Thread: Scan some text and replace words

I am having some problems on this one.

I want to read a text and everytime that it reads the word "test four", I want to replace it with the word "view five".


I came up with this code, using the FAQ on this site. Anyone know what I do terribly wrong?

Code:

#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <ctype.h>
#include <sys/types.h>
#include <unistd.h>
#include <math.h>

#define MAX_LINE (128+1)  /* Maximum length of a source line plus one */


int main()
{
    char InputBuffer[MAX_LINE];

    FILE *Infile;
    char *string[MAX_LINE];


    if ((Infile = fopen("input.txt", "r")) == NULL) {
        fprintf(stderr, "Error opening input-file :%s\n", "input.txt");
        exit(1);
    }

    while (!feof(Infile)) {
	(fgets(InputBuffer, MAX_LINE, Infile));
		if ((string = strstr(InputBuffer, "test four")) !=NULL) 
		*string = "view five";
        	printf( "%s\n",InputBuffer);
    }
return(0);

fclose (Infile);
}

I used strstr.. because K&R says that it is the same as strchr, except that it is not for characters, but for strings.

You're trying to replace the text incorrectly. First off, do you mean to have an array of character pointers? Or is that just supposed to be a buffer?

Second, you will need to use something like strcpy to copy one string over the other. Or, simply loop through the characters and replace them that way. Something like:

Code:

s = strstr( inputbuffer, "test four" );
if( s )
{
    char buf[] = "view five", *p;
    for( p = buf; *p; *s++ = *p++ );
}

Now this will only safely work because the string you want to replace is exactly the same length as the one you want to replace it with. You'll have to do a bit more to replace strings of other sizes. Note, this also does nothing for the file itself, it's simply an in-memory replacement.

I'll leave the different size replacement as an exercize to the reader.

Quzah.