Help is needed to read text from a file

Hi all:

I have been given a text file full of text pattern as shown below:


# VIEW OBJFILE = iiomsview16.V

VIEW II_STD_HEADER_T

# TYPE CNAME FBNAME COUNT FLAG SIZE NULL VALUE
# ----- -------- --------- ----- ---- ---- ----------

string hd_cd1 HEADER_CD 1 - 13 " "
string hd_text HEADER_TEXT 1 - 41 " "


I need to read this text file content and put into a customized ADT. One of the rules while reading from this file is that when a line started with a '#' character, the line is treated as comment and ignored.

My plan is:
Using fgetc() function to read in the characters from the file one by one;

My question is:
How do I detect end of a line or a "tab" character or the end of the file? They are NOT written in the ASNII chart, I think.

Can anyone help me please?

Thank you

Quote:

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Originally Posted by yuzhangoscar

Hi all:

I have been given a text file full of text pattern as shown below:


# VIEW OBJFILE = iiomsview16.V

VIEW II_STD_HEADER_T

# TYPE CNAME FBNAME COUNT FLAG SIZE NULL VALUE
# ----- -------- --------- ----- ---- ---- ----------

string hd_cd1 HEADER_CD 1 - 13 " "
string hd_text HEADER_TEXT 1 - 41 " "


I need to read this text file content and put into a customized ADT. One of the rules while reading from this file is that when a line started with a '#' character, the line is treated as comment and ignored.

My plan is:
Using fgetc() function to read in the characters from the file one by one;

My question is:
How do I detect end of a line or a "tab" character or the end of the file? They are NOT written in the ASNII chart, I think.

Can anyone help me please?

Thank you

---

The end of line is the '\n' character, the tab is the '\t' character and the end of file the EOF character. Test for those characters.
You can also look up fgets() that reads a whole line. Or other functions.
So if you want end of file you just do for example buffer[i] == EOF, newline buffer[i] == '\n'

Quote:

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end of file the EOF character

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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);
}

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

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

Code:

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                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:

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if (chr != '#' ) break;

---

The loop will continue anyways.

--
Mats

Quote:

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Originally Posted by matsp

Huh?
Why not just do:

Code:

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

---

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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?

Quote:

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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?

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

Code:

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else if (chr == 0) break;

---

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

Quote:

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the null terminator, the end of the line

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

But what is missing - check for EOF condition

Quote:

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Originally Posted by MK27

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

Code:

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else if (chr == 0) break;

---

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

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

Quote:

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Originally Posted by vart

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

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

Quote:

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Originally Posted by vart

check for EOF condition

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

Thank you all. I have solved my problem, cheers everyone.

Quote:

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from my post #4:

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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