reading text from a file

I don't know where to start, someone please point me in the right direction.

I opened a file in main, sent the file pointer to a function, and am now trying to read in text.


the text file goes something like


5
hello there
ok bye now


5 indicating the number of words. Is there a function to read in words, then when encountering a space, go to the next word? I'm guessing that would make my life too easy.

anyhelp is appreciated thankx.

Quote:

---

Originally Posted by ktran03

I don't know where to start, someone please point me in the right direction.

I opened a file in main, sent the file pointer to a function, and am now trying to read in text.

---

Great, where's what you've got so far?

Quote:

---

the text file goes something like


5
hello there
ok bye now


5 indicating the number of words. Is there a function to read in words, then when encountering a space, go to the next word?

---

No.

Quote:

---

I'm guessing that would make my life too easy.

anyhelp is appreciated thankx.

---

Looks like homework. Show an attempt first. You might use fgetc which reads characters or fgets which reads lines (provided the buffer is big enough).

Try this (untested)

Code:

---

char inputbuffer[200]; //make it big enough to not overflow

while(!fscanf(filepointer,"%s",inputbuffer)) printf("%s\n",inputbuffer);
fclose(filepointer);

---

omfg, after 7 hours of pounding my head....I finally got it to read something in.

Code:

---

    char string[5];
    int i;
   
    for(i=0; i<5; i++){
    string[i] = getc(file);
    printf("%c\n\n", string[i]);
    }

---

the code is very primitive, but atleast I finally got somewhere.

Quote:

---

Originally Posted by cwr

Great, where's what you've got so far?


No.



Looks like homework. Show an attempt first. You might use fgetc which reads characters or fgets which reads lines (provided the buffer is big enough).

---

yo why so bitter?

it is homework. If anyone remembers me from my posts on here, I never ask for code straight. I always ask people to point me in the right direction, so I can learn, and not just get passed code.

Quote:

---

Originally Posted by esbo

Try this (untested)

Code:

---

char inputbuffer[200]; //make it big enough to not overflow

while(!fscanf(filepointer,"%s",inputbuffer)) printf("%s\n",inputbuffer);
fclose(filepointer);

---

---

thankx,

I'm gonna try to implement that.

but what's the difference between fscanf, and getc?

and when I use getc, how do I know I've encountered a white space, and therefore need to move onto a new word in the array?

Quote:

---

Originally Posted by ktran03

Code:

---

    char string[5];
    int i;
   
    for(i=0; i<5; i++){
    string[i] = getc(file);
    printf("%c\n\n", string[i]);
    }

---

---

Okay, so you've managed to create a loop, but it's not much use because it insists on reading exactly 5 characters from the file. What you want is a loop that continues until you read the end of the file or an error. Look up what getc() returns when such a condition is reached, and adjust your loop accordingly.

You're not actually clear on what you need the program to do. What do you intend to do with it aside from read the file?

Quote:

---

Originally Posted by cwr

Okay, so you've managed to create a loop, but it's not much use because it insists on reading exactly 5 characters from the file. What you want is a loop that continues until you read the end of the file or an error. Look up what getc() returns when such a condition is reached, and adjust your loop accordingly.

You're not actually clear on what you need the program to do. What do you intend to do with it aside from read the file?

---

I'm gonna take it one step at a time. The assignment is pretty big, I'm trying not to overwhelm myself, chipping away piece by piece.

but task 1 is to get the words read into a string of characters.

I'm gonna go read up on fscanf a for a bit...

Quote:

---

Originally Posted by ktran03

I'm gonna go read up on fscanf a for a bit...

---

Oops made a bit of an error I should have put

Code:

---

while(fscanf(filepointer,"%s",inputbuffer)!=-1) printf("%s\n",inputbuffer);

---

Not

Code:

---

while(!fscanf(filepointer,"%s",inputbuffer)) printf("%s\n",inputbuffer);

---

This should work, file is called 'all.txt'

Code:

---


#include <stdio.h>


FILE *filepointer;
char inputbuffer[200]; //make it big enough to not overflow

main(){

        if (        (filepointer=fopen("all.txt","r")) == NULL) {
                        puts("all.txt does not exist");
        }
      else{
            while(fscanf(filepointer,"%s",inputbuffer)!=-1) printf("%s\n",inputbuffer);
            fclose(filepointer);
      }
      getchar();
}

---

Quote:

---

Originally Posted by esbo

Try this (untested)

Code:

---

char inputbuffer[200]; //make it big enough to not overflow

while(!fscanf(filepointer,"%s",inputbuffer)) printf("%s\n",inputbuffer);
fclose(filepointer);

---

---

once again you post code with errors.
try to think a little before posting what will you code do if fscanf returns EOF

Quote:

---

Originally Posted by ktran03

thankx,

I'm gonna try to implement that.

but what's the difference between fscanf, and getc?

and when I use getc, how do I know I've encountered a white space, and therefore need to move onto a new word in the array?

---

fscanf reads it's input seperated by white space (unless specified otherwise) according to to the specified format, %s means a character string.

getc reads a character at a time.

