strstr() question

hi, i was implementing strstr() to see how it works.

Code:

---

#include<iostream>
using namespace std;

int main()
{
char str[] = "this is a test";
char*s;
s=strstr(str,"test");
cout<<s<<endl;

}

---

i have two question .

question 1 > what is the full form of strstr() ?

for example, if i write strcpy ---> it means string copy.

similarly what is the meaning of strstr() ?

the syntaxex dont give the full form of this function. can you tell what is the literal meaning?


question 2.


without assigning a memory (by new keyword ) the code is running!!

look, i have simply tested with only char *s; but no memory allocated.

1) most likely string string
2) Read up on pointers more. There is no need to assign memory in this example. s will get the value that is returned by strstr(). In the example it will get the address of the first t in test, or str[10]

>what is the full form of strstr() ?
Does it really matter? Just call it "string string" and be done with it. ;)

>the code is running!!
I'm surprised:

>#include<iostream>
>using namespace std;
These will give you errors in C.

>s=strstr(str,"test");
You didn't include <string.h> for strstr.

>cout<<s<<endl;
If you compile as C, the compiler will complain about this too.

>(by new keyword )
You mean by malloc, since you posted on the C board.

>but no memory allocated
Because strstr returns a pointer to a location within the string you give it as the first argument. The memory already exists, has been initialized (we hope!) and theoretically, you own it. There's no need to allocate memory.

Quote:

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You didn't include <string.h> for strstr.

---

hmmm, but it worked in my compiler. my compiler version

g++ -v

gcc version 3.2.2 20030222 (Red Hat Linux 3.2.2-5)

>but it worked in my compiler
Do you want a cookie? It works on my compiler too (with a warning), but that doesn't make it right.

Quote:

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cout<<s<<endl;

---

Doesn't the above part of the code make it C++, and not plain old C?
Just thought I'd point that out.

>Doesn't the above part of the code make it C++, and not plain old C?
Yes. It was already mentioned, but thank you anyway. :)

Here's a C version of the code. Please don't post C++ code in this forum, instead, use this one.

Code:

---

#include <stdio.h>
 #include <string.h>
 
 int main(void)
 {
  char buf[] = "this is a small message";
  char *p;
 
  if ((p = strstr(buf, "small")) != NULL)
  {
        printf ("p now points to --- %s ---\n", p);
  }
 
  return(0);
 }

---

>hmmm, but it worked in my compiler. my compiler version
>g++ -v
g++ is the GNU C++ compiler. For C, you use gcc.

sorry for posting C++ code.

my demo test was bad. i thought it will return only the matched string. but it is returning the whole string after the matched string.

anyway,

from hammers code can i simply extract "small" to be printed ?



another code

Code:

---

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

 int main(void)
 {
  char buf[] = "this is a small message";
  char *p;

  if ((p = strstr(buf, "is")) != NULL)  // a littele change here
  {
        printf ("p now points to %s \n", p);
  }

  return(0);
 }

---

output
./a.out

p now points to is is a small message


look there is double "is".....why two "is" ?

Look at the message. Now lop off the first two letters. Whaddaya get?

>from hammers code can i simply extract "small" to be printed ?
It takes a little more effort:

Code:

---

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

int main(void)
{
  char buf[] = "this is a small message";
  char *p;

  if ((p = strstr(buf, "small")) != NULL)
  {
    p[ strlen ("small") ] = '\0';
    printf ("p now points to %s \n", p);
  }

  return(0);
}

---

If you don't want to modify the original string then you're stuck with copying the right number of characters to another buffer and then printing that one.

Quote:

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similarly what is the meaning of strstr() ?

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I'd say it means "String string" referring to its usage where it searchs for a string within a string. :)