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rand (3)
  • rand (1) ( Solaris man: Команды и прикладные программы пользовательского уровня )
  • rand (1) ( Linux man: Команды и прикладные программы пользовательского уровня )
  • >> rand (3) ( Solaris man: Библиотечные вызовы )
  • rand (3) ( FreeBSD man: Библиотечные вызовы )
  • rand (3) ( Русские man: Библиотечные вызовы )
  • rand (3) ( Linux man: Библиотечные вызовы )
  • rand (3) ( POSIX man: Библиотечные вызовы )
  •  

    NAME

    rand, srand, rand_r - simple random-number generator
     
    

    SYNOPSIS

    #include <stdlib.h>
    
    int rand(void);
    

    void srand(unsigned int seed);
    

    int rand_r(unsigned int *seed);
    

     

    DESCRIPTION

    The rand() function uses a multiplicative congruential random-number generator with period 2^32 that returns successive pseudo-random numbers in the range of 0 to RAND_MAX (defined in <stdlib.h>).

    The srand() function uses the argument seed as a seed for a new sequence of pseudo-random numbers to be returned by subsequent calls to rand(). If srand() is then called with the same seed value, the sequence of pseudo-random numbers will be repeated. If rand() is called before any calls to srand() have been made, the same sequence will be generated as when srand() is first called with a seed value of 1.

    The rand_r() function has the same functionality as rand() except that a pointer to a seed seed must be supplied by the caller. If rand_r() is called with the same initial value for the object pointed to by seed and that object is not modified between successive calls to rand_r(), the same sequence as that produced by calls to rand() will be generated.

    The rand() and srand() functions provide per-process pseudo-random streams shared by all threads. The same effect can be achieved if all threads call rand_r() with a pointer to the same seed object. The rand_r() function allows a thread to generate a private pseudo-random stream by having the seed object be private to the thread.  

    USAGE

    The spectral properties of rand() are limited. The drand48(3C) function provides a better, more elaborate random-number generator.

    When compiling multithreaded applications, the _REENTRANT flag must be defined on the compile line. This flag should be used only in multithreaded applications.  

    ATTRIBUTES

    See attributes(5) for descriptions of the following attributes:

    ATTRIBUTE TYPEATTRIBUTE VALUE

    Interface StabilityStandard

    MT-Level

     

    SEE ALSO

    drand48(3C), attributes(5), standards(5)


     

    Index

    NAME
    SYNOPSIS
    DESCRIPTION
    USAGE
    ATTRIBUTES
    SEE ALSO


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