replace word in a file

[tubby123]

Hey, this one is agaain from File-handling

How do you replace a word in a file with another word.
The algorithm should be somewhat like this

1)Read (fgets) the entire line into a buffer. Locate the word/ position of the word.
2)From that point onwards, OVERWRITE the contents in the buffer with the NEW WORD.
3)Put (fprintf) the modified buffer back into the file.

Fine BUT, doesnt this just shout out that, it'll work only if the word-to-be-replaced and the new-word are of the same length. Otherwise,(assuming the new word is higher in length) to accommodate the new word, it'll over-write over a part of the file which is actually necessary.

Sample Output of error case
---------------------------

File contents : goodsite
Replace good with great
File contents : greatite - WRONG
Expected correct output :greatsite

Please give me your valuable suggestions

[tubby123]

Hey, this one is agaain from File-handling

How do you replace a word in a file with another word.
The algorithm should be somewhat like this

1)Read (fgets) the entire line into a buffer. Locate the word/ position of the word.
2)From that point onwards, OVERWRITE the contents in the buffer with the NEW WORD.
3)Put (fprintf) the modified buffer back into the file.

Fine BUT, doesnt this just shout out that, it'll work only if the word-to-be-replaced and the new-word are of the same length. Otherwise,(assuming the new word is higher in length) to accommodate the new word, it'll over-write over a part of the file which is actually necessary.

Sample Output of error case
---------------------------

File contents : goodsite
Replace good with great
File contents : greatite - WRONG
Expected correct output :greatsite

Please give me your valuable suggestions

hey guys, its me again, just struck me now.
Lets assume the case i gave above , replace good with great

How about this
--------------
1)Find the location of word-to-replace ,ie good(in our case), (here first place itself, never mind)
2)Write all the characters until this into a file2(In this case, nothing precedes good, that ok)
3)On encountering the word-to-replace, write the word-with-which-to-replace into the file2
4)Move the pointer of file1 as long as the word-to-replace is over.
5)Then again write the remaining contents into file2
6)Delete file1
7)Rename file2 to file1
For newcomers like me who are reading this some day, YES, both 6 and 7 are very much possible in C

Word of caution
---------------
Sooooooo Brute force.

Please give me your valuable suggestions, if and since there is a better algorithm

[Adak]

Good! Now tell me when you know that the word to replace, has ended?

1) a space is reached, obviously ;)

2) an end of line char is reached, of course

3) what about EOF (end of file), and punctuation char's?

Lots of details when you deal with strings, language, etc. Great start though.

[tubby123]

Hey Adak, feels great talking to you.
I actually referred 1 of the posts in which you had posted http://www.daniweb.com/software-development/c/threads/367273. Thanks a lot for that :)

Coming to the problem, how do you know where the word-to-replace has ended, cat we just do a

while(*word-to-replace)
{
 c=getc(fp_file1); //so that the file pointer keeps incrementing
}

I mean everytime you do a getc(fp_file1) , getc points to the next character in the file right ????
Isnt this enough insted of going case-by-case.

Have i understood your comment . I think i have not.
Do reply.

[Adak]

Have you considered using strstr()? It's made for this, imo. Look at it in your help file, and see what you think.

Then make a little test case and program, with strstr(), or with your earlier idea, or both, and see how it works. You know you're close, so it won't be a waste of time. Be sure the test case has some "difficult" text, which includes most or all of the above details discussed herein.

There's always more than one way to do something. If I have a very small number of words, I tend to use a small buffer, and go char by char (ie., small), to do this. If I have a lot of text, then I tend to go with a very big buffer, and use strstr(). I believe you should know how to use either one, depending on what you think is best, at that time, for that problem.