C-specific code examples

char to int.c

@@ -0,0 +1,4 @@
+	/*char to int (48 is the value of '0' in the ascii table)
+	since casting char to int returns an int with the value of the char inside the ascii table (see ascii table), subtracting 48 makes the new int is correspettive in number.
+
+	printf("%d", ((int) ('3')) - 48);

size of an array.c

@@ -0,0 +1,4 @@
+	int ciao[3];
+
+	printf("%ld", sizeof(ciao) / sizeof(*ciao)); //size in bytes of the array divided by the size in bytes of the type (pointer to the array, or first array of the element)
+

timeout_scanf.c

@@ -0,0 +1,36 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <sys/time.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+int main(void) {
+	int value = 0;
+	struct timeval tmo;
+	fd_set readfds;
+
+	printf("Enter a non-zero number: ");
+	fflush(stdout);
+
+	FD_ZERO(&readfds);
+	FD_SET(0, &readfds);
+	tmo.tv_sec = 3;
+	tmo.tv_usec = 0;
+
+	if (select(1, &readfds, NULL, NULL, &tmo) == 0) {
+		printf("User dont give input");
+		//return (1);
+	} else {
+		scanf("%d", &value);
+		if (value != 0) {
+			printf("User input a number");
+		} else {
+			printf("User dont give input2");
+		}
+	}
+
+	printf("boh");
+
+	return (0);
+}

variable-length-array_aka_vectors_but_in_c.c

@@ -0,0 +1,24 @@
+//This program creates and manages a variable-length array
+
+	 int  length = 1; 																//first length of the array
+	 int* out = (int*) malloc(length * sizeof(int));									//allocates as much ram as indicated by the length of the array (b) multiplied by the size on an int in Ram. This is actually a pointer to the ram that as been allocated
+	 int* out_copy = out; 															//now creates a pointer to a copy of the other pointer, that acts as a constant copy
+
+	 printf("Starting array length:   %d\n\tNew value in index 0 is:   ", length);
+	 out[0] = 32;																	//assign a value to the first element
+	 printf("%d\n", out[0]);															//prints the new value
+
+	 length = 2;																		//now it changes the length
+	 printf("New array length:    %d\n", length);
+	 printf("Creating new array with increased length\n");
+
+	 out = (int*) malloc(length * sizeof(int));										//creates the new array, with the new length
+	 out=out_copy;																	//copies the pointer to the old array into the new one
+
+	 printf("Longer array has been created and old array value copied into the new one\nNew values are:\n");
+
+	 out[1] = 33;																	//adds a variable into the new index that has been created when increasing lenght
+	 printf("\t%d\n", out[0]);															//prints the value in the first index (it is still the value instantiated before)
+	 printf("\t%d\n", out[1]);															//prints the new value: the array length as increased
+
+	 free(out_copy);