Thread: counting words in a text file...

Hello people,
This is an amazing site for people who are interested in the c language andother wonderful languages too.

Please i have just started learning about the c language, being a novice i stumbled on this piece of work, and i was wondering if you great people can help me.I'm working on a unix system.

The program might be run as follows:

Command line with redirection

a.out "old" "new" <infile >outfile

Note that input is from stdin and output to stdout.(keyboard to screen)
The output should be the same as the input except that all
occurences of the string "old" are replaced by "new".

For example, if you run a.out lara D with input
I love lara
lara wakes me up
then the ouput would be
I love D
D wakes me up

Your program should work for any argument strings including
those that contain spaces. However, newline characters are
not allowed in the "old" or "new" strings. If they are found
print an appropriate usage message to stderr.

I'll appreciate any help sirs/ma's.

If you're using the stl, std::string has a replace() member function. Barring that you have to work out the algorithm yourself.

Happy coding!

Originally posted by Sebastiani
If you're using the stl, std::string has a replace() member function. Barring that you have to work out the algorithm yourself.

Happy coding!

Nice thought, wrong board. C doesn't have classes.

Anyway, as suggested, work out the problem. Write yourself some pseudocode. Write out how you'd do the problem in words first and then turn it into code.

For example, were I trying to find the number 5 in a file, my pseudocode would be something like:

Code:

open the file
while i'm not done with the file
    read a number
    check to see if it's five
       if so, do whatever
       if not, keep looking
close the file

Something to that effect. It's a handy way to break down the problem to get you started.

Quzah.

the general method for a search& replace that I would use is something like: (written in a mix of code and text)

Code:

read "old" & "new" strings
create temp buffer of size strlen(old)+1

read in first strlen(old) characters to buffer

while (c=getc(input)!=EOF)
  {
  if (strcmp(buffer,old)==0)
    {
    print new to output
    clear buffer
    load the next strlen(old) chars
    }else{
    write first char of buffer to output
    shuffle all chars of buffer down one
    read in next char from input to last char of buffer
  }

we now have the whole of output printed, with the changes, except for the last (strlen(old)) characters, which are in the buffer.

Check if buffer == old, if so write new, otherwise just print buffer to output and close.

hope that's roughly intelligible

-mark

Thanks to al lof you for the beautiful and intelligent insights. I'll work on your suggestions.