DOKK / manpages / debian 11 / avr-libc / random.3avr.en
avr_stdlib(3avr) avr-libc avr_stdlib(3avr)

avr_stdlib - <stdlib.h>: General utilities


double atof (const char *__nptr)


char * ltoa (long val, char *s, int radix)
char * utoa (unsigned int val, char *s, int radix)
char * ultoa (unsigned long val, char *s, int radix)
long random (void)
void srandom (unsigned long __seed)
long random_r (unsigned long *__ctx)
char * itoa (int val, char *s, int radix)
#define RANDOM_MAX 0x7FFFFFFF

Note that these functions are not located in the default library, libc.a, but in the mathematical library, libm.a. So when linking the application, the -lm option needs to be specified.
char * dtostre (double __val, char *__s, unsigned char __prec, unsigned char __flags)
char * dtostrf (double __val, signed char __width, unsigned char __prec, char *__s)
#define DTOSTR_ALWAYS_SIGN 0x01 /* put '+' or ' ' for positives */
#define DTOSTR_PLUS_SIGN 0x02 /* put '+' rather than ' ' */
#define DTOSTR_UPPERCASE 0x04 /* put 'E' rather 'e' */
#define EXIT_SUCCESS 0
#define EXIT_FAILURE 1 

#include <stdlib.h>

This file declares some basic C macros and functions as defined by the ISO standard, plus some AVR-specific extensions.

Bit value that can be passed in flags to dtostre().

Bit value that can be passed in flags to dtostre().

Bit value that can be passed in flags to dtostre().

Unsuccessful termination for exit(); evaluates to a non-zero value.

Successful termination for exit(); evaluates to 0.

Highest number that can be generated by random().

The atof() function converts the initial portion of the string pointed to by nptr to double representation.

It is equivalent to calling

strtod(nptr, (char **)0);

The dtostre() function converts the double value passed in val into an ASCII representation that will be stored under s. The caller is responsible for providing sufficient storage in s.

Conversion is done in the format '[-]d.ddde±dd' where there is one digit before the decimal-point character and the number of digits after it is equal to the precision prec; if the precision is zero, no decimal-point character appears. If flags has the DTOSTR_UPPERCASE bit set, the letter 'E' (rather than 'e' ) will be used to introduce the exponent. The exponent always contains two digits; if the value is zero, the exponent is '00'.

If flags has the DTOSTR_ALWAYS_SIGN bit set, a space character will be placed into the leading position for positive numbers.

If flags has the DTOSTR_PLUS_SIGN bit set, a plus sign will be used instead of a space character in this case.

The dtostre() function returns the pointer to the converted string s.

The dtostrf() function converts the double value passed in val into an ASCII representationthat will be stored under s. The caller is responsible for providing sufficient storage in s.

Conversion is done in the format '[-]d.ddd'. The minimum field width of the output string (including the possible '.' and the possible sign for negative values) is given in width, and prec determines the number of digits after the decimal sign. width is signed value, negative for left adjustment.

The dtostrf() function returns the pointer to the converted string s.

Convert an integer to a string. The function itoa() converts the integer value from val into an ASCII representation that will be stored under s. The caller is responsible for providing sufficient storage in s.

Note

The minimal size of the buffer s depends on the choice of radix. For example, if the radix is 2 (binary), you need to supply a buffer with a minimal length of 8 * sizeof (int) + 1 characters, i.e. one character for each bit plus one for the string terminator. Using a larger radix will require a smaller minimal buffer size.

Warning

If the buffer is too small, you risk a buffer overflow.

Conversion is done using the radix as base, which may be a number between 2 (binary conversion) and up to 36. If radix is greater than 10, the next digit after '9' will be the letter 'a'.

If radix is 10 and val is negative, a minus sign will be prepended.

The itoa() function returns the pointer passed as s.

Convert a long integer to a string. The function ltoa() converts the long integer value from val into an ASCII representation that will be stored under s. The caller is responsible for providing sufficient storage in s.

Note

The minimal size of the buffer s depends on the choice of radix. For example, if the radix is 2 (binary), you need to supply a buffer with a minimal length of 8 * sizeof (long int) + 1 characters, i.e. one character for each bit plus one for the string terminator. Using a larger radix will require a smaller minimal buffer size.

Warning

If the buffer is too small, you risk a buffer overflow.

Conversion is done using the radix as base, which may be a number between 2 (binary conversion) and up to 36. If radix is greater than 10, the next digit after '9' will be the letter 'a'.

If radix is 10 and val is negative, a minus sign will be prepended.

The ltoa() function returns the pointer passed as s.

The random() function computes a sequence of pseudo-random integers in the range of 0 to RANDOM_MAX (as defined by the header file <stdlib.h>).

The srandom() function sets its argument seed as the seed for a new sequence of pseudo-random numbers to be returned by rand(). These sequences are repeatable by calling srandom() with the same seed value.

If no seed value is provided, the functions are automatically seeded with a value of 1.

Variant of random() that stores the context in the user-supplied variable located at ctx instead of a static library variable so the function becomes re-entrant.

Pseudo-random number generator seeding; see random().

Convert an unsigned long integer to a string. The function ultoa() converts the unsigned long integer value from val into an ASCII representation that will be stored under s. The caller is responsible for providing sufficient storage in s.

Note

The minimal size of the buffer s depends on the choice of radix. For example, if the radix is 2 (binary), you need to supply a buffer with a minimal length of 8 * sizeof (unsigned long int) + 1 characters, i.e. one character for each bit plus one for the string terminator. Using a larger radix will require a smaller minimal buffer size.

Warning

If the buffer is too small, you risk a buffer overflow.

Conversion is done using the radix as base, which may be a number between 2 (binary conversion) and up to 36. If radix is greater than 10, the next digit after '9' will be the letter 'a'.

The ultoa() function returns the pointer passed as s.

Convert an unsigned integer to a string. The function utoa() converts the unsigned integer value from val into an ASCII representation that will be stored under s. The caller is responsible for providing sufficient storage in s.

Note

The minimal size of the buffer s depends on the choice of radix. For example, if the radix is 2 (binary), you need to supply a buffer with a minimal length of 8 * sizeof (unsigned int) + 1 characters, i.e. one character for each bit plus one for the string terminator. Using a larger radix will require a smaller minimal buffer size.

Warning

If the buffer is too small, you risk a buffer overflow.

Conversion is done using the radix as base, which may be a number between 2 (binary conversion) and up to 36. If radix is greater than 10, the next digit after '9' will be the letter 'a'.

The utoa() function returns the pointer passed as s.

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Fri Jan 1 2021 Version 2.0.0