sizeof(struct termios) );
newtermios.c_lflag &= ~(ECHO | ICANON | IEXTEN | ISIG);
/* OK, why IEXTEN? If IEXTEN is on, the DISCARD character
is recognized and is not passed to the process. This
character causes output to be suspended until another
DISCARD is received. The DSUSP character for job control,
the LNEXT character that removes any special meaning of
the following character, the REPRINT character, and some
others are also in this category.
*/
newtermios.c_iflag &= ~(BRKINT | ICRNL | INPCK | ISTRIP | IXON);
/* If an input character arrives with the wrong parity, then INPCK
is checked. If this flag is set, then IGNPAR is checked
to see if input bytes with parity errors should be ignored.
If it shouldn't be ignored, then PARMRK determines what
character sequence the process will actually see.
When we turn off IXON, the start and stop characters can be read.
*/
newtermios.c_cflag &= ~(CSIZE | PARENB);
/* CSIZE is a mask that determines the number of bits per byte.
PARENB enables parity checking on input and parity generation
on output.
*/
newtermios.c_cflag |= CS8;
/* Set 8 bits per character. */
newtermios.c_oflag &= ~(OPOST);
/* This includes things like expanding tabs to spaces. */
newtermios.c_cc[VMIN] = 1;
newtermios.c_cc[Vtcsetattr(fd, TCSAFLUSH, &newtermios)TIME] = 0;
/* You tell me why TCSAFLUSH. */
if(tcsetattr(fd, TCSAFLUSH, &newtermios) < 0)
return(-1);
return(0);
}
int ttyreset(int fd)
{
if(tcsetattr(fd, TCSAFLUSH, &oldtermios) < 0)
return(-1);
return(0);
}
void sigcatch(int sig)
{
ttyreset(0);
exit(0);
}
void main()
{
int i;
char c;
/* Catch the most popular signals. */
if((int) signal(SIGINT,sigcatch) < 0)
{
perror("signal");
exit(1);
}
if((int)signal(SIGQUIT,sigcatch) < 0)
{
perror("signal");
exit(1);
}
if((int) signal(SIGTERM,sigcatch) < 0)
{
perror("signal");
exit(1);
}
/* Set raw mode on stdin. */
if(ttyraw(0) < 0)
{
fprintf(stderr,"Can't go to raw mode.\n");
exit(1);
}
while( (i = read(0, &c, 1)) == 1)
{
if( (c &= 255) == 0177) /* ASCII DELETE */
break;
printf( "%o\n\r", c);
}
if(ttyreset(0) < 0)
{
fprintf(stderr, "Cannot reset terminal!\n");
exit(-1);
}tcsetattr(fd, TCSAFLUSH, &newtermios)
if( i < 0)
{
fprintf(stderr,"Read error.\n");
exit(-1);
}
exit(0);
}
the main criteria is to declare a struct termios, use tcgetattr(fd, &oldtermios) to acquire the current terminal settings, (for safety, now make a copy of the original terminal settings.) copy oldtermios to a newtermios and modify the newtermios settings for the desired mode, then use tcsetattr(fd, TCSAFLUSH, &newtermios) to modify the terminal to the 'raw' mode.
When done, be sure to call tcsetattr(fd, TCSAFLUSH, &oldtermios); to return the terminal mode to 'cooked'
Note: signal() is obsolete/unreliable, replace with sigaction()