Generate random string linux

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Others options not necessarily related: uuidgen

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How to Generate a Random String in Linux?

A random string is a sequence of characters that is generated using a random process or algorithm, without any specific pattern or structure. It ensures that the string is unique and not easily found by an attacker. It has various uses in Linux, such as generating passwords, creating unique identifiers or tokens, and testing software applications.

This guide will illustrate several methods to generate a random string in Linux:

• Method 1: Using the Random Number Generator (RNG)
• Method 2: Using the OpenSSL Library
• Method 3: Using the UUID Generator
• Method 4: Using the mktemp Command

Method 1: Using the Random Number Generator (RNG)

The “RNG” is a kernel-level device that generates random numbers by collecting entropy from various sources, such as hardware interrupts, mouse movement, and keyboard input. Use the “tr” command to translate these random numbers into a random string. Here’s an example:

The command “cat /dev/urandom | tr -dc ‘a-zA-Z0-9’ | fold -w 10 | head -n 1” is a one-line Linux command that generates a random alphanumeric string of 10 characters. The description of this command is mentioned below:

• cat /dev/urandom: reads random bytes from the Linux kernel’s random number generator device “/dev/urandom”.
• “tr -dc ‘a-zA-Z0-9’: deletes any characters that are not alphanumeric (letters or digits) in the input stream.
• “fold -w 10“: formats the output stream into lines of 10 characters each. This creates a string of 10 characters.
• “head -n 1“: selects only the first line of output from “fold -w 10”.

The script is written below:

$ cat /dev/urandom | tr -dc 'a-zA-Z0-9' | fold -w 10 | head -n 1

This command generates a random string of 10 characters using the RNG.

Method 2: Using the OpenSSL Library

The OpenSSL library provides a random number generator that is used to generate random strings. The “openssl rand” command generates a sequence of random bytes.

An example with a brief description is provided below:

• “openssl rand”: command-line tool for generating random data using OpenSSL’s cryptographic functions.
• “-base64”: tells OpenSSL to encode the random data in base64 format (binary-to-text encoding scheme).
• “10”: specifies the number of random bytes to generate.

It generates a random sequence of bytes which is encoded in base64 format using the OpenSSL library.

Method 3: Using the UUID Generator

The UUID generator is a tool that generates universally unique identifiers (UUIDs). UUIDs are 128-bit values that can be used to generate random strings. Here’s an example:

An example is considered to generate the random string using the “UUID” generator. The description of the command is provided below:

• “tr -dc ‘a-zA-Z0-9’” command deletes characters that are not letters or digits in the input stream.
• “fold -w 10” formats the output stream into lines of 10 characters each. It creates a string of 10 characters.
• “head -n 1” command selects only the first line of output.

$ uuidgen | tr -dc 'a-zA-Z0-9' | fold -w 10 | head -n 1

This command generates a random string of 10 characters using the UUID generator.

Method 4: Using the mktemp Command

The “mktemp” command is utilized to create temporary files and directories. It can also be utilized to generate random strings. The description of the below command is given below:

• mktemp: command stands for “make temporary”.
• u: option tells it to only print the name of the file or directory that it creates, without actually creating it.
• XXXXXXXXXX: represents a sequence of ten X’s, which are replaced by mktemp with a random string of characters to create a unique filename.

An example is carried out to generate the random string. For instance, specify the “XXXXXXXXXX” to create a unique filename:

The output shows a random string of 10 characters via the mktemp command.

Conclusion

To generate a random string in Linux, use the “Random Number Generator”, “OpenSSL library”, “UUID generator”, and “mktemp” commands. The generated random string makes it difficult for an attacker to gain unauthorized access to a system or data.

This tutorial has demonstrated several methods to generate a random string in Linux.

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Generate Random String in Bash

Bash provides a built-in variable $RANDOM that generates random numbers between 0 and 32767 . We can use this variable to generate random strings of any length. Here’s how to generate a random string of length 10 . The above code’s working is as follows:

• echo "$RANDOM" | md5sum generates a 32-character MD5 hash from the $RANDOM variable.
• printf '%s' converts the hash to a string.
• cut -c 1-10 selects the hash’s first 10 characters. And the echo command displays output on the console.

Use /dev/urandom Command

Use the /dev/urandom command to generate a random string in Bash.

The above code’s working is as follows:

• The tr -dc 'a-zA-Z0-9' command filters the output of /dev/urandom to include only alphanumeric characters, i.e., letters (both uppercase and lowercase) and digits.
• The fold -w 10 command wraps the output of tr after every 10 characters, creating a new line for each 10-character segment.
• Finally, the head -n 1 command selects the first line of the output, which contains the randomly generated string of 10 characters.

Using openssl Command

Use the openssl command to generate a random string in Bash.

The above code’s working is as follows:

• The openssl rand command generates random data.
• The -base64 encodes the generated data in Base64 format.
• And 15 specifies the number of bytes to generate, which translates 10 characters in Base64 format.

Further reading:

Check if String starts with another String in Bash

Get random number between 1 and 100 in Bash

Using uuid Command

Use uuid to generate a random string in Bash.

The above code’s working is as follows:

• The cat /proc/sys/kernel/random/uuid command generates a random UUID (Universally Unique Identifier) using the kernel’s random number generator and outputs it to the console.
• This part | sed 's/[-]//g' of the command pipes the previous command’s output to the sed command, which searches for any hyphens in the output and replaces them with nothing (i.e., removes them). The g flag means to do this globally (i.e., for all occurrences of hyphens in the output).
• This part | head -c 20 of the command pipes the output of the sed command to the head command, which takes the output’s first 20 characters and prints them to the console.
• And ; echo prints a newline character to the console after the random string

Conclusion

Considering the above solutions, we have explored four different methods to generate random strings in Bash. These methods include using the $Random , /dev/urandom , openssl , and uuid commands. You can choose the method that best suits your needs. Using these methods, you can generate random strings for various applications, such as password generation and token authentication.

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