arc4random - Linux
Overview
The arc4random
command is a secure and high-quality pseudorandom number generator (PRNG) built into macOS and Linux. It’s a portable implementation of the popular ARC4 cipher, known for its speed, unpredictability, and suitability for cryptographic applications.
Syntax
arc4random
Options/Flags
No options are available.
Examples
Generate a random integer:
$ arc4random
1234567890
Generate a range of integers:
$ for i in $(arc4random % 100); do echo $i; done
97
34
55
...
Generate a random character:
$ echo $(arc4random | od -An -t u1 1)
Common Issues
- Secure usage:
arc4random
is a pseudorandom generator, not a true random generator. It should not be used for critical security applications where genuine randomness is essential. - Seeding: The initial seed for
arc4random
is derived from the system’s entropy pool. If the pool is weak, the generated numbers may be less random.
Integration
- Use with other commands to create complex random sequences:
$ seq 1 10 | xargs arc4random -o
1234567890
Related Commands
- random: Another built-in PRNG in macOS and Linux.
- urandom: Linux pseudorandom generator that uses kernel entropy.
- /dev/random: Linux device for generating truly random numbers (slow).