LinuxQuestions.org
Latest LQ Deal: Complete CCNA, CCNP & Red Hat Certification Training Bundle
Go Back   LinuxQuestions.org > Forums > Linux Forums > Linux - Newbie
User Name
Password
Linux - Newbie This Linux forum is for members that are new to Linux.
Just starting out and have a question? If it is not in the man pages or the how-to's this is the place!

Notices


Reply
  Search this Thread
Old 10-29-2004, 12:58 AM   #1
kimchee411
Member
 
Registered: Sep 2004
Posts: 30

Rep: Reputation: 15
Where to download commands not included with my distro?


I'm trying to find the unix "random" command that generates a random number, but it's hard to do a search for. Anyone know where I can find this and other simple commands, like "calendar"? I'm using FC2 if it matters. Thx.
 
Old 10-29-2004, 01:21 AM   #2
sephiro499
Member
 
Registered: Sep 2003
Location: Baltimore, MD
Distribution: Fedora Core 8
Posts: 39

Rep: Reputation: 15
If your distro supports RPM installer files you might want to take a look at http://rpmfind.net/linux/RPM/
 
Old 10-29-2004, 01:26 AM   #3
masand
LQ Guru
 
Registered: May 2003
Location: INDIA
Distribution: Ubuntu, Solaris,CentOS
Posts: 5,522

Rep: Reputation: 58
hi
try this

[root@gaurav root]# man random

or to look at other pages having random in their content

[root@gaurav root]# apropos random

will help u

regards
 
Old 10-29-2004, 01:45 AM   #4
kimchee411
Member
 
Registered: Sep 2004
Posts: 30

Original Poster
Rep: Reputation: 15
Quote:
Originally posted by masand
hi
try this

[root@gaurav root]# man random

or to look at other pages having random in their content

[root@gaurav root]# apropos random

will help u

regards
I don't understand how rand(), random(), srand(), etc... works. If you know, can you explain it to me? I'm just trying to simulate a die roll for a csh craps script I'm writing for class. it would be a lot easier if I could just find the "random" command, which is very simple and straight fwd.
 
Old 10-29-2004, 05:31 AM   #5
dalek
Senior Member
 
Registered: Jul 2003
Location: Mississippi USA
Distribution: Gentoo
Posts: 2,058
Blog Entries: 2

Rep: Reputation: 79
man random:

Quote:
RANDOM

Section: Linux Programmer's Manual (3 )

NAME


random, srandom, initstate, setstate - random number generator

SYNOPSIS


#include <stdlib.h>

long int random(void);
void srandom(unsigned int seed);
char *initstate(unsigned int seed, char *state, size_t n);
char *setstate(char *state);



DESCRIPTION


The random() function uses a non-linear additive feedback random number generator employing a default table of size 31 long integers to return successive pseudo-random numbers in the range from 0 to RAND_MAX. The period of this random number generator is very large, approximately 16*((2**31)-1).

The srandom() function sets its argument as the seed for a new sequence of pseudo-random integers to be returned by random(). These sequences are repeatable by calling srandom() with the same seed value. If no seed value is provided, the random() function is automatically seeded with a value of 1.

The initstate() function allows a state array state to be initialized for use by random(). The size of the state array n is used by initstate() to decide how sophisticated a random number generator it should use - the larger the state array, the better the random numbers will be. seed is the seed for the initialization, which specifies a starting point for the random number sequence, and provides for restarting at the same point.

The setstate() function changes the state array used by the random() function. The state array state is used for random number generation until the next call to initstate() or setstate(). state must first have been initialized using initstate () or be the result of a previous call of setstate().

RETURN VALUE


The random() function returns a value between 0 and RAND_MAX. The srandom() function returns no value. The initstate() and setstate() functions return a pointer to the previous state array, or NULL on error.

ERRORS




EINVAL
A state array of less than 8 bytes was specified to initstate().

NOTES


Current "optimal" values for the size of the state array n are 8, 32, 64, 128, and 256 bytes; other amounts will be rounded down to the nearest known amount. Using less than 8 bytes will cause an error.

