so this is supposedly not a difficult question, but I've been getting this problem a few times when running my code in VS code. I am trying to separate the alphabets and numbers from the string, and I have used the method as follows (in my code) according to what is taught in the book. However, despite having the program running, the output is wrong.
Here is my code:
#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <string.h>
int main(){
int weight = 0;
int height = 0;
char wunit[] = "";
char hunit[] = "";
printf("Enter the body weight: ");
scanf("%d%s",&weight,wunit);
printf("Enter the height: ");
scanf("%d%s",&height,hunit);
printf("%d,%s,%d,%s", weight, wunit, height, hunit);
return 0;
}
The thing is,if I type in 20lb for weight, and 30mt for height, what happens is that it gives the output: 20,t,30,mt; which generates this weird âtâ instead of lb, and I have no idea why this is the case.
Similarly, when I type 30kg for weight, and 20cm for height. It generates this weird output:30,m,0, cm. The kg becomes a 'm' and the 20 is now a '0'!? Why is that the case? The expected output would be 30,kg,20,cm
I tried simply replacing the strings, but that doesn't solve the problem fundamentally. For instance, (considering when my user puts logical inputs like lb or kg for weight), I tried this substitution and it appears to work, but doesn't fix the issue of making 20 -> 0
#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <string.h>
int main(){
int weight = 0;
int height= 0;
char wunit[] = "";
char hunit[] = "";
char wunit2[] = "lb";
char dummy[] = "t";
printf("Enter the body weight: ");
scanf("%d%s",&weight,wunit);
printf("Enter the height: ");
scanf("%d%s",&height,hunit);
if (strcmp(wunit,dummy)==0){
printf("%d,%s,%d,%s\n", weight, wunit2, height, hunit);
}
//printf("%d,%s,%d,%s", weight, wunit, height, hunit);
return 0;
}
I've also tried running it in codecollab, and it shows this error of "stack smashing detected" after I run it a few times, which got me more confused, what has it to do with this?
Thanks in advance.
wunit is an array of size 1 (it is initialized to "", which in chars looks like {'\0'}). What happens when you try to put lots of characters (say, "lb", which is {'l', 'b', '\0'}) into a memory location that is smaller than it should be?
scanf happily writes as many bytes as needed, smashing anything in its way ("stack-smashing", because wunit and all those local variables are stored on the stack). Try to give scanf more space, say using
char wunit[10] = "";
And never ever use "%s" directly. Limit the maximum of characters that you will allow scanf to place, for example using "%9s" to ensure that at most 9 characters + terminator (10 total) will be read.
This works for me:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(){
int weight = 0;
int height = 0;
char wunit[10] = "";
char hunit[10] = "";
printf("Enter the body weight: ");
scanf("%d%9s",&weight,wunit);
printf("Enter the height: ");
scanf("%d%9s",&height,hunit);
printf("%d,%s,%d,%s", weight, wunit, height, hunit);
return 0;
}
Note: scanf with %s is rightfully considered very dangerous. See https://stackoverflow.com/a/2430310/15472
I'm currently doing the CS50 Harvard Course and I'm stuck in problem set 2.
I made this program that takes a name and prints the initials, it takes the name in the command line. How can I use get_string() instead of argv, and argc wich is very unorthodox and sloppy, so I can prompt the user to give me her/his name. Thank you.
#include <cs50.h>
#include <ctype.h>
#include <stdio.h>
#include <string.h>
int main(int argc, string argv[])
{
//How do I use Get_string() so I don't have to use argv and argc??
//iterate over strings on the vector (words)
for (int i = 0; i < argc; i++)
{
//prints the 0 character of each string, use "toupper" to convert into capital letters
printf("%c", toupper(argv[i][0]));
}
printf("\n");
}
use Array,
let's say for 10 names
string name[10];
for (int i = 0; i < 10; i++)
{
name[i] = get_string("Enter your name: /n");
}
I am new to coding and I keep getting stuck in the first few lines of code and I cannot figure out why. This is what I have so far:
#include <stdio.h>
#include <cs50.h>
int main(void);
int n;
{
printf("Minute: ");
int n = get_int();
}
I am getting this message when I try to compile the code:
What did I do wrong?
You're trying to call the main function. You should only define it. It will be called when the program is executed (it is the "entry point").
To define it, remove the semicolon after
int main(void)
You can also remove that void keyword
Then move that line down, between
int n; and the { that comes after it
Additionally, you're declaring the n variable twice. After you fix the first error, the compiler will complain about this one. Remove one of the declarations then.
You should remove the semicolon after int main(void) and move the variable declaration for n within the braces. Here is the correct code below.
#include <stdio.h>
#include <cs50.h>
int main(void)
{
int n;
printf("Minute: ");
int n = get_int();
}
I compile this code in Ubuntu. I did it more than 10 times but I got only AAA BBB CCC . I believe sequence can be changed but I don't know why. Please somebody kindly tell me the reason.
#include <stdio.h>
#include <pthread.h>
#include <sched.h>
#include <unistd.h>
void *thread_entry(void *ptr)
{
char *name = (char *)ptr;
printf("%s-A\n", name);
sleep(1); //sched_yield();
printf("%s-B\n", name);
sleep(1); //sched_yield();
printf("%s-C\n", name);
}
int main()
{
#define MAX_THREAD 3
pthread_t thread[MAX_THREAD];
char *thread_name[MAX_THREAD] = {"thread1", "thread2", "thread3"};
int i;
for (i = 0; i < MAX_THREAD; i++)
pthread_create(&thread[i], NULL, thread_entry, thread_name[i]);
for (i = 0; i < MAX_THREAD; i++)
pthread_join(thread[i], NULL);
return 0;
}
Theoretically it's possible, but it's very unlikely you would see another ordering.
You spawn 3 threads, then one of them prints "A" and waits for 1 second until it will print "B". One second of sleeping is far more than enough for the rest threads to print "A". Same for "B" and "C".
Why output of ls executed here is not colored?
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <pty.h>
#include <sys/wait.h>
int main(int argc, char **argv ) {
termios termp; winsize winp;
int amaster; char name[128];
if (forkpty(&amaster, name, &termp, &winp) == 0) {
system("ls"); // "ls --color" will work here!
return 0;
}
wait(0);
char buf[128]; int size;
while (1) {
size = read(amaster, buf, 127);
if (size <= 0) break;
buf[size] = 0;
printf("%s", buf);
}
return 0;
}
According to man (and ls.c that I am inspecting) it should be colored if isatty() returns true. After forkpty() it must be true. Besides, ls DOES output in columnized mode in this example! Which means it feels it has tty as output.
Of course I do not want only ls to output color, but an arbitrary program to feel that it has real color enabled tty behind.
I just wrote a simple test:
#include <unistd.h>
int main() {
printf("%i%i%i%i%i\n", isatty(0), isatty(1), isatty(2), isatty(3), isatty(4));
}
and call it in a child part of forkpty, and it displays 11100, which means ls should be colored!
OK, as it seems the fact that ls produces no color output has nothing to do with forkpty(). It is just not color enabled by default. But now, maybe that's another question, why it is not color if it just checks isatty()?