NAME

Shell::GetEnv - extract the environment from a shell after executing commands

SYNOPSIS

use Shell::GetEnv;

$env = Shell::GetEnv->new( $shell, $command );
$status = $env->status;
$envs = $env->envs( %opts )
$env->import_envs( %opts );

DESCRIPTION

Shell::GetEnv provides a facility for obtaining changes made to environmental variables as the result of running shell scripts. It does this by causing a shell to invoke a series of user provided shell commands (some of which might source scripts) and having the shell process store its environment (using a short Perl script) into a temporary file, which is parsed by Shell::Getenv.

Communications with the shell subprocess may be done via standard IPC (via a pipe), or may be done via the Perl Expect module (necessary if proper execution of the shell script requires the shell to be attached to a "real" terminal).

The new environment may be imported into the current one, or may be returned either as a hash or as a string suitable for use with the *NIX env command.

METHODS

• new

    $env = Shell::GetEnv->new( $shell, @cmds, \%attrs );
  

  Start the shell specified by $shell, run the passed commands, and retrieve the environment. Note that only shell built-in commands can actually change the shell's environment, so typically the commands source a startup file. For example:

    $env = Shell::GetEnv->new( 'tcsh', 'source foo.csh' );
  

  The supported shells are:

    csh tcsh bash sh ksh zsh dash
  

  Attributes:

  • startup boolean

    If true, the user's shell startup files are invoked. This flag is supported for csh, tcsh, and bash. This is emulated under ksh using its -p flag, which isn't quite the same thing.

    There seems to be no clean means of turning off startup file processing under the other shells.

    This defaults to true.

  • echo boolean

    If true, put shell is put in echo mode. This is only of use when the stdout attribute is used. It defaults to false.

  • interactive boolean

    If true, put the shell in interactive mode. Some shells do not react well when put in interactive mode but not connected to terminals. Try using the expect option instead. This defaults to false.

  • login boolean

    If true, invoke the shell as a login shell. Defaults to false.

    tcsh and csh will only honor this option if no other command line options are passed. For these shells Shell::GetEnv will throw an exception if this option conflicts with another.

  • redirect boolean

    If true, redirect the output and error streams (see also the STDERR and stdout options). Defaults to true.

  • verbose boolean

    If true, put the shell in verbose mode. This is only of use when the stdout attribute is used. It defaults to false.

  • stderr filename

    Normally output from the shells' standard error stream is discarded. This may be set to a file name to which the stream should be written. See also the redirect option.

  • stdout filename

    Normally output from the shells' standard output stream is discarded. This may be set to a file name to which the stream should be written. See also the Redirect option.

  • expect boolean

    If true, the Perl Expect module is used to communicate with the subshell. This is useful if it is necessary to simulate connection with a terminal, which may be important when setting up some enviroments.

  • timeout integer

    The number of seconds to wait for a response from the shell when using Expect. It defaults to 10 seconds.

  • shellopts scalar or arrayref

    Arbitrary options to be passed to the shell.

• envs

    $env = $env->envs( [%opt] );
  

  Return the environment. Typically the environment is returned as a hashref, but if the envstr option is true it will be returned as a string suitable for use with the *NIX env command. If no options are specified, the entire environment is returned.

  The following options are recognized:

  • diffsonly boolean

    If true, the returned environment contains only those variables which are new or which have changed from the current environment. There is no way of indicating Variables which have been deleted.

  • exclude array or scalar

    This specifies variables to exclude from the returned environment. It may be either a single value or an array of values.

    A value may be a string (for an exact match of a variable name), a regular expression created with the qr operator, or a subroutine reference. The subroutine will be passed two arguments, the variable name and its value, and should return true if the variable should be excluded, false otherwise.

  • envstr boolean

    If true, a string representation of the environment is returned, suitable for use with the *NIX env command. Appropriate quoting is done so that it is correclty parsed by shells.

    If the zapdeleted option is also specified (and is true) variables which are present in the current environment but not in the new one are explicitly deleted by inserting -u variablename in the output string. Note, however, that not all versions of env recognize the -u option (e.g. those in Solaris or OS X). In those cases, to ensure the correct environment, use diffsonly = 0, zapdeleted => 0> and invoke env with the -i option.

• status

    $status = $env->status;
  

  Returns the invoked shell's status after executing the commands provided to the constructor. See "system" in perlfunc for instructions on how to interpret the status.

• import_envs

    $env->import_envs( %opt )
  

  Import the new environment into the current one. The available options are:

  • exclude array or scalar

    This specifies variables to exclude from the returned environment. It may be either a single value or an array of values.

    A value may be a string (for an exact match of a variable name), a regular expression created with the qr operator, or a subroutine reference. The subroutine will be passed two arguments, the variable name and its value, and should return true if the variable should be excluded, false otherwise.

  • zapdeleted boolean

    If true, variables which are present in the current environment but not in the new one are deleted from the current environment.

EXPORT

None by default.

SEE ALSO

There are other similar modules on CPAN. Shell::Source is simpler, Shell::EnvImporter is a little more heavyweight (requires Class::MethodMaker).

This module's unique features:

• can use Expect for the times you really need a terminal
• uses a tiny Perl program to get the environmental variables rather than parsing shell output
• allows the capturing of shell output
• more flexible means of submitting commands to the shell

DEPENDENCIES

The YAML::Tiny module is preferred for saving the environment (because of its smaller footprint); the Data::Dumper module will be used if it is not available.

The Expect module is required only if the expect option is specified.

AUTHOR

Diab Jerius, djerius@cpan.org

CONTRIBUTORS

• Marty O'Brien mob@cpan.org

COPYRIGHT AND LICENSE

Copyright 2007 Smithsonian Astrophysical Observatory

This software is released under the GNU General Public License. You may find a copy at

      http://www.gnu.org/licenses