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Default Environment Set by Shells...

Find out what environment a sheel defines by default...
    env - {shell} -c '/usr/bin/env'

Sh:    ---no extra environment defines---
Ksh:   PWD _

Csh:   PWD USER

Tcsh:  PWD USER SHLVL LOGNAME GROUP VENDOR REMOTEHOST
         HOST HOSTTYPE OSTYPE MACHTYPE

Zsh:   PWD HOME LOGNAME SHLVL OLDPWD _

Bash:  PWD SHELL SHLVL HOSTNAME  MACHTYPE OSTYPE OLDPWD _

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Environment handling by shells

  Bourne shell just marks variables as being exported or not exported.
Changing an exported variable also changes the value being exported.
However if you change a variable that has NOT been marked for export IN
THAT SHELL, a local copy is maintained and used and the change is not
exported (the original export variable is). The `set' command only lists
variables that have been `set' within the current shell, not the imported
environment variables. IE it will show a changed environment variable.

  Csh maintains two completely separate lists of variables for local and
environmental purposes. The local variable list overrides the environmental
when there is a clash. A few variables (like path) are linked to their
environmental counterparts (ie, PATH).

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Bourne Shell -- remove PATH component
(or MANPATH or LD_LIBRARY_PATH)

    LD_LIBRARY_PATH=`echo "$LD_LIBRARY_PATH" |
            sed 's|/opt/SUNWdxlib/[^:]*||g; s|:::*|:|g; s|^:||; s|:$||;'`
    export LD_LIBRARY_PATH
    echo "LD_LIBRARY_PATH = $LD_LIBRARY_PATH"

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