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

char *value=strtok(line,"=");

cout<<strlen(value)<<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]

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

code is:

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

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(line,"=");

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

cout<<strlen(value)<<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?

 

[Neel]

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

code is:

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

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(line,"=");

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

   cout<<strlen(value)<<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?

I dont know any way to extract data other than strtok

 

[Ian Collins]

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]

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.

 

[James Kanze]

Neel wrote:

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

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.

 

[Juha Nieminen]

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?