Hi There!
Apologies if this has been asked previously but I couldn't find the answer I was hoping for.
Basically, all I want to do is compare the OS X version against the version that I require in my script. So I'm retrieving the OS version using defaults read, but how can I compare this against another version number to see which is the greatest / newest?
Many thanks in advance...
davewg
You have to know ahead of time or lookup what the newest version is: off the net with maybe wget or from a file.. The OS does not know anything about what the newest version is.
I really do not understand what you are doing. If you are deploying something that requires version c of the OS (or some utility) on a box running version a, what do you intend to do in your code?
Code like that should abend with an error message complaining about versions, in the worst case.
A more user-friendly approach is to do what sysconf() does - learn about the system, then call code which is friendly to the environment. Find a way not to have to issue a nasty message. Especially if you want users to actually use the code.
Maybe it's in case software is running in a NFS mounted system on different systems.
Say you have AIX, you could capture the output of "oslevel" and run a test against it in the script. Actually probably better to use "uname -a" for portability.
It's just for a script in an installer package that needs to check the OS version to ensure it's suitable.
So I have for example decided that 10.4.6 is the required version my install needs and a variable with that value is already set in my script. Then, my script runs and detects that the OS X version of the target is 10.4.11. All I need to do now is to compare them, and then I can return the appropriate result to the installer...
Oh. details like that help a lot.
One way to do this try this for starters-
#!/bin/ksh
# input versionstring1 versionstring2 example: 10.10.1 10.8.3
# returns 0 if string1 = string2
# <0 if string1 < string2
# >0 if string1 > string2
# this assumes xx.xx.xx for version number
vercmp()
{
IFS=.
echo "$1" | read a1 b1 c1
echo "$2" | read a2 b2 c2
IFS=" "
r1=$((a1 - a2))
r2=$((b1 - b2))
r3=$((c1 - c2))
tot=$((r1 + r2 + r3))
if [ $tot -eq 0 ] ; then
print 0
return 0
fi
if [[ $r1 -gt 0 || $r2 -gt 0 || $r3 -gt 0 ]] ; then # changed
print 1
return 0
fi
retval="-1" # changed
echo "$retval" # changed
}
#usage:
if [ $(vercmp 10.10.1 10.2.4) -gt -1 ] ; then
echo "version okay"
else
echo "version too old"
fi
Apologies I should of been more clear in my post but thank you for your response.
I tried running the example code, but unforunately some errors were returned in Terminal (terminal shell set to /bin/ksh);
/Scripts/check[21]: [: ']' missing
/Scripts/check[21]: 8: not found [No such file or directory]
/Scripts/check[21]: -3: not found [No such file or directory]
/Scripts/check[25]: print: -1: unknown option
Usage: print [-enprs] [-f format] [-u fd] [string ...]
/Scripts/check[30]: [: argument expected
version too old
any ideas what the problem could be?
my bad - see the lines highlighted in red
That works a treat! thank you for your help 
I should just point out that whilst this comparison works ok in Leopard (10.5.6), on Tiger (10.4.11) it always returns success regardless of the numbers it is comparing. 
I'm not familiar with OS X, but usually version numbers are weighted. That may be the reason for the unrespected results on Tiger.
A script assuming max. 3 digits for any number could look like this:
#!/bin/ksh
# compare version numbers
# usage: vercmp <versionnr1> <versionnr2>
# with format for versions xxx.xxx.xxx
# returns: 0 if versionnr1 equal or greater
# 1 if versionnr1 lower
vercmp()
{
IFS=.
echo "$1" |read a1 b1 c1
echo "$2" |read a2 b2 c2
IFS=" "
ret=$(((a1 - a2) * 1000000 + (b1 - b2) * 1000 + c1 - c2))
test $ret -gt -1
return $?
}
vercmp 9.2.5 10.3.9
echo $?
vercmp 10.3.2 9.1.1
echo $?
vercmp 10.3.2 9.9.9
echo $?
vercmp 10.3.2 10.3.2
echo $?
returns
Tiger is definitely handling these numbers differently - when I run the code in Leopard the results are;
1
0
0
0
and in Tiger...
0
0
0
0
