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Full Discussion: Question regarding shells and subshells when a script is run
Top Forums Shell Programming and Scripting Question regarding shells and subshells when a script is run Post 302435161 by clx on Tuesday 6th of July 2010 01:53:18 PM
Old 07-06-2010
Quote:
Originally Posted by jim mcnamara
Alister - counterexample:

I believe this contradicts what you said about bash. What you said is true for some other shells, esp. the Bourne shell.

Code:
a=1
while read rec
do
  a=$(( $a + 1 ))
done < t.lis
echo $a

output:
Code:
3

For variables are processed inside a bash while loop, changes are visible outside the loop.
At least in this example.


I guess, there is no sub-shell involved in this or I am wrong?

Alister's statement probably meant for sub-shells.

Code:
a=1
cat t.lis | while read rec
do
  a=$(( $a + 1 ))
done 
echo $a


output: 1

Also possible, I misunderstood the scenario.
 

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LEARN ABOUT DEBIAN

surfraw-update-path

SURFRAW-UPDATE-PATH(1)					User Contributed Perl Documentation				    SURFRAW-UPDATE-PATH(1)

NAME

       surfraw-update-path - updates PATH in shell config files

SYNOPSIS

       surfraw-update-path [-add] [-remove] [-check] [-sys] [-all] [-help] [-shell=SHELL]

DESCRIPTION

       surfraw-update-path adds the surfraw elvi directory (/usr/lib/surfraw) to your PATH in your shell's config file.

       Currently it supports bash, sh, csh, tcsh, ash, dash, ksh, pdksh, zsh, rc, and es

       Don't forget to login again or source your login files for it to take effect.

OPTIONS

       -check
	   Checks to see if the surfraw config code is present.  This is the default.

       -add
	   Adds the surfraw config code.

       -remove
	   Removes the surfraw config code

       -sys
	   Updates the system-wide shell config instead of the user.  Must be done as root.

       -shell=SHELL
	   Selects the shell to configure. Defaults to the value of the $SHELL environment variable.

	   Currently supported shells are:

	   sh, ash, bash, dash, csh, tcsh, ksh, pdksh, zsh, rc, and es.

       -all
	   Attempts to configure the startup files for all known shells

       -help
	   Gives a usage message

RETURN VALUE

       -check returns 0 if the surfraw code is present in the file, 1 if it is not found, or 2 on error.

       All other options return 0 on success, or 2 on error.

ENVIRONMENT

       SHELL
	   Used to determine which shell to configure, if -shell is not given.

       HOME
	   Used to find users config files.

       ENV Used by posix-compliant shells to specify a startup rc file.

       ZDOTDIR
	   Used to find user config files for zsh. If not set, defaults to HOME.

SEE ALSO

       surfraw(1), sh(1), ash(1), bash(1), dash(1), csh(1), tcsh(1), ksh(1), pdksh(1), zsh(1), rc(1), es(1)

AUTHOR

       Ian Beckwith <ianb@erislabs.net>

perl v5.12.4							    2011-07-12						    SURFRAW-UPDATE-PATH(1)
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