| Topic: |
DEVELOP > c-Plus-Plus |
| User: |
"" |
| Date: |
29 Mar 2006 09:01:03 AM |
| Object: |
strtok problem |
Hi,
I need to split the value stored in a string and store them to another
charrecter array.I am using strtok function.But i am getting invalid
output when there is no value between delimiter
my code
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
void main()
{
char *pch;
char *parameters[4];
int paramcount=0;
char b[]="mani,raju,musa,kumar";
pch=strtok(b,",");
while (pch != NULL)
{
//parameters[paramcount]=pch;
parameters[paramcount]=(char*)malloc(strlen(pch) + 1);
strcpy(parameters[paramcount],pch);
paramcount++;
pch = strtok (NULL, ",");
}//while (pch != NULL)
for(int t=0;t<4;t++)
printf("\n%s\n",parameters[t]);
}
the above code works fine.when i change the input as follows
char b[]="mani,,,kumar"
The output is not correct.
How to free the memory allocated?
how to handle strtok when there is no value between delimiter
Regards,
Manikandan
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| User: "Pete Becker" |
|
| Title: Re: strtok problem |
29 Mar 2006 10:31:59 AM |
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wrote:
the above code works fine.when i change the input as follows
char b[]="mani,,,kumar"
The output is not correct.
Well, that depends on what "correct" means. According to the definition
of strotk, the new input has two data fields, separated by three commas.
strtok swallows all consecutive occurrences of characters in the
delimiter string.
How to free the memory allocated?
Same way you allocated it: step through the array and call delete[] on
each allocated block.
how to handle strtok when there is no value between delimiter
strtok doesn't do that. You can use strcspn if you don't mind doing a
little more bookkeeping. Or you can use the STL algorithm find_first_of
to find the next occurrence of the delimiter in a C string. Or, at the
cost of a little more overhead, copy the text into a C++ string object,
and use its member function find_first_of.
--
Pete Becker
Roundhouse Consulting, Ltd.
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| User: "Puppet_Sock" |
|
| Title: Re: strtok problem |
29 Mar 2006 09:36:50 AM |
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wrote:
[snip]
pch=strtok(b,",");
[snip]
the above code works fine.when i change the input as follows
char b[]="mani,,,kumar"
The output is not correct.
How to free the memory allocated?
how to handle strtok when there is no value between delimiter
I am convinced that the main purpose of the strtok function being
in the library is to catch new coders in the knees.
Carefully read up on the strtok function in your compiler's docs.
Note what happens when there are multiple delimeters with
nothing between them. So, your "not working" input will be
equivalent to
char b[]="mani,kumar"
that is, there's no way for you to use strtok to get those missing
fields in the middle.
Also, read up in your docs about the various warnings and caveats
about using strtok. The security warning that should be there, for
example. And the warning about a static variable being used so that
multiple overlapping calls with different strings to tokenize will
interfere with eachother.
My opinion: Don't use strtok. Roll up your own parsing class,
preferably using std::string instead of char arrays. But even if
you can't use std::string, drop the use of strtok.
Write yourself a class that takes your input, copies it to an
internal buffer, then parses it out to a vector of tokens. Give
it the behaviour you need it to have with regard to missing
entries. Make sure you follow all the "motherhood" rules
about class design such as the rule of 3, and so on. Then
give it a small number of "get" funcs that pull out the number
of items in the vector, and the "nth" item in the list. You
can then have a really good time deciding what to do about
such things as asking for an element past the end (the
7th element when there are only 4, as an example.)
You can even have such things as multiple delimeters,
delims that are more than one char, even calculated delims
that depend on rules such as a space after a period is a
delim, but a space after anything else is not.
Socks
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| User: "Sgt. York" |
|
| Title: Re: strtok problem |
29 Mar 2006 10:41:49 AM |
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Puppet_Sock wrote:
plmanikandan@gmail.com wrote:
[snip]
pch=strtok(b,",");
[snip]
the above code works fine.when i change the input as follows
char b[]="mani,,,kumar"
The output is not correct.
How to free the memory allocated?
how to handle strtok when there is no value between delimiter
I am convinced that the main purpose of the strtok function being
in the library is to catch new coders in the knees.
Carefully read up on the strtok function in your compiler's docs.
Note what happens when there are multiple delimeters with
nothing between them. So, your "not working" input will be
equivalent to
char b[]="mani,kumar"
that is, there's no way for you to use strtok to get those missing
fields in the middle.
Also, read up in your docs about the various warnings and caveats
about using strtok. The security warning that should be there, for
example. And the warning about a static variable being used so that
multiple overlapping calls with different strings to tokenize will
interfere with eachother.
My opinion: Don't use strtok. Roll up your own parsing class,
preferably using std::string instead of char arrays. But even if
you can't use std::string, drop the use of strtok.
