srand()

Start a new sequence of pseudo-random integers

Synopsis:

#include <stdlib.h>

void srand( unsigned int seed );

Arguments:

seed: The seed of the sequence of pseudo-random integers.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The srand() function uses the argument seed to start a new sequence of pseudo-random integers to be returned by subsequent calls to rand(). A particular sequence of pseudo-random integers can be repeated by calling srand() with the same seed value. The default sequence of pseudo-random integers is selected with a seed value of 1.

Examples:

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

int main( void )
  {
    int i;

    srand( 982 );
    for( i = 1; i < 10; ++i ) {
      printf( "%d\n", rand() );
    }

    /* Start the same sequence over again. */

    srand( 982 );
    for( i = 1; i < 10; ++i ) {
      printf( "%d\n", rand() );
    }

    /*
     Use the current time as a seed to
     get a different sequence.
    */

    srand( (int) time( NULL ) );
    for( i = 1; i < 10; ++i ) {
      printf( "%d\n", rand() );
    }

    return EXIT_SUCCESS;
  }

Classification:

ANSI, POSIX 1003.1

Safety:
Cancellation point	No
Interrupt handler	No
Signal handler	Yes
Thread	Yes