Bash programming RANDOM does not work General Help Question

Question Bash programming RANDOM does not work ( Ubuntu Forums General Help )
Updated: 2008-11-23 01:55:09 (9)

Bash programming RANDOM does not work

This bit of code is supposed to produce a series of random numbers.... it doesn't (for me!). A tip on what I am doing wrong? (Is my bash broke?) Thanks!

Code:

#!/bin/bash
count=0;     # initialize x to 0
RANDOM=$$$(date +%s)

echo $RANDOM
while [ "$count" -le 10 ]; do
    number=$RANDOM
    echo "Current value of count: $count: $number"
    # increment the value of count:
    count=$(expr $count + 1)
    sleep 1
done

Answers: Bash programming RANDOM does not work ( Ubuntu Forums General Help )

Bash programming RANDOM does not work

Try this to see if it works on your computer.

Code:

#!/bin/bash
# This is a bash script to create a fourteen character string of random numeric digits.
echo -n "The random number is "
for ((i=1; i<15; i++)) ; do
echo -n $(( $RANDOM / 3276 ))
done
echo

454redhawk

Bash programming RANDOM does not work

Quote:

Originally Posted by 454redhawk

Try this to see if it works on your computer.

Code:

#!/bin/bash
# This is a bash script to create a fourteen character string of random numeric digits.
echo -n "The random number is "
for ((i=1; i<15; i++)) ; do
echo -n $(( $RANDOM / 3276 ))
done
echo

I get an error with your code: The random number is random_rename.bsh: 9: Syntax error: Bad for loop variable

Can't seem to get your for loop working, but that is not really the problem. When I put echo -n $(( $RANDOM / 3276 )) in my loop, I get the same unfortunate non-random results. Curious!

I got -301431-301431-301431-301431-301431-301431-301431-301431-301431-301431-301431

here is my loop with your echo:

Code:

#!/bin/bash
count=0;     # initialize count to 0
RANDOM=$$$(date +%s)
echo $RANDOM
while [ "$count" -le 10 ]; do #start of loop
    echo -n $(( $RANDOM / 3276 ))
    #echo "Current value of count: $count: $number"
    # increment the value of count:
    count=$(expr $count + 1)
    sleep 1
done

wgw

Bash programming RANDOM does not work

From the man page.

Its worth a try

Code:

CONFIGURING
       If your system does not have /dev/random and /dev/urandom created already, they can  be  cre-
       ated with the following commands:

               mknod -m 644 /dev/random c 1 8
               mknod -m 644 /dev/urandom c 1 9
               chown root:root /dev/random /dev/urandom

454redhawk

Bash programming RANDOM does not work

The problem is because you redefine the name "RANDOM". Also instead of the deprecated "$(expr $count + 1)" you should use "((count++))".

Code:

# Maybe you want something like this?
for ((i=1;i<11;i++)); do
    printf "\rcurrent value of count: $i: $RANDOM"
    sleep 0.2
done; echo

# Here's an example of to how increment a variable:
count=1; for i in {1..10}; do
    printf "\r$count"
    ((count++))
    sleep 0.2
done; echo

# Or increment in a printf command:
count=1; for i in {1..10}; do
    printf "\r$((count++))"
    sleep 0.2
done; echo

bashologist

Bash programming RANDOM does not work

Well, here is my (noobie) problem: I was issuing the command as: sh test.bsh.

Why? God only knows (actually I think it would be a mystery to Him as well...) I think it is because I tried the file name at the command line and it didn't work; then I tried sh filename and it did, sort of. So I continued with sh....

However, ./filename works.

Sorry to have troubled you. Your loop works fine as well.

(In the future, I will include my command line as well -- would have resolved the question right away. )

wgw

Bash programming RANDOM does not work

I just tested this and I get the same result.

If I make the first line of the script read

Code:

#!/bin/sh

then it acts differently to having

Code:

#!/bin/bash

Note that ./scriptname causes the script to execute by means of the interpreter indicated on the first line. The command "sh scriptname" causes the script to be executed by "sh" as interpreted, irrespective of what is specified as interpreter in the first line of the script.

In this light, you can also test this syntax:

Code:

bash scriptname

This is interesting in the light of /bin/sh -> /bin/bash... These two files are basically for all practical purposes one-and-the-same. /bin/sh points to /bin/bash.

Strange, but probably defined and documented behavior somewhere in the annals. (There are many instances of Unix/Linux commands behaving differently depending on which "name" you used to call them)

hartz

Bash programming RANDOM does not work

Quote:

Originally Posted by hartz3

This is interesting in the light of /bin/sh -> /bin/bash... These two files are basically for all practical purposes one-and-the-same. /bin/sh points to /bin/bash.

S 1f40 trange, but probably defined and documented behavior somewhere in the annals. (There are many instances of Unix/Linux commands behaving differently depending on which "name" you used to call them)

Since Edgy, /bin/sh points to Dash, not Bash

mcduck

Bash programming RANDOM does not work

It doesn't in my fresh install of xubuntu 7.04, not in my upgraded over-and-over-since 6.04 Ubuntu.

I seem to recall seeing a note about this previously though...

hartz

Bash programming RANDOM does not work

Quote:

Originally Posted by hartz3

It doesn't in my fresh install of xubuntu 7.04, not in my upgraded over-and-over-since 6.04 Ubuntu.

I seem to recall seeing a note about this previously though...

Well, it should point to dash

Code:

$ ls -la /bin | grep sh
-rwxr-xr-x  1 root root  700560 2007-04-11 01:32 bash
-rwxr-xr-x  1 root root   80500 2007-03-05 07:00 dash
lrwxrwxrwx  1 root root       4 2007-04-21 17:31 rbash -> bash
lrwxrwxrwx  1 root root       4 2006-11-12 18:05 sh -> dash
lrwxrwxrwx  1 root root       4 2007-04-21 17:31 sh.distrib -> bash

mcduck

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