strcmp

[Neel]

Hi friends,
'm getting weird output with strcmp function.
'm unable to detect the error.

code is:

string myline="[init]";
line=myline.c_s tr();
line[strlen(line)]='\0';

char *value=strtok(l ine,"=");

cout<<strlen(va lue)<<endl;


if(strcmp(value ,"[init]")==0){
cout<<"found"<< endl;
}

even though the value assigned to line is "[init]" (and it prints too
when I do cout) but it doesnt display "found" (satisfy if condition)

[Ian Collins]

Re: strcmp

Neel wrote:

Hi friends,
'm getting weird output with strcmp function.
'm unable to detect the error.
>
code is:
>
string myline="[init]";
line=myline.c_s tr();

What is line?

line[strlen(line)]='\0';
>

myline.c_str() returns a const char*, if you are attempting to modify
that data, all bets are off.

char *value=strtok(l ine,"=");
>

Same here, strtok expects a modifiable (char*) C -style string for its
first input.

cout<<strlen(va lue)<<endl;
>
>
if(strcmp(value ,"[init]")==0){
cout<<"found"<< endl;
}
>
even though the value assigned to line is "[init]" (and it prints too
when I do cout) but it doesnt display "found" (satisfy if condition)

Why mess about with C's archaic string manipulations when your starting
data is a std::string?

--
Ian Collins.

[Neel]

Re: strcmp

On Oct 6, 5:29 pm, Ian Collins <ian-n...@hotmail.co mwrote:

Neel wrote:

Hi friends,
'm getting weird output with strcmp function.
'm unable to detect the error.

>

code is:

>

string myline="[init]";
line=myline.c_s tr();

>
What is line?
>

line[strlen(line)]='\0';

>
myline.c_str() returns a const char*, if you are attempting to modify
that data, all bets are off.
>

      char *value=strtok(l ine,"=");

>
Same here, strtok expects a modifiable (char*) C -style string for its
first input.
>

   cout<<strlen(va lue)<<endl;

>

   if(strcmp(value ,"[init]")==0){
           cout<<"found"<< endl;
   }

>

even though the value assigned to line is "[init]" (and it prints too
when I do cout) but it doesnt display "found" (satisfy if condition)

>
Why mess about with C's archaic string manipulations when your starting
data is a std::string?
>
--
Ian Collins.

I dont know any way to extract data other than strtok

[Ian Collins]

Re: strcmp

Neel wrote:

On Oct 6, 5:29 pm, Ian Collins <ian-n...@hotmail.co mwrote:

>Neel wrote:

>>even though the value assigned to line is "[init]" (and it prints too
>>when I do cout) but it doesnt display "found" (satisfy if condition)

>Why mess about with C's archaic string manipulations when your starting
>data is a std::string?

[please trim responses and don't quote signatures]

>Ian Collins.

>
I dont know any way to extract data other than strtok

Invest some time in learning how how to use std::string. it's well worth
the effort.

--
Ian Collins.

[James Kanze]

Re: strcmp

On Oct 7, 2:29 am, Ian Collins <ian-n...@hotmail.co mwrote:

Neel wrote:

'm getting weird output with strcmp function.
'm unable to detect the error.

code is:

string myline="[init]";
line=myline.c_s tr();

What is line?

line[strlen(line)]='\0';

myline.c_str() returns a const char*, if you are attempting to
modify that data, all bets are off.

And even if it was a copy: if line is correctly '\0' terminated,
this line isn't necessar, and if it isn't, strlen doesn't work.

--
James Kanze (GABI Software) email:james.kan ze@gmail.com
Conseils en informatique orientée objet/
Beratung in objektorientier ter Datenverarbeitu ng
9 place Sémard, 78210 St.-Cyr-l'École, France, +33 (0)1 30 23 00 34

[Jeff Schwab]

Re: strcmp

Ian Collins wrote:

Neel wrote:

>On Oct 6, 5:29 pm, Ian Collins <ian-n...@hotmail.co mwrote:

>>Neel wrote:

>

>>>even though the value assigned to line is "[init]" (and it prints too
>>>when I do cout) but it doesnt display "found" (satisfy if condition)
>>Why mess about with C's archaic string manipulations when your starting
>>data is a std::string?

>
[please trim responses and don't quote signatures]
>

>>Ian Collins.

>I dont know any way to extract data other than strtok

>
Invest some time in learning how how to use std::string. it's well worth
the effort.

See also std::istream_it erator and std::stringstre am.

[Juha Nieminen]

Re: strcmp

Neel wrote:

line[strlen(line)]='\0';

Exactly how do you expect strlen to be able to calculate the length of
the string if it isn't null-terminated already?

[Yannick Tremblay]

Re: strcmp

In article <25c2b063-5f01-420b-987b-21958851275e@v3 9g2000pro.googl egroups.com>,
Neel <a.k.vora@gmail .comwrote:

>On Oct 6, 5:29 pm, Ian Collins <ian-n...@hotmail.co mwrote:

>>
>Why mess about with C's archaic string manipulations when your starting
>data is a std::string?
>>

>
>I dont know any way to extract data other than strtok

On a random linux machine:

$ man strtok
-----------------------------------------------------------------
[... blah blah blah...]
BUGS
Avoid using these functions. If you do use them, note that:

These functions modify their first argument.

These functions cannot be used on constant strings.

The identity of the delimiting character
-------------------------------------------------------------------

That should be enough to motivate you never again to use this function
and to learn better tools.


Yannick