How to Generate Random Numbers in Linux Shell Scripting with an index

 There could be situations wherein you need to create random number or a random file name or a random password. Lets do it through a shell script. 

To generate a random number in a UNIX or Linux shell, the shell called a shell variable named RANDOM. Each time this variable is called, a random number between 0 and 32767 is generated.

The RANDOM variable should be initialized  to an initial value (ike the process ID of the current shell, which is maintained by the variable $$.

Example 1: 

Lets check how we generate 10 random numbers. 

Script:

generate 10 random numbers

Output: Make the script executable and then run the script.

[root@devopszones ~]#chmod +x 10-random-numbers.sh
[root@devopszones ~]#
[root@devopszones ~]#
[root@devopszones ~]#./10-random-numbers.sh
14499
24829
17111
28602
9732
22096
21859
31971
14950
4219
[root@devopszones ~]#

Example 2: Let Generate as many as random numbers you want

We will generate as many as random numbers we want by giving a positional argument while executing the script.

Script:

with Positional argument

Output: Make the script executable and then run the script.

[root@devopszones ~]#chmod +x random_generate_with_positional_arg.sh
[root@devopszones ~]#
[root@devopszones ~]#
[root@devopszones ~]#./random_generate_with_positional_arg.sh 12
4325
14709
14637
25770
176
18926
15211
9889
18253
11598
31544
14930
23961
[root@devopszones ~]#

Example 3: Let Generate as many as random numbers you want with an Index

We will generate as many as random numbers we want by giving a positional argument while executing the script. It will add an index to it.

Script:

positional argument with index

Output: Make the script executable and then run the script.

[root@devopszones ~]#chmod +x random_generate_with_positional_arg_index.sh
[root@devopszones ~]#./random_generate_with_positional_arg_index.sh 13
0 27576
1 3467
2 10018
3 12771
4 14833
5 32188
6 24743
7 10792
8 26533
9 28763
10 13392
11 13133
12 24793
13 23472
[root@devopszones ~]#

Example 4: Let Generate as many as random numbers you want with an Index and with a default value for Positional argument.

We will generate as many as random numbers we want by giving a positional argument while executing the script. It will add an index to it. If we do not provide an positional argument to the script it'll take 10 as default value.

Script:

Positional Argument with default Value

Output: Make the script executable and then run the script.

[root@devopszones ~]#chmod +x random_num_sec_example_default.sh
[root@devopszones ~]#
[root@devopszones ~]#
[root@devopszones ~]#
[root@devopszones ~]#./random_num_sec_example_default.sh
0 28281
1 19562
2 24905
3 5437
4 2123
5 10329
6 7947
7 7441
8 28206
9 15030
10 9124
[root@devopszones ~]#./random_num_sec_example_default.sh 14
0 20047
1 9996
2 2719
3 22236
4 7134
5 14774
6 31742
7 24772
8 9092
9 13406
10 13866
11 15672
12 17290
13 16315
14 3968
[root@devopszones ~]#

Example 5: Let Generate as many as random numbers you want with an Index and with a default value for Positional argument. Send the Generated value to a file.

We will generate as many as random numbers we want by giving a positional argument while executing the script. It will add an index to it. If we do not provide an positional argument to the script it'll take 10 as default value. As a final nail in the coffin it'll send the output to a file.

Script:

Positional Argument with default Value. Send Output to a file

Output: Make the script executable and then run the script.

[root@devopszones ~]#chmod +x random_num_sec_example.sh
[root@devopszones ~]#./random_num_sec_example.sh 15
[root@devopszones ~]#cat inputfile3
0 6749
1 21349
2 17039
3 30703
4 593
5 11085
6 26653
7 26761
8 13332
9 3551
10 26855
11 19697
12 32595
13 25168
14 12581
15 31042
[root@devopszones ~]#