Dear all, I have come across some peculiar behaviour using $RANDOM in some shell scripts (in this case, to generate different random serial numbers for testing).
It is best explained by example. I have attached 3 shell scripts that illustrate the behaviour: * busybox_test_random_v1.sh uses $RANDOM in a function, where the function is called several times * busybox_test_random_v2.sh uses $RANDOM in several different functions, where the functions are called once each (but do the same thing) * busybox_test_random_v3.sh uses $RANDOM only in the body of the script. In _v1.sh and _v2.sh, the **same string** of numbers is generated when calls to the function are repeated, whereas v3 behaves as expected - each random string of digits are different. It's as though the random number is re-seeded with the same seed each time one of those functions are called. For example, when running v1, I get: unitnumber 967232 articlenumber 967232 <- Same as above coreboard 9672324689 <- 10 digits instead of 6, but still the same hardwarerelease 967232 <- Same 6 digits as above when running _v2: unitnumber 818769 articlenumber 818769 coreboard 8187697396 hardwarerelease 818769 <- Same sequence of digits And _v3: unitnumber 490963 articlenumber 357642 coreboard 3285917950 hardwarerelease 577456 <- All different, as desired. Running the same scripts on bash (dash not tried) in Ubuntu 9.10 does not exhibit the same behaviour. That is: >From v1: unitnumber 260060 articlenumber 967509 coreboard 8451689963 hardwarerelease 542427 <- All different, as desired >From v2: unitnumber 481551 articlenumber 169890 coreboard 0564598440 hardwarerelease 733998 <- All different, as desired >From v3: unitnumber 470484 articlenumber 256473 coreboard 5805465281 hardwarerelease 032857 <- All different, as desired I have attached the scripts used to test these functions. We have built busybox for an MPC5151 (PowerPC embedded device) using DENX ppc_6xx- for the following version: Version: BusyBox v1.14.1 (2009-08-10 12:28:49 EST) multi-call binary Copyright (C) 1998-2008 Erik Andersen, Rob Landley, Denys Vlasenko and others. Licensed under GPLv2. See source distribution for full notice. Best regards Damien Dusha.
busybox_run_test.sh
Description: Bourne shell script
busybox_test_random_v1.sh
Description: Bourne shell script
busybox_test_random_v2.sh
Description: Bourne shell script
busybox_test_random_v3.sh
Description: Bourne shell script
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