Just a few notes on writing shell scripts in general:
Filenames:
bash, ksh, and recent SysV[34] shells all include $RANDOM, so a name
like /tmp/$$_$RANDOM gives unique filenames. For the deeply paranoid who
might have old files around, you can:
MyFile=/tmp/$$_$RANDOM.myapp
while [ -f $MyFile ]; do MyFile=/tmp/$$_$RANDOM.myapp; done
while will give you a unique name. Of course it indicates other
problems with old files hanging around, but that's not the issue.
Results of command execution:
Accent grave is more portable than paren notation, so `cmd` works in
more places than $(cmd). On the other hand, $(is easier to read) if you
know you will have a recent shell.
Arithmetic:
most portable is the use of expr to do math. If you accept that the
"let" capability has been around for a decade, as has $((...)) notation,
you can cut a few corners. If don't know if SysV shell has the $[...]
notation supported by bash/ksh, but if total portability is my goal I
still use expr.
In order or partability:
a=`expr $a + 4`
a=$(($a+4))
let a=a+4
a=$[a+4]
Functions and alias:
Yes, there are still shells around which lack them. Not anything
modern, but SysV2 shell is not as dead as it deserves to be :-(
None of this is a comment on existing code, just a few tricks I picked
up when doing support for scripts which had to run on everything from
SysIII to BSD, including Xenix. Hopefully they will save someone some
time.
--
-bill davidsen ([EMAIL PROTECTED])
"The secret to procrastination is to put things off until the
last possible moment - but no longer" -me
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