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Full Discussion: How is .profile and environment variable linked..
Top Forums Shell Programming and Scripting How is .profile and environment variable linked.. Post 91503 by blowtorch on Friday 2nd of December 2005 08:55:09 PM
Old 12-02-2005
From the man page of env:
Quote:
NAME
env - set environment for command execution

SYNOPSIS
env [-] [-i] [name = value] ... [command [arguments ...]]

DESCRIPTION
env obtains the current environment, modifies it according to its
arguments, then executes the command with the modified environment.
Arguments of the form name=value are merged into the inherited
environment before the command is executed. The -i option causes the
inherited environment to be ignored completely so that the command is
executed with exactly the environment specified by the arguments.
The simplest form of the command is to just run 'env'. This will give you the current environment, which may be used by various commands when they execute. In the more complicated form, the env command can be used to set a specified variable with the given value and that modified variable used in the environment when executing the specified command.

To understand what the above paragraph says, let us take an example (this is for ksh):
Code:
$ export ORACLE_SID=abc; export ORACLE_HOME=/oracle817
$ sqlplus internal
SQL> set pages 1000;
SQL> select name,open_mode from v$database;
NAME      OPEN_MODE
--------- ----------
ABC         MOUNTED
SQL> exit;
$ env ORACLE_SID=xyz sqlplus internal
SQL> set pages 100
SQL> select name,open_mode from v$database;
NAME      OPEN_MODE
--------- ----------
XYZ         MOUNTED
SQL> exit;
$ env|grep ORA
ORACLE_SID=abc
ORACLE_HOME=/oracle817

The above example shows how env can be used to temporarily change the environment for the duration of a single command, without actually modifying the value of the variable.

1) The 'env' command does not read from a file, the environment is stored in the memory. From the man page of environ:
Quote:
The environment of a process is accessible from C by using the global
variable:
char **environ;
2) The use of the 'list of things' that we get from the 'env' command has been explained above, to set the various environment variables, you have to use shell specific syntax.
For sh:
Code:
PATH=/usr/bin; export PATH

For ksh,bash:
Code:
export PATH=/usr/bin

For csh,tcsh:
Code:
setenv PATH /usr/bin

I think that this answers both your questions. Also, read the man pages of env and environ for more indepth explainations.
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LEARN ABOUT OPENSOLARIS

env

env(1)								   User Commands							    env(1)

NAME

       env - set environment for command invocation

SYNOPSIS

       /usr/bin/env [-i | -] [name=value]... [utility [arg... ]]

       /usr/xpg4/bin/env [-i | -] [name=value]...
	    [utility [arg... ]]

DESCRIPTION

       The  env utility obtains the current environment, modifies it according to its arguments, then invokes the utility named by the utility op-
       erand with the modified environment.

       Optional arguments are passed to utility. If no utility operand is specified, the resulting environment is written to the standard  output,
       with one name=value pair per line.

   /usr/bin
       If env executes commands with arguments, it uses the default shell /usr/bin/sh (see sh(1)).

   /usr/xpg4/bin
       If env executes commands with arguments, it uses /usr/xpg4/bin/sh (see ksh(1)).

OPTIONS

       The following options are supported:

       -i | -	     Ignores  the  environment that would otherwise be inherited from the current shell.  Restricts the environment for utility to
		     that specified by the arguments.

OPERANDS

       The following operands are supported:

       name=value     Arguments of the form name=value modify the execution environment, and are placed  into  the  inherited  environment  before
		      utility is invoked.

       utility	      The  name of the utility to be invoked.  If utility names any of the special shell built-in utilities, the results are unde-
		      fined.

       arg	      A string to pass as an argument for the invoked utility.

EXAMPLES

       Example 1 Invoking utilities with new PATH values

       The following utility:

	 example% env -i PATH=/mybin mygrep xyz myfile

       invokes the utility mygrep with a new PATH value as the only entry in its environment. In this case, PATH is used to locate  mygrep,  which
       then must reside in /mybin.

ENVIRONMENT VARIABLES

       See  environ(5)	for  descriptions of the following environment variables that affect the execution of env: LANG, LC_ALL, LC_CTYPE, LC_MES-
       SAGES, and NLSPATH.

       PATH    Determine the location of the utility. If PATH is specified as a name=value operand to env, the value given shall be  used  in  the
	       search for utility.

EXIT STATUS

       If  utility  is invoked, the exit status of env is the exit status of utility. Otherwise, the env utility returns one of the following exit
       values:

       0	 Successful completion.

       1-125	 An error occurred.

       126	 utility was found but could not be invoked.

       127	 utility could not be found.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

   /usr/bin
       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWcsu			   |
       +-----------------------------+-----------------------------+
       |CSI			     |enabled			   |
       +-----------------------------+-----------------------------+

   /usr/xpg4/bin
       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWxcu4			   |
       +-----------------------------+-----------------------------+
       |CSI			     |enabled			   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       ksh(1), sh(1), exec(2), profile(4), attributes(5), environ(5), standards(5)

SunOS 5.11							    2 Jan 2002								    env(1)
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