How to convert string to float

Question

include lt stdio h gt   include lt string h gt   int main          char s 100    4 0800          printf  float value    4 8f n    float  atoll s         return 0       I expect the output should be 4 08000000 whereas I got only 4 00000000   Is there any way to get the numbers after the dot

User · Answer

Use atof   or strtof    instead   printf  float value    4 8f n   atof s     printf  float value    4 8f n   strtof s  NULL       http   www cplusplus com reference clibrary cstdlib atof  http   www cplusplus com reference cstdlib strtof    atoll   is meant for integers  atof   strtof   is for floats    The reason why you only get 4 00 with atoll   is because it stops parsing when it finds the first non-digit    Note that strtof   requires C99 or C  11

User · Answer

By using sscanf we can convert string to float    include lt stdio h gt       include lt string h gt       int main          char str 100    4 0800             const char s 2     -          char  token      double x        get the first token        token   strtok str  s      sscanf token   f   amp x       printf     f  x         return 0

User · Answer

double x   char  s   s     -2309 12E-15    x   atof s          x   -2309 12E-15     printf  x    4 4f n  x

User · Answer

You want to use the atof   function   http   www cplusplus com reference clibrary cstdlib atof

User · Answer

Why one should not use function atof   to convert string to double   On success  atof   function returns the converted floating point number as a double value  If no valid conversion could be performed  the function returns zero  0 0   If the converted value would be out of the range of representable values by a double  it causes undefined behavior    Refrence http   www cplusplus com reference cstdlib atof   Instead use function strtod    it is more robust   Try this code    include lt stdio h gt   include lt string h gt   include lt stdlib h gt  int main         char s 100     4 0800       printf  Float value    4 8f n  strtod s NULL        return 0      You will get the following output   Float value   4 08000000

User · Answer

Use atof    But this is deprecated  use this instead   const char  flt    4 0800   float f  sscanf flt    f    amp f     http   www cplusplus com reference clibrary cstdlib atof   atof   returns 0 for both failure and on conversion of 0 0  best to not use it

User · Answer

Unfortunately  there is no way to do this easily  Every solution has its drawbacks    Use atof   or strtof   directly  this is what most people will tell you to do and it will work most of the time  However  if the program sets a locale or it uses a library that sets the locale  for instance  a graphics library that displays localised menus  and the user has their locale set to a language where the decimal separator is not    such as fr FR where the separator is    these functions will stop parsing at the   and you will stil get 4 0  Use atof   or strtof   but change the locale  it s a matter of calling setlocale LC ALL  LC NUMERIC       before any call to atof   or the likes  The problem with setlocale is that it will be global to the process and you might interfer with the rest of the program  Note that you might query the current locale with setlocale   and restore it after you re done  Write your own float parsing routine  This might be quite quick if you do not need advanced features such as exponent parsing or hexadecimal floats    Also  note that the value 4 08 cannot be represented exactly as a float  the actual value you will get is 4 0799999237060546875

User · Answer

Main          float rmvivek arni csc      char  c  1234 00       csc atof c       csc  55      printf  the value is  f  csc

[c] How to convert string to float?

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