Convert a string into a double-precision number
#include <stdlib.h> double strtod( const char *ptr, char **endptr ); float strtof( const char *ptr, char **endptr ); long double strtold( const char *ptr, char **endptr );
libc
Use the -l c option to qcc to link against this library. This library is usually included automatically.
The strtod(), strtof(), and strtold() functions convert the string pointed to by ptr into a double-precision representation:
This function: | Returns: |
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strtod() | double |
strtof() | float |
strtold() | long double |
These functions skip any leading white space, and then look for a subject sequence that consists of an optional plus or minus sign followed by one of the following:
The conversion ends at the first unrecognized character. If endptr isn't NULL, a pointer to the unrecognized character is stored in the object endptr points to.
The converted value. If the correct value would cause overflow, plus or minus HUGE_VAL is returned according to the sign, and errno is set to ERANGE. If the correct value would cause underflow, a value with a magnitude no greater than the smallest normalized positive number in the return type is returned and errno is set to ERANGE.
#include <stdio.h> #include <stdlib.h> int main( void ) { double pi; pi = strtod( "3.141592653589793", NULL ); printf( "pi=%17.15f\n",pi ); return EXIT_SUCCESS; }
Safety: | |
---|---|
Cancellation point | No |
Interrupt handler | No |
Signal handler | Yes |
Thread | Yes |