Quote:

---

Originally Posted by vart

once again you post code with errors.
try to think a little before posting what will you code do if fscanf returns EOF

---

I was having problems with my code too, I was hoping someone would be able to fix it.
Anyway if it had worked he might have just copied it and not learnt anything.
Think of it as an extended assignment, cwr did say to make an attempt first :)

esbo brings up a good point: what is the length of the longest word that you expect? There are ways to accomodate words of arbitrary length, but that might be a little too complex for you at the moment.

That said, even when you do know the expected maximum length, you should still write code to not overflow your string buffer should invalid input be entered with a word longer than expected.

Modifying esbo's example:

Code:

---

#include <stdio.h>

int main(void) {
    FILE *file_pointer;
    char input_buffer[200];

    if ((file_pointer = fopen("all.txt", "r")) == NULL) {
        puts("all.txt does not exist");
    } else {
        while (fscanf(file_pointer, "%199s", input_buffer) != EOF) {
            printf("%s\n", input_buffer);
        }
        fclose(file_pointer);
    }

    return 0;
}

---

The "%199s" ensures that at most 199 characters will be put in the string, with the last reserved for the terminating null character. Note that with this approach the integer value denoting the number of words will also be read as a word. Perhaps you are supposed to read it first, create a dynamic array of strings with that value as the size, and only then proceed to read in the words into that array?

Quote:

---

Originally Posted by vart

once again you post code with errors.
try to think a little before posting what will you code do if fscanf returns EOF

---

And what did you post which was constructive?

Nothing. Hence - plonk!

Quote:

---

Originally Posted by ktran03

and when I use getc, how do I know I've encountered a white space, and therefore need to move onto a new word in the array?

---

Just by testing for equality with a whitespace character.

if( variable == ' ' ) DoSomething();

Quote:

---

Originally Posted by esbo

And what did you post which was constructive?

Nothing. Hence - plonk!

---

I asked you to think. But I see now that this is not constructive in your case...

Quote:

---

Originally Posted by esbo

And what did you post which was constructive?

---

Some people believe that being condescending is constructive. It's not. :)

You took the time to try work it out and to provide the OP with some code, which gave the OP a solid hint that fscanf was what was required.

You did good, esbo. :)

Quote:

---

Originally Posted by laserlight

esbo brings up a good point: what is the length of the longest word that you expect? There are ways to accomodate words of arbitrary length, but that might be a little too complex for you at the moment.

That said, even when you do know the expected maximum length, you should still write code to not overflow your string buffer should invalid input be entered with a word longer than expected.

Modifying esbo's example:

Code:

---

#include <stdio.h>

int main(void) {
    FILE *file_pointer;
    char input_buffer[200];

    if ((file_pointer = fopen("all.txt", "r")) == NULL) {
        puts("all.txt does not exist");
    } else {
        while (fscanf(file_pointer, "%199s", input_buffer) != EOF) {
            printf("%s\n", input_buffer);
        }
        fclose(file_pointer);
    }

    return 0;
}

---

The "%199s" ensures that at most 199 characters will be put in the string, with the last reserved for the terminating null character. Note that with this approach the integer value denoting the number of words will also be read as a word. Perhaps you are supposed to read it first, create a dynamic array of strings with that value as the size, and only then proceed to read in the words into that array?

---

yes, that's correct. The number of words is given in the txt file.


I've got it dynamically allocate the strings array, but am having trouble copying the temp variable 'buffer' into the array of strings.

when I add these two lines

Code:

---

        strcpy(array[i], buffer);
        printf("%s\n", array[i]);

---

into the while loop reading in the text, I get a segmentation fault.

Quote:

---

Originally Posted by ktran03

when I add these two lines

Code:

---

        strcpy(array[i], buffer);
        printf("%s\n", array[i]);

---

into the while loop reading in the text, I get a segmentation fault.

---

So have you allocated enough space for array[i] before copying over it?

Quote:

---

Originally Posted by vart

So have you allocated enough space for array[i] before copying over it?

---

this is part of it

Code:

---

        array[i] = malloc(sizeof (char) * 20);

---

oh crap, I think i know what's wrong


brb

edit, nm...that can't be it.

I was thinking the first number in the file was being held in buffer, then being strcpy'd.

but since I did a printf statement of the buffer, it skips the number and prints the first word, so

the buffer is holding the first word, not the number.

Code:

---

array[0] = "hellohjhjghjgjhgjhghjgjhgj";
    array[1] = "world";
    printf("%s\n%s\n", array[0], array[1]);

---

i just tested that after the malloc, so it must be big enough

Quote:

---

Originally Posted by ktran03

Code:

---

array[0] = "hellohjhjghjgjhgjhghjgjhgj";
    array[1] = "world";
    printf("%s\n%s\n", array[0], array[1]);

---

i just tested that after the malloc, so it must be big enough

---

got it,

removed these test values and it works. WICKED!!! making progress is wicked.

quick question


how do I know if the file I'm opening is empty?

Quote:

---

Originally Posted by ktran03

quick question


how do I know if the file I'm opening is empty?

---

Why does it matter - if you try to read the file, you will know when you have reached the end. If that is ZERO or 1000 bytes into the file, what difference does it make?

You can measure the length of the file using fseek() and ftell(). But for most things, it doesn't really matter much.

--
Mats