Change word in a file

thescratchy · 03-18-2010, 04:45 AM

Hello everyone

I have a file :

Code:

<html> 
<head> 
<t i t l e>UHasselt</ t i t l e> 
</head> 
<body>
<font color = ”red”>Dit is de website van de UHasselt</font> 
<br/> 
<br/> 
<font color = ”#123456”>Info over de universiteit</font> 
<br/>
<br/> 
<a	href=”http://www. uhasselt .be”>link</a>
</body> 
</html>

And i want to change the color #123456 into the word green.

Now i know how to go threw the file and write the file.
But how can i change the word? I thought something like this :

I take the length of the word #123456, and with the function strstr() i look at the pointer of the first place. And now i am stuck.

How can i say print everything from the string until that pointer adres.
And after concatenating the word green to this string print everything else after the wordt #123456.

I really appreciate some help. I have examination tomorrow.

thescratchy · 03-18-2010, 04:47 AM

im sorry i forgot to mention i
i am using fgets to read data from the file, so i can work with strings

Tool · 03-18-2010, 04:48 AM

Quote:

How can i say print everything from the string until that pointer adres.

Code:

while(p < p + number_of_chars)
    putc(*p, file);

thescratchy · 03-18-2010, 04:59 AM

OH my god: So simple and yet i couldnt see it

Thank you very much. I got it to work

karthigayan · 03-18-2010, 05:44 AM

Use this code,

Code:

#include<stdio.h>
#include <string.h>
#include<stdlib.h>
char *replace(char *str, char *from, char *to);

main()
{
        char buf[1024];
        FILE *fp;
        char *p;

        if((fp=fopen("file","r+"))==NULL)
        {
                perror("fopen:");
                exit(1);
        }
        else
        {
                while(fgets(buf,sizeof(buf),fp)!=NULL)
                {
                        printf("%s",buf);
                if((p=strstr(buf,"#123456"))!=NULL)
                {
                        printf("%s\n",replace(buf, "#123456", "green"));
                }
                }
        }

}


char *replace(char *str, char *from, char *to)
{
  static char buffer[1024];
  char *p;

  if(!(p = strstr(str, from)))
    return str;

  strncpy(buffer, str, p-str);
  buffer[p-str] = '\0';

  sprintf(buffer+(p-str), "%s%s", to, p+strlen(from));

  return buffer;
}

thescratchy · 03-18-2010, 06:22 AM

Thank you

quzah · 03-18-2010, 06:51 AM

That only replaces the word in-memory, not in-file. You cannot simply seek to a spot, find a word, and overwrite it, without rewriting the entire remainder of the file from that point on, unless the words are the exact same length (or unless the source word is longer than the target word AND you're adding in some form of padding.

Code:

#123456
green

Notice how they are not at all the same length. That means if all you do (and you're not, in the code above, you aren't doing anything to the word on disk) if seek to a spot and write out the word "green", that you'll end up with "green56" on disk. And if it were reversed, you'd be overwriting "green" with a longer word, which would mung up two extra bytes in your file.

Quzah.

rabidbadger · 03-18-2010, 06:54 AM

Quote:

Originally Posted by karthigayan

Use this code

Erm, that code won't actually do what the OP asked for. It will output up to the line with the search string in, the line with the search string in, the same line with the string replaced, and then the rest of the file. As it's a simple fix, I don't know if you made the error for the learning benefit of the OP or not?

Tool · 03-18-2010, 12:38 PM

Yeah Quzah is right.

Open the wanted file for reading, then open another file for writing - you read data from the first file, write it to the second one according to readen data in the first.

After your done, you could open the first file for writing, copy all data from the 2nd file and then delete the 2nd file which you no longer need.

03-18-2010, 04:45 AM	#1
thescratchy Registered User Join Date: Feb 2010 Posts: 74	Change word in a file Hello everyone I have a file : Code: <html> <head> <t i t l e>UHasselt</ t i t l e> </head> <body> <font color = ”red”>Dit is de website van de UHasselt</font> <br/> <br/> <font color = ”#123456”>Info over de universiteit</font> <br/> <br/> <a href=”http://www. uhasselt .be”>link</a> </body> </html> And i want to change the color #123456 into the word green. Now i know how to go threw the file and write the file. But how can i change the word? I thought something like this : I take the length of the word #123456, and with the function strstr() i look at the pointer of the first place. And now i am stuck. How can i say print everything from the string until that pointer adres. And after concatenating the word green to this string print everything else after the wordt #123456. I really appreciate some help. I have examination tomorrow.
thescratchy is offline

03-18-2010, 04:47 AM	#2
thescratchy Registered User Join Date: Feb 2010 Posts: 74	im sorry i forgot to mention i i am using fgets to read data from the file, so i can work with strings
thescratchy is offline

03-18-2010, 04:59 AM	#4
thescratchy Registered User Join Date: Feb 2010 Posts: 74	OH my god: So simple and yet i couldnt see it Thank you very much. I got it to work
thescratchy is offline

03-18-2010, 06:22 AM	#6
thescratchy Registered User Join Date: Feb 2010 Posts: 74	Thank you
thescratchy is offline

03-18-2010, 06:51 AM	#7
quzah +++ OK NO CARRIER Join Date: Oct 2001 Posts: 11,292	That only replaces the word in-memory, not in-file. You cannot simply seek to a spot, find a word, and overwrite it, without rewriting the entire remainder of the file from that point on, unless the words are the exact same length (or unless the source word is longer than the target word AND you're adding in some form of padding. Code: #123456 green Notice how they are not at all the same length. That means if all you do (and you're not, in the code above, you aren't doing anything to the word on disk) if seek to a spot and write out the word "green", that you'll end up with "green56" on disk. And if it were reversed, you'd be overwriting "green" with a longer word, which would mung up two extra bytes in your file. Quzah. __________________ Hundreds of thousands of dipshits can't be wrong. Are you up for the suck?
quzah is offline

03-18-2010, 12:38 PM	#9
Tool Registered User Join Date: Jul 2009 Location: Croatia Posts: 261	Yeah Quzah is right. Open the wanted file for reading, then open another file for writing - you read data from the first file, write it to the second one according to readen data in the first. After your done, you could open the first file for writing, copy all data from the 2nd file and then delete the 2nd file which you no longer need.
Tool is offline

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