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Full Discussion: echo $SHELL, $PWD and etc.
Top Forums UNIX for Dummies Questions & Answers echo $SHELL, $PWD and etc. Post 33333 by S.Vishwanath on Monday 30th of December 2002 08:01:22 AM
Old 12-30-2002
Here is the small practical example. Just check it.
Just type them on the shell & observe the output.

$a=10 (I'm creating a shell variable named as 'a' with value 10.
$set (This will show the newly created variable & its value i.e. 'a=10').
$env (This will list some set of variables other than 'a=10'.

$export a (Now Execute this statement).
$set (Now this still shows a=10 other along with some more..)
$env (Now this will show a=10 also...).

I mean, 'set' display only local & un-exported variable.
Where as 'env' shows all global & exported variable variables.

When you think of why Global & local variables, the difference
comes when using shell scripts. In a shell script if you create a
a variable, then this will be visible only for the executing script.

But, in a script if you create a variable & if you export, then it will
become a global variable, so that all scripts will be able to see this
variable.

So, using export you are making a locallly visible varialbe a Globally visible variable.

You can also do this in a single shot.

ex:- $export a=10

$ env...shows the output.

Hope this makes some sense.
 

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LEARN ABOUT CENTOS

pcp.conf

PCP.CONF(5)							File Formats Manual						       PCP.CONF(5)

NAME

       pcp.conf - the Performance Co-Pilot configuration and environment file

SYNOPSIS

       /etc/pcp.conf

DESCRIPTION

       When  using  Performance Co-Pilot (PCP) tools and utilities and when calling PCP library functions, a standard set of environment variables
       are defined in /etc/pcp.conf.  These variables are generally used to specify the location of various PCP pieces in the file system and  may
       be  loaded  into  shell scripts by sourcing the /etc/pcp.env(5) shell script and queried by C/C++ programs using the pmGetConfig(3) library
       function.  If a variable is already defined in the environment, the values in pcp.conf do not override those values,  i.e.  the	values	in
       pcp.conf serve as installation defaults only.

       Both  the  pcp.env  and	pcp.conf  files  are expected to be found in /etc by default.  If required, the pcp.conf file may be relocated and
       PCP_CONF set in the environment to specify the full path to the new location.  The pcp.env file can not be relocated (this is the only hard
       coded path required by PCP).

       The syntax rules for pcp.conf are as follows :

       1.  the general syntax is
						       PCP_VARIABLE_NAME=variable value to end of line

       2.  lines that begin with # and all blank lines are ignored.

       3.  all variables must be prefixed with PCP_.  This is a security issue - variables that do not have this prefix will be silently ignored.

       4.  there  should  be  no  space  between the variable name and the literal = and no space between the = and the variable value (unless the
	   value actually starts with a space).  This is required because the pcp.conf file may be sourced directly by Makefiles as well as inter-
	   preted by the pcp.env script and the pmGetConfig function.

       5.  variable  values  may  contain  spaces  and should not be quoted.  The pcp.env script automatically quotes all variable values from the
	   character immediately following the = through to the end of the line.

       For further details and an explanation of the use of each variable, see the comments in the /etc/pcp.conf file itself.

ENVIRONMENT

       The PCP_CONF environment variable specifies an alternative path to the pcp.conf file.

SEE ALSO

       PCPIntro(1), PCPIntro(3), PMAPI(3), pmGetConfig(3) and pcp.env(5).

Performance Co-Pilot							PCP							       PCP.CONF(5)
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