Converting char to float or double

Question

I have a value I read in from a file and is stored as a char   The value is a monetary number               or         I want to convert the char  to a number I can use in calculations  I ve tried atof and strtod and they just give me garbage numbers  What is the correct way to do this  and why is the way I am doing it wrong   This is essentially what I am doing  just the char  value is read in from a file  When I print out the temp and ftemp variables they are just garbage  gigantic negative numbers   Another Edit   I am running exactly this in gcc   include  lt stdio h gt  int main      char  test    12 11    double temp   strtod test NULL    float ftemp   atof test    printf  price   f   f  temp ftemp    return 0       and my output is price  3344336 000000  3344336 000000  Edit  Here is my code  if file    NULL                char curLine  128           while fgets curLine  sizeof curLine  file     NULL                                       tempVal   strtok curLine                             pairs i  name  strdup tempVal               tempVal   strtok NULL                   pairs i  value  strdup tempVal                 i                    fclose file              double temp   strtod pairs 0  value NULL       float ftemp   atof pairs 0  value       printf  price   d   f  temp ftemp     my input file is very simple name  value pairs like this   NAME VALUE NAME VALUE NAME VALUE   with the value being dollar amounts  SOLVED  Thank you all  I was using  d instead of  f and didn t have the right headers included

User · Answer

Code posted by you is correct and should have worked. But check exactly what you have in the char*. If the correct value is to big to be represented, functions will return a positive or negative HUGE_VAL. Check what you have in the char* against maximum values that float and double can represent on your computer.

Check this page for strtod reference and this page for atof reference.

I have tried the example you provided in both Windows and Linux and it worked fine.

User · Answer

You are missing an include    include  lt stdlib h gt   so GCC creates an implicit declaration of atof and atod  leading to garbage values   And the format specifier for double is  f  not  d  that is for integers     include  lt stdlib h gt   include  lt stdio h gt   int main       char  test    12 11     double temp   strtod test NULL     float ftemp   atof test     printf  price   f   f  temp ftemp     return 0       Output    price  12 110000  12 110000

User · Answer

printf  price   d   f  temp ftemp                        This is your problem   Since the arguments are type double and float  you should be using  f for both  since printf is a variadic function  ftemp will be promoted to double       d expects the corresponding argument to be type int  not double     Variadic functions like printf don t really know the types of the arguments in the variable argument list  you have to tell it with the conversion specifier   Since you told printf that the first argument is supposed to be an int  printf will take the next sizeof  int  bytes from the argument list and interpret it as an integer value  hence the first garbage number     Now  it s almost guaranteed that sizeof  int   lt  sizeof  double   so when printf takes the next sizeof  double  bytes from the argument list  it s probably starting with the middle byte of temp  rather than the first byte of ftemp  hence the second garbage number     Use  f for both

[c] Converting char* to float or double

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