Adding a Directory to the Path

[nfo.caesar]

from: http://www.troubleshooters.com/linux/prepostpath.htm

Troubleshooters.Com and T.C Linux Library Present
Adding a Directory to the Path
Copyright (C) 2002 by Steve Litt
[ Linux Library | Troubleshooters.Com | Email Steve Litt | Copyright
Notice ]
[ See also Coasterless CD Burning ]
Contents:
  a.. Disclaimer
  b.. Pre and Post Pathing
  c.. Adding to a Single User's Path
  d.. Adding to All Users' Paths (except root)
  e.. Adding to the Path of User root
  f.. Summary
Executive Summary
Adding a directory to the path of a user or all users would seem trivial,
but in fact it isn't. The best place to add a directory to the path of a
single user is to modify that user's .bash_profile file. To add it to all
users except user root, add it to /etc/profile. To also add it to the path
of user root, add it to root's .bash_profile file.
Disclaimer
Obviously, you use this document at your own risk. I am not responsible for
any damage or injury caused by your use of this document, or caused by
errors and/or omissions in this document. If that's not acceptable to you,
you may not use this document. By using this document you are accepting this
disclaimer.

Pre and Post Pathing
Linux determines the executable search path with the $PATH environment
variable. To add directory /data/myscripts to the beginning of the $PATH
environment variable, use the following:


PATH=/data/myscripts:$PATH
To add that directory to the end of the path, use the following command:

PATH=$PATH:/data/myscripts
But the preceding are not sufficient because when you set an environment
variable inside a script, that change is effective only within the script.
There are only two ways around this limitation:

  1.. If, within the script, you export the environment variable it is
effective within any programs called by the script. Note that it is not
effective within the program that called the script.
  2.. If the program that calls the script does so by inclusion instead of
calling, any environment changes in the script are effective within the
calling program. Such inclusion can be done with the dot command or the
source command. Examples:
  . $HOME/myscript.sh
  source $HOME/myscript.sh
Inclusion basically incorporates the "called" script in the "calling"
script. It's like a #include in C. So it's effective inside the "calling"
script or program. But of course, it's not effective in any programs or
scripts called by the calling program. To make it effective all the way down
the call chain, you must follow the setting of the environment variable with
an export command.

As an example, the bash shell program incorporates the contents of file
..bash_profile by inclusion. So putting the following 2 lines in
..bash_profile:

PATH=$PATH:/data/myscriptsexport PATH
effectively puts those 2 lines of code in the bash program. So within bash
the $PATH variable includes $HOME/myscript.sh, and because of the export
statement, any programs called by bash have the altered $PATH variable. And
because any programs you run from a bash prompt are called by bash, the new
path is in force for anything you run from the bash prompt.

The bottom line is that to add a new directory to the path, you must append
or prepend the directory to the $PATH environment variable within a script
included in the shell, and you must export the $PATH environnment variable.
The only remaining question is: In which script do you place those two lines
of code?
Adding to a Single User's Path
To add a directory to the path of a single user, place the lines in that
user's .bash_profile file. Typically, .bash_profile already contains changes
to the $PATH variable and also contains an export statement, so you can
simply add the desired directory to the end or beginning of the existing
statement that changes the $PATH variable. However, if .bash_profile doesn't
contain the path changing code, simply add the following two lines to the
end of the .bash_profile file:


PATH=$PATH:/data/myscriptsexport PATH
Adding to All Users' Paths (except root)

You globally set a path in /etc/profile. That setting is global for all
users except user root. Typical /etc/profile files extensively modify the
$PATH variable, and then export that variable. What that means is you can
modify the path by appending or prepending the desired directory(s) in
existing statements modifying the path. Or, you can add your own path
modification statements anywhere before the existing export statement. In
the very unlikely event that there are no path modification or export
statements in /etc/profile, you can insert the following 2 lines of code at
the bottom of /etc/profile:


PATH=$PATH:/data/myscriptsexport PATH
Adding to the Path of User root
User root is a special case, at least on Mandrake systems. Unlike other
users, root is not affected by the path settings in /etc/profile. The reason
is simple enough. User root's path is set from scratch by its .bash_profile
script. In order to add to the path of user root, modify its .bash_profile.


Summary
A fundimental administration task is adding directories to the execution
paths of one or more users. The basic code to do so is:

PATH=$PATH:/data/myscriptsexport PATH
Place that code, or whatever part of that code isn't already incorporated,
in one of the following places:

      User Class
     Script to modify

      One user
     $HOME/.bash_profile

      All users except root
     /etc/profile

      root
     /root/.bash_profile




----------------------------------------------------------------------------
----

See also: [ Linux Library | Troubleshooters.Com | Email Steve Litt |
Copyright Notice ]

Copyright (C) 2002 by Steve Litt. -- Legal







begin 666 biglcpyr.gif
M1TE&.#EA'@`>`+,``````/__\ "__^#__P``O[\`OP"_O\# P(" @/\```#_
M`/__````__\`_P#______R'Y! $```\`+ `````>`!X```2D,,A)PQ L,S&J
M_Y8FCAWHC>AH4FFKK4'JS'1JHG1>J^>H_PY4920``C&BR<"G(SB=.I*$27M:
MH;M73-.\6J.O)3?W))>SC(NF6,6:=<B-J$LP_EIT.QAGKNO1<WU_@&-M?F][
M<AELAGV'#G$"6QET7H]!&AV!CE>)4YN<=TF?A8.0(B63BZ:GHQ-\>D(]1#]Q
6KK,N+3"YNC AO!FIOA)J1,(>$0``.P``
`
end