Inserting text into a file

Hi all,

I'm having difficulties inserting a string into a text file. Here's my code:

Code:

---


int main() {

        FILE *f;
        char c=0;
        int br=0;

        if ((f=fopen("fajl.htm", "r+"))==NULL) {
                exit(1);
        }

        while ((c=fgetc(f))!=EOF) {

                if (c=='&') {
                                fputs("blah", f);
                                printf("Job done.\n");
                }
        }

        fclose(f);

        return 0;

}

---

What I am trying to do is insert a string after a certain character. This code does not work for some reason, when it goes through the file and finds this specific character, it will not insert my string, but continue to the next character.

What am I doing wrong?

you're trying to write to the file right? fix the mode then..

besides , the while loop would execute anyway regardless if the file was successfuly opened or not.

Quote:

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Originally Posted by Brain Cell

you're trying to write to the file right? fix the mode then..

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If I use the w mode, it will delete the contents of the file before writing.

You can use the a mode to append.

Guys, "r+" is the correct mode for him. "a" would stick him at the end of the file. He wants to insert after a certain character in the file. And how would the while() loop execute if the file is incorrectly opened if exit() is being called in that situation?

It would be helpful to see the contents of the file.

NOTE: You can't "insert" text in a file. You'll overwrite what's already there. You can read in the rest of the file after that point to a buffer, write your new text, and then dump the buffer back onto the end of the file though.

http://www.eskimo.com/~scs/C-faq/q19.14.html
http://www.eskimo.com/~scs/C-faq/q12.30.html

Quote:

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Originally Posted by itsme86

NOTE: You can't "insert" text in a file. You'll overwrite what's already there. You can read in the rest of the file after that point to a buffer, write your new text, and then dump the buffer back onto the end of the file though.

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What I'm actually trying to do is replace ampersands (&) in a HTML file with &. So when the ampersand is found, the program would insert amp; after it.

What you're suggesting is to define a large character array where I'd put what remains in the file after the specific character? How large should the array be, considering that the HTML files vary from 5 to 80 KB?

That's one option. Another option would be to use a separate output file. You could read each character in the file like you are now. Write the character to the output file and then check if it was an ampersand. If it was, also write "amp" to the output file.

To find out the size of the file (in case you go with the first option) you can use stat() on the file. The st_size member is the size of the file. Then you can malloc() that many bytes for the buffer.

Code:

---

while( (c = fgetc( infile )) != EOF )
{
    if( c == '&' )
    {
        fprintf( outfile, "&" );
    }
    else
    {
        fputc( c, outfile );
    }
}

---

You did say "every &". ;)

Quzah.

Quote:

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Originally Posted by itsme86

That's one option. Another option would be to use a separate output file. You could read each character in the file like you are now. Write the character to the output file and then check if it was an ampersand. If it was, also write "amp" to the output file.

To find out the size of the file (in case you go with the first option) you can use stat() on the file. The st_size member is the size of the file. Then you can malloc() that many bytes for the buffer.

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Thanks, you've been much helpful!!

Quote:

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Guys, "r+" is the correct mode for him. "a" would stick him at the end of the file.

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aw i didn't notice the plus nor that you actually want to write AND read from the file.

sorry Ariod..

Quote:

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Originally Posted by itsme86

That's one option. Another option would be to use a separate output file. You could read each character in the file like you are now. Write the character to the output file and then check if it was an ampersand. If it was, also write "amp" to the output file.

To find out the size of the file (in case you go with the first option) you can use stat() on the file. The st_size member is the size of the file. Then you can malloc() that many bytes for the buffer.

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The idea is a good one, however this is assuming the op is on unix or unix variant.

Quote:

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Originally Posted by caroundw5h

The idea is a good one, however this is assuming the op is on unix or unix variant.

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True enough. I failed to mention that. Thanks.