strcmp not working in while loop in c

Question

Could somebody help me with this problem? I'm trying to fill a vector with number. The problem (I think) is the condition in there. It is supposed to get out of the while loop when I input an "f" but it doesn't work, although it hasn't got the top numbers of elements before asked.

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

int vecto();
int var;

double* vector; 
char* bv;

int vecto(){

int cont=0,ch;
char v[10];
free(vector);

printf ("¿Number of elements to order?: ");
scanf("%d",&var);
vector = (double*)malloc(var*sizeof(double));
printf("Input numbers press (f) for finish \n");
while((ch = fgetc(stdin)) != EOF && ch != '\n' ){};

do{
    fgets(v,sizeof(v),stdin);
    if((strcmp(v,"f"))!=0){ /*maybe here´s the problem*/
        vector[cont++]=strtod(v,&bv);
    }
} while(!((cont==var) || (strcmp(v,"f")==0)));/*maybe here's the problem*/

printf("\n");

return 0;
}

Please do not add 'fixed' or 'solved' to your title. If your own answer is different from the ones given, you are free to post it as such. — Jongware, Apr 26 '15 at 19:03

score 1 · Answer 1 · answered Apr 26 '15 at 17:18

1

fgets() retains the ENTER from input. Try strcmp(v, "f\n")

answered Apr 26 '15 at 17:18

pmg

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thanks so much now it works but with a little drawback somthing like this: `input:` Number of elements: 4 input numbers: "f" `output:` 0.0000 0.0000 0.0000 49658...........(a big number) – user2461687 Apr 26 '15 at 17:19
The printing is not in your `vecto()` function. I suggest you ask a different question. – pmg Apr 26 '15 at 17:23

score 1 · Answer 2 · answered Apr 26 '15 at 20:39

The following code contains commentary regarding why changes were made

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

// prototypes
int vecto();

int var;

double* vector; 
char* bv;

int vecto()
{

    int cont=0;
    int ch;
    char v[10];

    // at this point, there is no allocated memory to free
    //free(vector);

    printf ("¿Number of elements to order?: ");

    // need to chec the returned value from scanf
    if( 1 != scanf("%d",&var) )
    { // then scanf failed
        perror( "scanf for number of elements to order failed" );
        exit( 1 );
    }

    // implied else, scanf successful

    // need to check the returned value from malloc
    // in C, do not cast the returned value from malloc
    if( NULL == (vector = malloc(var*sizeof(double)) ) )
    { // then malloc failed
        perror( "malloc for vector array failed" );
        exit( 1 );
    }

    // implied else, malloc successful

    printf("Input numbers press (f) for finish \n");

    // any time inputting, need to chack for terminator
    while( ((ch = fgetc(stdin)) != EOF) && (ch != '\n') && (ch != 'f') ){};

    if( 'f' == ch )
    { // then exiting early
        printf( "terminator entered before reading any lines\n" );
        free( vector ); // cleanup
    }

    else
    {
        do{
            if( NULL == fgets(v,sizeof(v),stdin) )
            { // then fgets failed
                perror( "fgets failed" );
                free(vector); // cleanup
                exit( 1 );
            }

            // implied else, fgets successful

            //if((strcmp(v,"f"))!=0)
            // keep code simple
            if( 'f' != v[0] )
            { // then terminator NOT entered by user

                // add 'v', as double, to end of vector
                // need to check that range of conversion was successful
                double tempDouble = strtod(v,&bv);  
                if( ERANGE == errno )
                { // then conversion failed
                    printf( "conversion of %s to double failed", v );
                }
                else
                {// else, conversion successful
                    vector[cont++]=tempDouble;
                }
            }
            else
            { // else, terminator entered by user
                cont = var;
            }
        // terminator already checked
        } while( cont < var );

        printf("\n");
    } // endif

    return 0;
} // end function: vecto

wow, this is kind of complex but I'll study more to understand this, it's great, you're checking every possible error and stuff like that and keep the code simple. Someday (: — user2461687, Apr 26 '15 at 22:42

strcmp not working in while loop in c

2 Answers2