What is export ORACLE_SID
export, set and setenv commands
are used in UNIX for setting value of a variable or an environment variable. In
order to understand the difference between the set, setenv and export UNIX commands,
the user should know the difference between a normal variable and
an environment variable.
Let us consider an
example. In k-shell or bourne shell, a variable is defined as shown below:
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# FILE=”output.txt”
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This means the variable FILE is assigned
a value 'output.txt'. This value can be checked by doing "echo
$FILE". This FILE variable is a normal or local variable. This
assignment makes the scope of this variable only inside the shell in
which it is defined. Any shell or a process invoked from the original
shell will not have the variable FILE defined as shown below.
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#FILE=”output.txt”
#echo $FILE
output.txt
#ksh
#echo $FILE
#
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There are instances or situations where
we would like to define a variable and it should be accessed in all the shells
or processes invoked by the original shell. This can be achieved by the export command
in ksh/sh as shown below.
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#export FILE=”output.txt”
#echo $FILE
output.txt
#ksh
#echo $FILE
output.txt
#
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This FILE variable is now an
environment variable. An environment variable is the one which can be accessed
across all the shells or processes initiated from the original shell of the
environment. So, in ksh/sh, a variable can be made an environment variable
using the export command.
set and setenv are
the c-shell/tc-shell alternatives for setting a local variable and environment
variable respectively. The set command is used for setting local variable,
setenv is uesd for setting an environment variable:
The example below shows the set command
usage:
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#set FILE=”output.txt”
#echo $FILE
output.txt
#tcsh
#echo $FILE
#
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The example below shows the setenv command
usage:
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#setenv FILE ”output.txt”
#echo $FILE
output.txt
#tcsh
#echo $FILE
output.txt
#
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