CONFORMING TO


BSD 4.3

SEE ALSO


rand(3), srand(3)
man rand:

Quote:
RAND

Section: Linux Programmer's Manual (3)

NAME

rand, rand_r, srand - pseudo-random number generator

SYNOPSIS

#include <stdlib.h>

int rand(void);

int rand_r(unsigned int *seedp);

void srand(unsigned int seed);


DESCRIPTION

The rand() function returns a pseudo-random integer between 0 and RAND_MAX.

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

If no seed value is provided, the rand() function is automatically seeded with a value of 1.

The function rand() is not reentrant or thread-safe, since it uses hidden state that is modified on each call. This might just be the seed value to be used by the next call, or it might be something more elaborate. In order to get reproducible behaviour in a threaded application, this state must be made explicit. The function rand_r() is supplied with a pointer to an unsigned int, to be used as state. This is a very small amount of state, so this function will be a weak pseudo-random generator. Try drand48_r(3) instead.

RETURN VALUE

The rand() and rand_r() functions return a value between 0 and RAND_MAX. The srand() function returns no value.

EXAMPLE

POSIX 1003.1-2003 gives the following example of an implementation of rand() and srand(), possibly useful when one needs the same sequence on two different machines.


static unsigned long next = 1;

/* RAND_MAX assumed to be 32767 */
int myrand(void) {
next = next * 1103515245 + 12345;
return((unsigned)(next/65536) % 32768);
}

void mysrand(unsigned seed) {
next = seed;
}



NOTES

The versions of rand() and srand() in the Linux C Library use the same random number generator as random() and srandom(), so the lower-order bits should be as random as the higher-order bits. However, on older rand() implementations, and on current implementations on different systems, the lower-order bits are much less random than the higher-order bits. Do not use this function in applications intended to be portable when good randomness is needed.

FreeBSD adds a function

void sranddev(void);

that initializes the seed for their bad random generator rand() with a value obtained from their good random generator random(). Strange.

In Numerical Recipes in C: The Art of Scientific Computing (William H. Press, Brian P. Flannery, Saul A. Teukolsky, William T. Vetterling; New York: Cambridge University Press, 1992 (2nd ed., p. 277)), the following comments are made:
"If you want to generate a random integer between 1 and 10, you should always do it by using high-order bits, as in


j=1+(int) (10.0*rand()/(RAND_MAX+1.0));


and never by anything resembling


j=1+(rand() % 10);


(which uses lower-order bits)."


Random-number generation is a complex topic. The Numerical Recipes in C book (see reference above) provides an excellent discussion of practical random-number generation issues in Chapter 7 (Random Numbers).

For a more theoretical discussion which also covers many practical issues in depth, please see Chapter 3 (Random Numbers) in Donald E. Knuth's The Art of Computer Programming, volume 2 (Seminumerical Algorithms), 2nd ed.; Reading, Massachusetts: Addison-Wesley Publishing Company, 1981.
man srand

Quote:
RAND

Section: Linux Programmer's Manual (3)

NAME

rand, rand_r, srand - pseudo-random number generator

SYNOPSIS

#include <stdlib.h>

int rand(void);

int rand_r(unsigned int *seedp);

void srand(unsigned int seed);


DESCRIPTION

The rand() function returns a pseudo-random integer between 0 and RAND_MAX.

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

If no seed value is provided, the rand() function is automatically seeded with a value of 1.

The function rand() is not reentrant or thread-safe, since it uses hidden state that is modified on each call. This might just be the seed value to be used by the next call, or it might be something more elaborate. In order to get reproducible behaviour in a threaded application, this state must be made explicit. The function rand_r() is supplied with a pointer to an unsigned int, to be used as state. This is a very small amount of state, so this function will be a weak pseudo-random generator. Try drand48_r(3) instead.

RETURN VALUE

The rand() and rand_r() functions return a value between 0 and RAND_MAX. The srand() function returns no value.

