command line program example Archives

K and R C, Solution to Exercise 5-10:
K and R C Programs Exercises provides the solution to all the exercises in the C Programming Language (2nd Edition). You can learn and solve K&R C Programs Exercise.
C Program to evaluate reverse Polish expression from the command line, where each operator or operand is a separate argument.
For example:expr 2 3 4 + * evaluates 2 X (3 + 4). Read more about C Programming Language .

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* programs for commercial purposes,
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#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>

#define MAX 1000

double stack[MAX];
int stack_height = 0;

void panic(const char *msg) {
	fprintf(stderr, "%sn", msg);
	exit(EXIT_FAILURE);
}

void push(double value) {
	if (stack_height == MAX)
		panic("stack is too high!");
	stack[stack_height] = value;
	++stack_height;
}

double pop(void) {
	if (stack_height == 0)
		panic("stack is empty!");
	return stack[--stack_height];
}

int main(int argc, char **argv) {
	int i;
	double value;

	for (i = 1; i < argc; ++i) {
		switch (argv[i][0]) {
		case '':
			panic("empty command line argument");
			break;
		case '0':
		case '1':
		case '2':
		case '3':
		case '4':
		case '5':
		case '6':
		case '7':
		case '8':
		case '9':
			push(atof(argv[i]));
			break;
		case '+':
			push(pop() + pop());
			break;
		case '-':
			value = pop();
			push(pop() - value);
			break;
		case '*':
			push(pop() * pop());
			break;
		case '/':
			value = pop();
			push(pop() / value);
			break;
		default:
			panic("unknown operator");
			break;
		}
	}

	printf("%gn", pop());
	return 0;
}

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/***********************************************************
* You can use all the programs on www.c-program-example.com
* for personal and learning purposes. For permissions to use the
* programs for commercial purposes,
* contact [email protected]
* To find more C programs, do visit www.c-program-example.com
* and browse!
*
* Happy Coding
***********************************************************/

#include <stdio.h>

main(int argc, char *argv[]) {
int count;

/* Main takes two variables 'argc' is the number of parms on the
* command line and 'argv' is a pointer to each of the parameters.
*
* int argc -- integer number called 'argc'
* char *argv[] -- Character pointer array!
*/

printf("%i parameters entered on the command line.n", argc);

/*
* progname argc = 1
* progname parm1 parm2 argc = 3
*/

/*
* We take 1 from argc because
* the argv array starts at zero
* an ends at argc -1
*/

for (count = 0; count <= argc - 1; count++) {
/* printf expects a pointer
* to the text
*/

printf("parm %d is %sn", count, argv[count]);
}
}

C Program Examples

command line program example

K & R C Programs Exercise 5-10.

C Program to Demonstrate getting the parameters from the command line.