ENVV(1) ENVV(1)
18 April 1994
NAME
envv - manipulate environment variables in shell-independent manner
SYNOPSIS
envv [options] set env_var value
envv [options] local env_var value
envv [options] add path_var dir [pos]
envv [options] move path_var dir pos
envv [options] del path_var dir
envv [options] choose sh_val csh_val
envv [options]
OPTIONS
-e Do not escape shell meta-characters when issuing commands
-s Issue a semicolon after each command
-h Display usage information
DESCRIPTION
Envv is used to manipulate environment variables in a shell-
independent manner. It is most useful in administrator-maintained
setup files for various software packages.
Envv accepts directives, either on the command line or from standard
input, and issues shell commands tailored to the user's shell.
For example, on our system, each software package has a setup script
in a fixed directory (/usr/share/setup) which sets up environment
variables and adds directories to the users' PATH as required by the
package. The scripts to do this are slightly different for csh-like
shells (csh, tcsh) and sh-like shells (sh, ksh, bash.) Envv
eliminates the need for two separate scripts.
Envv examines the SHELL environment variable for the name of a shell
which it recognizes. If that doesn't work, it uses information from
the passwd file to find the user's shell. It then issues commands
appropriate for the shell to standard output. Here's a simple
example:
eval `envv set NAME David`
If your shell is csh, then envv emits "setenv NAME David" to standard
output. If your shell is sh, the it emits "NAME=David; export NAME"
to standard output. Either way, the environment variable is set
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18 April 1994
correctly.
SET
The simplest directive is the set command, illustrated above. Note
that shell characters are normally escaped, so that:
envv set NAME 'David* F. Skoll'
will emit "setenv NAME David\*\ F.\ Skoll" under csh. However, if the
-e option is supplied, then Envv will emit "setenv NAME David* F.
Skoll", with all the difficulties that may imply.
LOCAL
Local is similar to set, except that it does not export the variable
to the environment. Thus:
envv local name David
will emit "set name=David" in csh, and "name=David" in sh or bash.
ADD
The add directive adds the specified directory to a colon-separated
path list, if the directory is not already present. If pos is
supplied, the new directory is placed at the specified position, which
are numbered starting with 1. If pos is not specified, or is out-of-
range, the new directory is added at the end.
For example, suppose that under csh, your PATH is /bin:/usr/bin.
Then:
envv add PATH /foo yields "setenv PATH /bin:/usr/bin:/foo"
envv add PATH /foo 1 yields "setenv PATH /foo:/bin:/usr/bin"
envv add PATH /foo 2 yields "setenv PATH /bin:/foo:/usr/bin"
envv add PATH /bin yields nothing - /bin already on path
envv add PATH /bin 2 yields "setenv PATH /usr/bin:/bin"
The last example shows that an 'add' is converted to a 'move' if the
directory is already on the path, and a position is supplied. Of
course, to have any effect, all of the above examples would be used in
an eval `...` structure.
DEL
The del command deletes a directory from the path variable. Suppose
that MANPATH is set to /man:/usr/man, and that your shell is bash.
Then:
envv del MANPATH /man yields "MANPATH=/usr/man; export MANPATH"
envv del MANPATH /usr/man yields "MANPATH=/man; export MANPATH"
envv del MANPATH /foo yields nothing
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18 April 1994
MOVE
The move command moves a directory in the path to the specified
position. Suppose you're running tcsh, and the environment variable P
is set to a:b:c:d. Then:
envv move P a 2 yields "setenv P b:a:c:d"
envv move P a 999 yields "setenv P b:c:d:a"
envv move P d 1 yields "setenv P d:a:b:c"
envv move P e 1 yields nothing - e is not on path.
CHOOSE
The choose command is very simple: It takes two arguments. If the
user's shell is like sh, then the first argument is printed. If it is
like csh, then the second argument is printed.
This is useful if commercial vendors have supplied two versions of
scripts which must be sourced. Your system script can select the
proper script as follows:
source `envv choose script.sh script.csh`
This can also be used as an escape hatch for complicated tests which
really do require two separate shell scripts.
SUPPLYING DIRECTIVES ON STANDARD INPUT
If no directives are given on the command line, then envv reads
standard input for directives, which should be supplied one-per-line.
Envv processes all of the directives until end-of-file is encountered.
For example, you could do something like this:
envv << 'END_OF_STUFF' > /tmp/env.$$
set A 1
set B 2
add PATH /bin/foo
'END_OF_STUFF'
source /tmp/env.$$
rm /tmp/env.$$
This creates a temporary shell script which holds the commands to set
A and B, and add /bin/foo to the path. This temporary script is then
sourced and deleted. If you have many variables to set, this may be
faster and/or easier to maintain than multiple envv commands.
When envv reads from standard input, it uses whitespace characters to
separate directives from their arguments, and the arguments from each
other. If you want to include whitespace in an argument, escape it
with a backslash. No other characters need be escaped. For example,
if you want to set the environment variable NAME to "David Skoll", use
this in the input to envv:
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18 April 1994
set NAME David\ Skoll
NOTES
The path-manipulation directives (add, move, del) ignore trailing
slashes when comparing path components. Thus, "/usr/local" and
"/usr/local/" are considered the same. When components are added or
moved in a path variable, they inherit whatever slashes are supplied
in the dir argument. Experiment...
The path-manipulation commands can add, move or delete only one
directory at a time. For example, use this:
add PATH /foo
add PATH /bar
and not this:
add PATH /foo:/bar
AUTHOR
Envv is Copyright 1994 by David F. Skoll. It may be distributed for
free. The only fees which may be charged are normal media costs or
BBS access fees. Envv may not be distributed as part of a commercial
package. Other fees, such as support fees, consulting fees, or
special higher-than-normal BBS access fees may not be charged.
BUGS
If you have multiple add, del or move commands in a standard-input
command list, they emit multiple shell commands to set the path
variable. It would be nicer if only one command which reflected the
final result were emitted.
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