Thread: Help is needed to read text from a file

end of file the EOF character

actually - EOF is return code of fgetc that indicates read error, this is not a character and this is the reason fgetc returns int so the return values are any character from 0 to 255 AND EOF

Is this illustrative?

Code:

#include <stdio.h>

int main() {
        int chr;
        FILE *fstRO = fopen("/tmp/thefile.txt", "r");
        while ((chr=fgetc(fstRO)) != -1) {
                if (chr == '#') while (1) if (chr=fgetc(fstRO) == '\n') {
                                chr=fgetc(fstRO);
                                if (chr == '#') continue;
                                else break;}
                printf("&#37;c", chr);
        }   
       fclose(fstRO);
}

someone else might help you with the "Abstract Data Type" stuff

ps. in this "EOF" is represented by the "-1" from fgetc

Code:

                if (chr == '#') while (1) if (chr=fgetc(fstRO) == '\n') {
                                chr=fgetc(fstRO);
                                if (chr == '#') continue;
                                else break;}

Huh?
Why not just do:

Code:

if (chr == '#') 
    while(fgect() != '\n')   ; 
else
   putchar(chr);

There is certainly no need to use continue the way you do - just use

Code:

if (chr != '#' ) break;

The loop will continue anyways.

--
Mats

Originally Posted by matsp

Huh?
Why not just do:

Code:

if (chr == '#') 
    while(fgect() != '\n')   ; 
else
   putchar(chr);

Aha -- I tested this BEFORE I posted it. The "if" trap needs to be before the putchar or printf to catch '#', AND it needs to catch the \n from the end of a comment. Your snippet above will 1) print this \n 2) also print a "#" if it starts on a line after a line starting with "#", then (having missed the trap) continue printing the entire comment.

#2 (no pun!) is the reason for the continue, otherwise we should break.

See what I mean?

And what will happen if the last line of the file begins with the # and does not have \n at the end?

Originally Posted by vart

And what will happen if the last line of the file begins with the # and does not have \n at the end?

yep. there should be a line like this after else break;

Code:

else if (chr == 0) break;

ASCII decimal 0 = '\0' (the null terminator, the end of the line)

the null terminator, the end of the line

2 different things
'\0' - C-string terminator
'\n' - line terminator

But what is missing - check for EOF condition

Originally Posted by MK27

yep. there should be a line like this after else break;

Code:

else if (chr == 0) break;

ASCII decimal 0 = '\0' (the null terminator, the end of the line)

Better to just compare chr with '\0'. Makes it clearer, and more portable.

Originally Posted by vart

2 different things
'\0' - C-string terminator
'\n' - line terminator

'\n' is certainly NOT a "line terminator", but nomenclature aside:

Originally Posted by vart

check for EOF condition

from my post #4:
in this "EOF" is represented by the "-1" from fgetc

from my post #4:

you have more when 1 fgetc in the code - only one is checked

EOF could be any other negative value, standard does not require it to be -1