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Top Forums UNIX for Beginners Questions & Answers Trying to figure out how the environment variables are being set Post 302998519 by Don Cragun on Friday 2nd of June 2017 04:28:33 PM
Old 06-02-2017
You use the dot command:
Code:
. filename

to have the current shell execute the commands in filename in your current shell execution environment. This works as long as filename is readable by you. Since the commands in filename were executed in the current shell execution environment, any variables set while it was running will be available for you to use in subsequent commands.

You use the command:
Code:
filename

(without the .) to run the commands in filename in a separate shell execution environment . When the commands in filename are done, that separate shell execution environment is deleted and anything that commands in filename did that did not change other files or were not written somewhere disappear. This doesn't work unless you have permission to execute filename and filename is on your search path for commands (as specified by the PATH environment variable).

But, it is also possible for a shell script to set up an environment and invoke an interactive database session. That script will not end until the interactive session is terminated by logging out of the database session.

All of the above are possible whether or not filename's first character is a <period>. The best way to figure out what a script might do is usually to read the file and look at the manual pages for your system to figure out what the commands in that file are doing.
 

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SCRIPT(1)						    BSD General Commands Manual 						 SCRIPT(1)

NAME
script -- make typescript of terminal session SYNOPSIS
script [-a] [-k] [-q] [-t time] [file [command ...]] DESCRIPTION
The script utility makes a typescript of everything printed on your terminal. It is useful for students who need a hardcopy record of an interactive session as proof of an assignment, as the typescript file can be printed out later with lpr(1). If the argument file is given, script saves all dialogue in file. If no file name is given, the typescript is saved in the file typescript. If the argument command ... is given, script will run the specified command with an optional argument vector instead of an interactive shell. Options: -a Append the output to file or typescript, retaining the prior contents. -k Log keys sent to program as well as output. -q Run in quiet mode, omit the start and stop status messages. -t time Specify time interval between flushing script output file. A value of 0 causes script to flush for every character I/O event. The default interval is 30 seconds. The script ends when the forked shell (or command) exits (a control-D to exit the Bourne shell (sh(1)), and exit, logout or control-d (if ignoreeof is not set) for the C-shell, csh(1)). Certain interactive commands, such as vi(1), create garbage in the typescript file. The script utility works best with commands that do not manipulate the screen. The results are meant to emulate a hardcopy terminal, not an addressable one. ENVIRONMENT
The following environment variable is utilized by script: SHELL If the variable SHELL exists, the shell forked by script will be that shell. If SHELL is not set, the Bourne shell is assumed. (Most shells set this variable automatically). SEE ALSO
csh(1) (for the history mechanism). HISTORY
The script command appeared in 3.0BSD. BUGS
The script utility places everything in the log file, including linefeeds and backspaces. This is not what the naive user expects. It is not possible to specify a command without also naming the script file because of argument parsing compatibility issues. When running in -k mode, echo cancelling is far from ideal. The slave terminal mode is checked for ECHO mode to check when to avoid manual echo logging. This does not work when in a raw mode where the program being run is doing manual echo. BSD
June 6, 1993 BSD
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