EXAMPLE

POSIX 1003.1-2003 gives the following example of an implementation of rand() and srand(), possibly useful when one needs the same sequence on two different machines.


static unsigned long next = 1;

/* RAND_MAX assumed to be 32767 */
int myrand(void) {
next = next * 1103515245 + 12345;
return((unsigned)(next/65536) % 32768);
}

void mysrand(unsigned seed) {
next = seed;
}



NOTES

The versions of rand() and srand() in the Linux C Library use the same random number generator as random() and srandom(), so the lower-order bits should be as random as the higher-order bits. However, on older rand() implementations, and on current implementations on different systems, the lower-order bits are much less random than the higher-order bits. Do not use this function in applications intended to be portable when good randomness is needed.

FreeBSD adds a function

void sranddev(void);

that initializes the seed for their bad random generator rand() with a value obtained from their good random generator random(). Strange.

In Numerical Recipes in C: The Art of Scientific Computing (William H. Press, Brian P. Flannery, Saul A. Teukolsky, William T. Vetterling; New York: Cambridge University Press, 1992 (2nd ed., p. 277)), the following comments are made:
"If you want to generate a random integer between 1 and 10, you should always do it by using high-order bits, as in


j=1+(int) (10.0*rand()/(RAND_MAX+1.0));


and never by anything resembling


j=1+(rand() % 10);


(which uses lower-order bits)."


Random-number generation is a complex topic. The Numerical Recipes in C book (see reference above) provides an excellent discussion of practical random-number generation issues in Chapter 7 (Random Numbers).

For a more theoretical discussion which also covers many practical issues in depth, please see Chapter 3 (Random Numbers) in Donald E. Knuth's The Art of Computer Programming, volume 2 (Seminumerical Algorithms), 2nd ed.; Reading, Massachusetts: Addison-Wesley Publishing Company, 1981.
That help any?? I have never used it but that is the man pages.

Later



Biggest post I ever made.
 
Old 10-29-2004, 08:29 AM   #6
DertyolBA$HTARD
Member
 
Registered: Sep 2004
Location: USA
Distribution: Slackware 10
Posts: 86

Rep: Reputation: 15
rpm -q <command>

queries the rpm database for the specified command. That lets you know if it is installed.

As far as downloading rpm I go to sourceforge.net or rpmfind.net
 
Old 10-29-2004, 08:48 AM   #7
jschiwal
LQ Guru
 
Registered: Aug 2001
Location: Fargo, ND
Distribution: SuSE AMD64
Posts: 15,733

Rep: Reputation: 670Reputation: 670Reputation: 670Reputation: 670Reputation: 670Reputation: 670
You can get a random number by using the environmental variable $RANDOM.
At least in bash. Also, there is a /dev/random device. If a computer has a hardware random number generator, then look for dev/hw_random.
 
Old 10-29-2004, 01:12 PM   #8
blueplazma
Member
 
Registered: Jun 2002
Distribution: Debian/Ubuntu
Posts: 56

Rep: Reputation: 15
/dev/random would be my recommendation. And if by calendar you just mean the date, try the "date" command. If you mean more like a full-fledged calendar/schedule program, try Evolution.
 
Old 10-30-2004, 07:49 AM   #9
DertyolBA$HTARD
Member
 
Registered: Sep 2004
Location: USA
Distribution: Slackware 10
Posts: 86

Rep: Reputation: 15
Or "cal" at a bash prompt, at least on slackware 10
 
  


Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off



Similar Threads
Thread Thread Starter Forum Replies Last Post
where is the source code for utilities in a distro? (If they are included) dr_zayus69 Linux - Software 1 09-04-2005 11:45 AM
from where 2 download commands fhameed Linux - Software 2 09-03-2004 11:17 AM
What distro has all these included? kromatic Linux - General 2 07-17-2004 06:42 PM
mgetty included in distro slack66 Linux - Newbie 1 08-12-2003 05:24 AM
Which Distro Comes with PPTP included? friendklay Linux - Networking 1 01-22-2003 05:43 PM


All times are GMT -5. The time now is 05:35 PM.

Main Menu
Advertisement
My LQ
Write for LQ
LinuxQuestions.org is looking for people interested in writing Editorials, Articles, Reviews, and more. If you'd like to contribute content, let us know.
Main Menu
Syndicate
RSS1  Latest Threads
RSS1  LQ News
Twitter: @linuxquestions
Facebook: linuxquestions Google+: linuxquestions
Open Source Consulting | Domain Registration