Using the getline() function

[taverasme]

Hi all,

First time poster here, I've referenced posts here on daniweb in the past and it has always been helpful, thanks! But I can't find the answer to this particular problem here on the forums.

I need to write a basic string parser as part of a coding assignment here at penn state. I have completed the assignment using getc, but bonus points are offered for a solution using getline.

The getline() man page (http://linux.die.net/man/3/getline) requires stdio.h and stdlib.h for getline to compile.

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

int main()
{
    //welcome to main!
    //we need our input values!
    
    char inputstr[128];
    
    while(1)
    {
            if(feof(stdin) != 0)
            { break; }
            
            getline(&inputstr, 128, NULL);
            //did that work!?
            printf("input string is : %s\n", inputstr);            
    }
    
    getc(stdin);
    return 0;
    
}

This code wont even compile!!
Here is the compiler error and log, from Dev-C++(set for standard C)

LOG:

Compiler: Default compiler
Executing  gcc.exe...
gcc.exe "E:\pr1\proj1.c" -o "E:\pr1\proj1.exe"    -I"E:\Dev-Cpp\include"   -L"E:\Dev-Cpp\lib" 
C:\DOCUME~1\xxxxxx\LOCALS~1\Temp/ccwrbaaa.o(.text+0x61):proj1.c: undefined reference to `getline'
collect2: ld returned 1 exit status

Execution terminated

ERROR:

[Linker error] undefined reference to `getline' 
  ld returned 1 exit status

Unfortunately, my go-to book, C:ARM(C a reference manual) doesnt even have this function! :(

Thanks for any help or insight you can provide!

-Tav

EDIT:

I realize that getline is not a standard C function, but even when I compile using

-std=c99

I get the same error!

[gerard4143]

Try something like below:

#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main()
{

	char inputstr[128];
	char *cptr = &inputstr[0];
	size_t thesize = 128;
    
	while(1)
	{
	    if(feof(stdin) != 0)
	    { break; }
	    
	    getline(&cptr, &thesize, stdin);

	    printf("input string is : %s\n", inputstr);            
	}

	getc(stdin);
    return 0;
    
}

[gerard4143]

Or you could:

#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main()
{
	char *cptr = NULL;
	size_t thesize = 0;
    
	while(1)
	{
	    if(feof(stdin) != 0)
	    { break; }
	    
	    getline(&cptr, &thesize, stdin);

	    printf("input string is : %s\n", cptr);

		free(cptr); 
		cptr =  NULL;           
	}

	getc(stdin);
    return 0;
    
}

[Dave Sinkula]

Try something like below:

With the MinGW version of gcc:

main.c
main.c: In function `main':
main.c:18: warning: implicit declaration of function `getline'
Linking...
Debug/main.o: In function `main':
C:/Users/Dave/Projects/scratch/main.c:18: undefined reference to `_getline'
collect2: ld returned 1 exit status
*** Errors occurred during this build ***

I need to write a basic string parser as part of a coding assignment here at penn state. I have completed the assignment using getc, but bonus points are offered for a solution using getline.

Are they expecting you to then be using a *nux platform?

I realize that getline is not a standard C function, but even when I compile using

-std=c99

I get the same error!

Yes. It's not standard in either C90 or C99. ?

[Ancient Dragon]

>>my go-to book, C:ARM(C a reference manual) doesnt even have this function!
because getline() is not a standard C function. Its a standard c++ function, not C. If your compiler implements a C getline() function than ok, but don't expect to read about it in any text book.

[gerard4143]

Linux man states

CONFORMING TO
Both getline() and getdelim() are GNU extensions. They are available
since libc 4.6.27.

[servooo]

Hi,i need help please,when i compile cpp file it give me error

main.cpp:158: error: 'getline' was not declared in this scope

i am newbie and i dont know what to do...i find some info about problems with getline on mac os x....the program run without problem in ubuntu but on os x i have this error.

Thanks.

[gerard4143]

First question, are you writing a C++ program or a C program? I ask because this is the C section and your error indicates a .cpp file.

[Nikolas9896]

Hello! How are can "free(cptr);" If you dosen't used to dynamic memorys?
You will helped -** man getline** - in this scope you could see how use that function.