Thread: simple string program

hey there,
i have a very trivial program which is given a text file as a parameter, and basically has to print any of the characters in the file which are characters (i.e. not numbers etc) to the screen.

i am using the isprint() method, which should return true only if the passed integer is of type char or space.

the program, at current, returns everything -regardless of whether it is character or int. if anyone could please tell me where i have made my error i would be greaty appreciative.

thanks in advance, twans

Code:

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

char *read_text(char *);
int encode(char *);
int decode(char *);

int main(int argc, char **argv) {
	char *text;

	if (argc != 2) {
		printf("USAGE: %s filename\n", argv[0]);
		exit(1);
	}

	text=read_text(argv[1]);
	
	printf("Characters and Strings:\n");

	isString(text);
	printf("%s\n", text);

	free(text);	
	return 0;
}



char *read_text(char *filename) {
	FILE 		*filedes;
	static char	*text;
	int			file_len, 
				i;

	if(!(filedes = fopen(filename, "r"))) {
		perror("fopen()");	
		exit(2);
	}



	/* One quick way to find out a file's size... */
	fseek(filedes, 0L, SEEK_END);
	file_len = ftell(filedes);
	rewind(filedes);

#ifdef DEBUG
	printf("File: %s; Length: %d\n", filename, file_len);
#endif

	if(!(text = (char *)malloc((size_t) (file_len + 1)))) {
		perror("malloc()");
		exit(3);
	}

	for(i = 0; i < file_len; i++) 
		text[i] = fgetc(filedes);		
	text[file_len] = (char)NULL;						/* NULL-terminate the character array */

#ifdef DEBUG
	for(i = 0; i <= file_len; i++)
		if (text[i] == (char)NULL)
			printf("NULL\n");
		else
			fputc(text[i], stdout);
	exit(0);
#endif

	fclose(filedes);
	return text;
}

int isString(char *tempText)
{
	int x;
	while((x = *tempText) != '\0')
	{
		if(isprint(x))
			{
			*(tempText) = (char) x ;
			}
		*(tempText++);
	}
	return 0;
}

hi salem, thanks for your reply. if you look at my isString method, however, it will always return 0. i was trying to use a pointer to the 'text' variable to modify it as required. therefore your 'if' solution is not applicable without modifying the structure of the function.

.. i think in the isString function itself i am overlooking something, maybe with the pointer?

Code:

int isString(char *tempText)
{
	int x;
	while((x = *tempText) != '\0')
	{
		if(isprint(x))
			{
			*(tempText) = (char) x ;
			}
		else { *(tempText) = ' '; }
		*(tempText++);
	}
	return 0;
}

I was just going to mention that the isString function always returns zero, twans, but you beat me to it...

How can the isString function do anything for you if it always returns zero? Or can the function manipulate the values passed to it because of the pointers?