Write yourself a class that takes your input, copies it to an
internal buffer, then parses it out to a vector of tokens. Give
it the behaviour you need it to have with regard to missing
entries. Make sure you follow all the "motherhood" rules
about class design such as the rule of 3, and so on. Then
give it a small number of "get" funcs that pull out the number
of items in the vector, and the "nth" item in the list. You
can then have a really good time deciding what to do about
such things as asking for an element past the end (the
7th element when there are only 4, as an example.)
You can even have such things as multiple delimeters,
delims that are more than one char, even calculated delims
that depend on rules such as a space after a period is a
delim, but a space after anything else is not.
Socks
Better yet, use John Bandela's Boost tokenizer (www.boost.org). From
there, you'll likely discover other boost delicacies that will make the
library almost indispensable.
-York
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| User: "Daniel T." |
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| Title: Re: strtok problem |
30 Mar 2006 01:05:37 AM |
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In articl
<1143644463.592006.230960@g10g2000cwb.googlegroups.com>
wrote
Hi
I need to split the value stored in a string and store them t
anothe
charrecter array.I am using strtok function.But i am getting invali
output when there is no value between delimite
my cod
#include<stdio.
#include<string.
#include<stdlib.
void main(
char *pch
char *parameters[4]
int paramcount=0
char b[]="mani,raju,musa,kumar"
pch=strtok(b,",")
while (pch != NULL
//parameters[paramcount]=pch
parameters[paramcount]=(char*)malloc(strlen(pch) + 1)
strcpy(parameters[paramcount],pch)
paramcount++
pch = strtok (NULL, ",")
}//while (pch != NULL
for(int t=0;t<4;t++
printf("\n%s\n",parameters[t])
the above code works fine.when i change the input as follow
char b[]="mani,,,kumar
The output is not correct
How to free the memory allocated
how to handle strtok when there is no value between delimite
I'm thinking your confused as accidentally posted this in a C++
newsgroup instead of a C newsgroup. Could that be the case? If not..
I suggest you use some standard C++ components
#include <algorithm> // for copy & fin
#include <iostream> // for cou
#include <iterator> // for ostream_iterato
#include <string
#include <vector
using namespace std
int main(
//char b[]="mani,raju,musa,kumar"
char b[]="mani,,,kumar"
vector<string> vec
const char* first = b
const char* last = b + strlen( b )
while ( first != last )
const char* next = find( first, last, ',' )
vec.push_back( string( first, next - first ) )
first = min( next + 1, last )
copy( vec.begin(), vec.end()
ostream_iterator<string>( cout
"\n" ) )
--
Magic depends on tradition and belief. It does not welcom
observation
nor does it profit by experiment. On the other hand, science is base
on experience; it is open to correction by observation and experiment
.
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| User: "Daniel T." |
|
| Title: Re: strtok problem |
29 Mar 2006 07:20:26 PM |
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In article <1143644463.592006.230960@g10g2000cwb.googlegroups.com>,
wrote:
Hi,
I need to split the value stored in a string and store them to another
charrecter array.I am using strtok function.But i am getting invalid
output when there is no value between delimiter
my code
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
void main()
{
char *pch;
char *parameters[4];
int paramcount=0;
char b[]="mani,raju,musa,kumar";
pch=strtok(b,",");
while (pch != NULL)
{
//parameters[paramcount]=pch;
parameters[paramcount]=(char*)malloc(strlen(pch) + 1);
strcpy(parameters[paramcount],pch);
paramcount++;
pch = strtok (NULL, ",");
}//while (pch != NULL)
for(int t=0;t<4;t++)
printf("\n%s\n",parameters[t]);
}
the above code works fine.when i change the input as follows
char b[]="mani,,,kumar"
The output is not correct.
How to free the memory allocated?
how to handle strtok when there is no value between delimiter
I'm thinking your confused as accidentally posted this in a C++
newsgroup instead of a C newsgroup. Could that be the case? If not...
I suggest you use some standard C++ components:
#include <algorithm> // for copy & find
#include <iostream> // for cout
#include <iterator> // for ostream_iterator
#include <string>
#include <vector>
using namespace std;
int main()
{
//char b[]="mani,raju,musa,kumar";
char b[]="mani,,,kumar";
vector<string> vec;
const char* first = b;
const char* last = b + strlen( b );
while ( first != last ) {
const char* next = find( first, last, ',' );
vec.push_back( string( first, next - first ) );
first = min( next + 1, last );
}
copy( vec.begin(), vec.end(),
ostream_iterator<string>( cout, "\n" ) );
}
--
Magic depends on tradition and belief. It does not welcome observation,
nor does it profit by experiment. On the other hand, science is based
on experience; it is open to correction by observation and experiment.
.
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