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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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ATF-SH(1)						    BSD General Commands Manual 						 ATF-SH(1)

NAME
atf-sh [-s shell] -- interpreter for shell-based test programs SYNOPSIS
atf-sh script DESCRIPTION
atf-sh is an interpreter that runs the test program given in script after loading the atf-sh(3) library. atf-sh is not a real interpreter though: it is just a wrapper around the system-wide shell defined by ATF_SHELL. atf-sh executes the inter- preter, loads the atf-sh(3) library and then runs the script. You must consider atf-sh to be a POSIX shell by default and thus should not use any non-standard extensions. The following options are available: -s shell Specifies the shell to use instead of the value provided by ATF_SHELL. ENVIRONMENT
ATF_LIBEXECDIR Overrides the builtin directory where atf-sh is located. Should not be overridden other than for testing purposes. ATF_PKGDATADIR Overrides the builtin directory where libatf-sh.subr is located. Should not be overridden other than for testing purposes. ATF_SHELL Path to the system shell to be used in the generated scripts. Scripts must not rely on this variable being set to select a specific interpreter. EXAMPLES
Scripts using atf-sh(3) should start with: #! /usr/bin/env atf-sh Alternatively, if you want to explicitly choose a shell interpreter, you cannot rely on env(1) to find atf-sh. Instead, you have to hardcode the path to atf-sh in the script and then use the -s option afterwards as a single parameter: #! /path/to/bin/atf-sh -s/bin/bash ENVIRONMENT
ATF_SHELL Path to the system shell to be used in the generated scripts. SEE ALSO
atf-sh(3) BSD
September 27, 2014 BSD
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