Want to protect your cyber security and still get fast solutions? Ask a secure question today.Go Premium

x
?
Solved

C++ : Read a string, and break words by space ....

Posted on 2003-12-10
6
Medium Priority
?
958 Views
Last Modified: 2012-08-14

 Hi C++ Experts,

     I  want  to write a code, which read the first line of a file, and then determine how many columns are there in the first line (so will be in the file). The columns are separated by space. I wrote the following code, but it is kind of ugly and I don't like it ....... I am wondering if anyone could please suggest  some more elegant ways of doing this ? (Perhaps need to incorporate some script ?) I want all in one program, since I would need to declare something later in the code based on the number of columns in the file.

--------------------------------------------------------------------------
#include <fstream>
#include <iostream>
#include <string>

int main()
{
    ifstream input("Person.txt") ;
    ofstream output("temp_file.txt") ;
    string temp ;
    getline(input, temp) ;
    output << temp ;
    output.close() ;

    ifstream input1("temp_file.txt") ;
    cout << "the columns of the file are: " << endl ;
    while(input1){
     string temp1 ;
     input1 >> temp1 ;
     cout << temp1 << endl ;
    }
 
    system("rm temp_file.txt") ;

    return 0 ;
}
------------------------------
and the Person.txt looks like :

Name     Age     Height    Weight    Eye_colors
John     11      5'2"       100lbs    brown
Mary     15      6'         150lbs    green
Dave     12      5'5"       140lbs    blue
0
Comment
Question by:meow00
  • 3
  • 2
6 Comments
 
LVL 86

Expert Comment

by:jkr
ID: 9912719
You could either use 'strtok()'

/* STRTOK.C: In this program, a loop uses strtok
 * to print all the tokens (separated by commas
 * or blanks) in the string named "string".
 */

#include <string.h>
#include <stdio.h>

char string[] = "A string\tof ,,tokens\nand some  more tokens";
char seps[]   = " ,\t\n";
char *token;

void main( void )
{
   printf( "%s\n\nTokens:\n", string );
   /* Establish string and get the first token: */
   token = strtok( string, seps );
   while( token != NULL )
   {
      /* While there are tokens in "string" */
      printf( " %s\n", token );
      /* Get next token: */
      token = strtok( NULL, seps );
   }
}

or

http://www.boost.org/libs/tokenizer/tokenizer.htm

0
 
LVL 11

Expert Comment

by:bcladd
ID: 9912755
_Accelerated C++_ by Koenig and Moo has a good exmaple of a string splitter, too. Even without the book you can get their source code at http://www.acceleratedcpp.com/. It takes a string and splits it into a vector of strings, one entry per "word" for some definition of word (non-space between spaces).

I would suggest the book, too, since it is a good read.

-bcl
0
 
LVL 1

Author Comment

by:meow00
ID: 9913010
Hello,

   Thanks for the answers.... I just have one more question about jkr's answer. What if I have a string "string" as follows :
--------------------------------
#include <string>
#include <cstdio>
#include <iostream>
#include <fstream>

char seps[]   = " ,.!a\t\n";
char *token;
string meow = "I am the laziest cat in the world...meow " ;
char woof[] = " I am,a happy dog !" ;

void main( void )
{
//   token = strtok(meow.c_str(), seps) ;  //...line01
   token = strtok(woof,seps) ;
   while(token != NULL){
    cout << token << endl ;
    token = strtok(NULL, seps) ;
   }
}
---------------------------------------------
 line01 doesn't work now ......
 Is there anyway to make line01 work ? thanks !

 meow ......
~
0
Concerto Cloud for Software Providers & ISVs

Can Concerto Cloud Services help you focus on evolving your application offerings, while delivering the best cloud experience to your customers? From DevOps to revenue models and customer support, the answer is yes!

Learn how Concerto can help you.

 
LVL 11

Assisted Solution

by:bcladd
bcladd earned 160 total points
ID: 9913086
You need to copy the contents of the string into an array of char because strtok is brutally destructive to the character string tokenized.

Try something like

char * meowCh = new char[meow.length() + 1];
strcpy(meowCh, meow.c_str());

and then tokenize meowCh and delete[] when you're done.

-bcl
0
 
LVL 86

Accepted Solution

by:
jkr earned 320 total points
ID: 9913124
>>is brutally destructive to the character string tokenized

Yup - I'd use

  char* woof = strdup(meow.c_str()) ;
  token = strtok(woof,seps) ;

// ...

  free(woof);

though...
0
 
LVL 11

Expert Comment

by:bcladd
ID: 9913153
Sure, show an easier way to accomplish the same thing.

<smile>

-bcl
0

Featured Post

What does it mean to be "Always On"?

Is your cloud always on? With an Always On cloud you won't have to worry about downtime for maintenance or software application code updates, ensuring that your bottom line isn't affected.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Unlike C#, C++ doesn't have native support for sealing classes (so they cannot be sub-classed). At the cost of a virtual base class pointer it is possible to implement a pseudo sealing mechanism The trick is to virtually inherit from a base class…
This article will show you some of the more useful Standard Template Library (STL) algorithms through the use of working examples.  You will learn about how these algorithms fit into the STL architecture, how they work with STL containers, and why t…
The goal of the tutorial is to teach the user how to use functions in C++. The video will cover how to define functions, how to call functions and how to create functions prototypes. Microsoft Visual C++ 2010 Express will be used as a text editor an…
The goal of the video will be to teach the user the difference and consequence of passing data by value vs passing data by reference in C++. An example of passing data by value as well as an example of passing data by reference will be be given. Bot…

578 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question