Difference between ./ & . ./ ??? Post: 65295

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Top Forums Shell Programming and Scripting Difference between ./ & . ./ ??? Post 65295 by zazzybob on Friday 4th of March 2005 05:10:10 AM

03-04-2005

Registered User

When you make a script executable and invoke with ./myscript, you are specifying the path to the script (i.e. "." - the current directory). The script will then be interpreted by whatever interpreter you've sepcified in your shebang line (#!/bin/sh, for example) at the top of the script. This script will be executed in a child shell, and any variables set in the parent shell that aren't exported will not be available to the child. Also; even if you export variables in your script, they still won't exported "up" to the parent.

If you had the current directory (".") at the end of your PATH, i.e. PATH=$PATH:. you could then omit the ./ part. This is particularly bad form, and is a security risk, so I would err against this under all circumstances! It's far safer to explicity say you want to execute a script in the current directory by specifying the path (./).

When you type . ./ you are executing the commands contained within the script in the current environment, so that, for example, any variables set in the current environment that aren't exported become available to your script, and any variables set in your script become available in the current environment... observe...

Code:

$ a=1
$ cat > my_script
echo a is $a
b=2
$ . ./my_script
a is 1
$ echo $b
2

Cheers
ZB

zazzybob

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LEARN ABOUT POSIX

service

SERVICE(8)						      System Manager's Manual							SERVICE(8)

NAME

       service - run a System V init script

SYNOPSIS

       service SCRIPT COMMAND [OPTIONS]

       service --status-all

       service --help | -h | --version

DESCRIPTION

       service	runs  a System V init script or systemd unit in as predictable an environment as possible, removing most environment variables and
       with the current working directory set to /.

       The SCRIPT parameter specifies a System V init script, located in /etc/init.d/SCRIPT, or the name of a systemd unit.  The  existence  of  a
       systemd unit of the same name as a script in /etc/init.d will cause the unit to take precedence over the init.d script.	The supported val-
       ues of COMMAND depend on the invoked script. service passes COMMAND  and OPTIONS to the init script unmodified. For systemd  units,  start,
       stop, status, and reload are passed through to their systemctl/initctl equivalents.

       All scripts should support at least the start and stop commands.  As a special case, if COMMAND is --full-restart, the script is run twice,
       first with the stop command, then with the start command.

       service --status-all runs all init scripts, in alphabetical order, with the status command. The status is [ + ] for running services, [ - ]
       for stopped services and [ ? ] for services without a status command.  This option only calls status for sysvinit jobs.

EXIT CODES

       service calls the init script and returns the status returned by it.

FILES

       /etc/init.d
	      The directory containing System V init scripts.

       /{lib,run,etc}/systemd/system
	      The directories containing systemd units.

ENVIRONMENT

       LANG,  LANGUAGE,  LC_CTYPE, LC_NUMERIC, LC_TIME, LC_COLLATE, LC_MONETARY, LC_MESSAGES, LC_PAPER, LC_NAME, LC_ADDRESS, LC_TELEPHONE, LC_MEA-
       SUREMENT, LC_IDENTIFICATION, LC_ALL, TERM, PATH
	      The only environment variables passed to the init scripts.

SEE ALSO

       /etc/init.d/skeleton
       update-rc.d(8)
       init(8)
       invoke-rc.d(8)
       systemctl(1)

AUTHOR

       Miloslav Trmac <mitr@redhat.com>, Petter Reinholdtsen <pere@hungry.com>

       Licence: GNU Public Licence v2 (GPLv2)

COPYRIGHT

       2006 Red Hat, Inc.,  Petter Reinholdtsen <pere@hungry.com>

Jan 206 																SERVICE(8)

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