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Top Forums Shell Programming and Scripting Question regarding shells and subshells when a script is run Post 302435120 by alister on Tuesday 6th of July 2010 11:48:42 AM
Old 07-06-2010
You are seeing that second shell because bash is spawning it to run the while loop:
Code:
tail -F $LOGFILE|while read line;do

This is also the reason why the effects of modifying variables within the while loop are not visible to the rest of the script.

Some shell implementations run the while loop within the current shell, but not bash.

Regards,
Alister
 

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OPENVT(1)							     Linux 1.x								 OPENVT(1)

NAME
openvt - start a program on a new virtual terminal (VT). SYNOPSIS
openvt [-c vtnumber] [-s] [-u] [-l] [-v] [--] command command_options DESCRIPTION
openvt will find the first available VT, and run on it the given command with the given command options, standard input, output and error are directed to that terminal. The current search path ($PATH) is used to find the requested command. If no command is specified then the environment variable $SHELL is used. OPTIONS -c vtnumber Use the given VT number and not the first available. Note you must have write access to the supplied VT for this to work. -e Directly execute the given command, without forking. This option is meant for use in /etc/inittab. -s Switch to the new VT when starting the command. The VT of the new command will be made the new current VT. -u Figure out the owner of the current VT, and run login as that user. Suitable to be called by init. Shouldn't be used with -c or -l. -l Make the command a login shell. A - is prepended to the name of the command to be executed. -v Be a bit more verbose. -w wait for command to complete. If -w and -s are used together then openvt will switch back to the controlling terminal when the com- mand completes. -- end of options to openvt. NOTE
If openvt is compiled with a POSIX (GNU) getopt() and you wish to set options to the command to be run, then you must supply the end of options -- flag before the command. EXAMPLES
openvt can be used to start a shell on the next free VT, by using the command: openvt bash To start the shell as a login shell, use: openvt -l bash To get a long listing you must supply the -- separator: openvt -- ls -l HISTORY
Earlier, openvt was called open. It was written by Jon Tombs <jon@gtex02.us.es or jon@robots.ox.ac.uk>. The -w idea is from "sam". SEE ALSO
chvt(1), doshell(8), login(1) 19 Jul 1996 V1.4 OPENVT(1)
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