bash uuid generator
Onliner bash scripts are handy but bash and common utilities don’t always work the same on the two systems I most use: Centos vs. OS X.
centos $ cat /etc/redhat-release
CentOS release 5.4 (Final)
osx $ sw_vers | head -n2
ProductName: Mac OS X
ProductVersion: 10.6.2
For example, I recently wrote a simple script to generate a set of UUID using the uuidgen utility. OS X and Centos versions of uuidgen take very different parameters.
Of course they do.
Centos uuid manpage
UUIDGEN(1) UUIDGEN(1)
NAME
uuidgen - command-line utility to create a new UUID value
SYNOPSIS
uuidgen [ -r | -t ]
...
I like to use the uuidgen -r option to explicitly generate a random-based UUID. It’s not strictly necessary as this is the default behavior. Still, I like to put it in. That’s just me. OS X doesn’t have this option. Oh, well.
OS X uuidgen manpage
UUIDGEN(1) BSD General Commands Manual UUIDGEN(1)
NAME
uuidgen -- generates new UUID strings
SYNOPSIS
uuidgen [-hdr]
...
Next up, OS X generates UUID in upper case whereas Centos generates UUID in lower case.
centos $ uuidgen
18722f8e-14cd-41fb-a63e-af9ff1c287ce
osx $ uuidgen
81AE9EAC-0B8B-4DB9-B262-76AA8C285DD6
Again, not really a big deal but I like consistency. Easy to fix with a pipe and tr.
osx $ uuidgen | tr [:upper:] [:lower:]
62a4d6b9-e0a9-4996-9e71-e7291158b700
But I needed a set of UUID. A simple loop would suffice.
centos $ for i in `seq 1 4`; do uuidgen | tr [:upper:] [:lower:]; done
408bf1d7-80a6-41ee-8a75-f7bbb5b65dd7
ae5e0aa4-f0b2-48ff-9cfe-ab99fb37b5c7
7e0a7e69-364d-4259-9b3f-83d448e9b591
e1d1b257-974e-4754-a6d3-fe4566b55c93
osx $ for i in `seq 1 4`; do uuidgen | tr [:upper:] [:lower:]; done
-bash: seq: command not found
Drat! No `seq 1 4` in OS X.
Okay. Use the alternate form to declare a sequence.
osx $ for i in {1..4}; do uuidgen | tr [:upper:] [:lower:]; done
c861326b-bde8-4198-b45a-6bfb7016addb
ef813568-5d3d-4587-a170-8aab798fd83b
21fe8562-1511-4fd4-bd37-71b43c32e013
acb10051-9af8-42b8-9ac9-54010ad71d07
and verifiy that it also works on Centos.
centos $ for i in {1..4}; do uuidgen | tr [:upper:] [:lower:]; done
93c68aba-cbe5-4b79-a1cc-e00eaae0527a
c564a4f4-9d39-4d2d-8762-4ba506c97de8
f694000b-d2cc-4b31-aabd-c3facd13b081
86466e00-3948-45f7-9090-09ab816b8fb6
Would ruby be easier? Probably not for this simple hack.
If I knew ruby better, dropping into irb would be just as easy as bash oneliners. But there would be other problems. For example, “Which ruby?”
centos $ ruby -v
ruby 1.9.1p376 (2009-12-07 revision 26041) [x86_64-linux]
osx $ ruby -v
ruby 1.8.7 (2008-08-11 patchlevel 72) [universal-darwin10.0]
2 Comments:
It’s been said many times before and I’ll say it here:
OS X ain’t linux
True. Then again, linux ain’t linux. (hint: debian vs. centos)
I’ll happily live with the bsd and linux differences over the windows alternative.
kelly
20:28
FYI, Apple’s ‘uuidgen’ utility is out of compliance with the UUID specification. The spec says:
• UUID hex strings should be generated (output) in lowercase.
• Uppercase hex strings should be tolerated as input.
The spec’s actual language is quite clear:
—
6.5.4 Software generating the hexadecimal representation of a UUID shall not use upper case letters. NOTE – It is recommended that the hexadecimal representation used in all human-readable formats be restricted to lower-case letters. Software processing this representation is, however, required to accept both upper and lower case letters as specified in 6.5.2.
—
UUID spec: http://www.itu.int/rec/T-REC-X.667/en
Note that some UUID utilities from Microsoft generated UUID (GUID) hex strings in mixed case, apparently a programming error by the MS staff.
Thanks for sharing your bash code to fix this Apple (BSD?) problem.
Basil
14:25