c_handle_var_argv.c

/*

Modify the pattern finding program to take its input from a set of named files
or, if no files are named as arguments, from the standard input. Should the
file name be printed when a matching line is found?

*/

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#define MAXLINE 1000

int get_line(FILE *fp, char *s, int lim);
int get_line(FILE *fp, char *s, int lim)
{
	int c = 0;
	int i;
	for (i = 0; i < lim - 1 && (c = fgetc(fp)) != EOF && c != '\n'; ++i)
		*s++ = (char) c;
	if (c == '\n') {
		*s++ = (char) c;
		++i;
	}
	*s = '\0';
	return i;
}

static int except = 0;
static int number = 0;
static int found = 0;

void find_in(char *filename, char *pattern, FILE *fp);
void find_in(char *filename, char *pattern, FILE *fp)
{
	char line[MAXLINE];
	long lineno = 0;
	while (get_line(fp, line, MAXLINE) > 0) {
		lineno++;
		if ((strstr(line, pattern) != NULL) != except) {
			if (filename != NULL)
				printf("%s:", filename);
			if (number)
				printf("%ld:", lineno);
			printf("%s", line);
			found++;
		}
	}
}

int main(int argc, char *argv[])
{
	int c;
	char *progname = argv[0];
	while (--argc > 0 && (*++argv)[0] == '-')
		while ((c = *++argv[0]))
			switch(c) {
				case 'x':
					except = 1;
					break;
				case 'n':
					number = 1;
					break;
				default:
					printf("find: illegal option %c\n", c);
					argc = 0;
					found = -1;
					break;
			}

	if (*argv == NULL)
		printf("Usage: find -x -n pattern [FILE]+\n");
	else {
		char *pattern = *argv;

		int given_files = 0;
		while (*++argv) {
			given_files = 1;
			char *filename = *argv;
			FILE *fp = fopen(filename, "r");
			if (fp == NULL) {
				fprintf(stderr, "%s: can't open file %s\n", progname, filename);
				exit(1);
			}
			find_in(filename, pattern, fp);
		}
		if (!given_files)
			find_in(NULL, pattern, stdin);
	}
	return found;
}