Command Line Arguments

Program #1: Echo, Version 1

This program echos its command line arguments on a separate line.

/*
 * print arguments followed by a newline
 */
#include <stdio.h> 

int main(int argc, char *argv[])
{
	int i;			/* counter in a for loop */
 
	/*
	 * go through the argument list, skipping arg 0 (it's
	 * the program name)
	 */
	for(i = 1; i < argc-1; i++)
		printf("%s ", argv[i]);
 
	/*
	 * now print the last argument, UNLESS it is arg 0
	 */
	if (argc > 1)
		printf("%s\n", argv[argc-1]);
 
	/*
	 * return success!
	 */
	return(0);
}

Program #2: Echo, Version 2

This also echos its command line arguments, but if the first argument is -n, it suppresses the trailing newline and does not print that argument.

#include <stdio.h>
 
int main(int argc, char *argv[])
{
	int prnl = 1;			/* 1 to print newline, 0 not to */
	int i;				/* counter in a for loop */
 
	/*
	 * if argument 0 is -n, set prnl to suppress newline
	 * skip it in the rinting; otherwise, print beginning with arg 1
	 */
	if (argc > 1 &&
		argv[1][0] == '-' && argv[1][1] == 'n' && argv[1][2] == '\0'){
		prnl = 0;
		i = 2;
	}
	else
		i = 1;
 
	/*
	 * go through the argument list, skipping arg 0 (it's
	 * the program name) and arg 1 if needed
	 */
	for( ; i < argc-1; i++)
		printf("%s ", argv[i]);
 
	/*
	 * now print the last argument, UNLESS it is arg 0, or arg 1 and -n
	 */
	if ((prnl && argc > 1) || (!prnl && argc > 2)){
		printf("%s", argv[argc-1]);
		/* put out the newline */
		if (prnl)
			putchar('\n');
	}
 
	/*
	 * return success!
	 */
	return(0);
}