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Some useful variables and settings in the Korn Shell

Archive - Originally posted on "The Horse's Mouth" - 2008-05-30 08:25:32 - Graham Ellis

Here are some hidden "gems" ...

• -C sets "noclobber" mode in which redirects do not overwrite files

$ set -C
$
$ ls > fred
$ ls > fred
ksh: cannot create fred: File exists
$ set +C
$ ls > fred
$

• CDPATH lets you change the target for your cd command to a list of directories whihc are searched in turn.

$ CDPATH=/etc:/bin
$ pwd
/home/trainee/sefas/f
$ cd
$ pwd
/home/trainee
$ cd init.d
/etc/init.d
$

• OLDPWD remembers where you were last in ksh, and cd - takes you there

$ pwd
/home/trainee
$ echo $OLDPWD
/etc/init.d
$ cd -
/etc/init.d
$

• Korn Shell - elapsed seconds, and a randon number between 0 and 32767

$ echo $SECONDS
14294
$ r
echo $SECONDS
14297
$ r
echo $SECONDS
14299
$ r
echo $SECONDS
14301
$ echo $RANDOM
28369
$ r
echo $RANDOM
5877
$ r
echo $RANDOM
28995
$