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Full Discussion: Array Variable being Assigned Values in Loop, But Gone when Loop Completes???
Top Forums Shell Programming and Scripting Array Variable being Assigned Values in Loop, But Gone when Loop Completes??? Post 302717889 by Corona688 on Thursday 18th of October 2012 05:08:29 PM
Old 10-18-2012
Code:
echo -n "$MY_STR" | while read ...

The main shell forks off a copy of itself to run while read independently of the echo so they can both run while connected by a pipe. The copy, or "sub-shell", runs successfully, setting all your variables and such as you please, until the pipe runs out of information and returns EOF. Then the loop quits.

Then the subshell dies. Control is returned to the main shell, which remains unchanged. You set all your variables in the subshell, not the main one.

In short: It's the pipe that does it. Your shell and everything behind the pipe are different processes and don't share variables.

Pipes are overkill if you have substring operators anyway. This way of getting a single character ought to work identically in bash and ksh:

Code:
N=0

while [ "$N" -lt "${#STRING}" ]
do
        echo "${STRING:$N:1}"
        let N=N+1
done

This User Gave Thanks to Corona688 For This Post:
mrm5102
 

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LEARN ABOUT HPUX

echo

echo(1) 						      General Commands Manual							   echo(1)

NAME

       echo - echo (print) arguments

SYNOPSIS

       [arg] ...

DESCRIPTION

       writes  its  arguments  separated by blanks and terminated by a new-line on the standard output.  It also understands C-like escape conven-
       tions; beware of conflicts with the shell's use of

	      write an alert character
	      backspace
	      print line without appending a new-line
	      form-feed
	      new-line
	      carriage return
	      tab
	      vertical tab
	      backslash
	      the 8-bit character whose
			ASCII code is the 1-, 2-, 3- or 4-digit octal number n, whose first character must be a zero.
	      write an 8-bit value that is the zero-, one-, two- or three-digit octal number
			num

       is useful for producing diagnostics in command files and for sending known data into a pipe.

   Notes
       Berkeley differs from this implementation.  The former does not implement the backslash escapes.  However, the semantics of the escape  can
       be obtained by using the option.  The echo command implemented as a built-in function of follows the Berkeley semantics (see csh(1)).

EXTERNAL INFLUENCES

   Environment Variables
       determines the interpretation of arg as single and/or multi-byte characters.

       If is not specified in the environment or is set to the empty string, the value of is used as a default for each unspecified or empty vari-
       able.  If is not specified or is set to the empty string, a default of "C" (see lang(5)) is used instead  of  If  any  internationalization
       variable contains an invalid setting, behaves as if all internationalization variables are set to "C".  See environ(5).

   International Code Set Support
       Single- and multi-byte character code sets are supported.

AUTHOR

       was developed by OSF and HP.

SEE ALSO

       sh(1).

BUGS

       No characters are printed after the first This is not normally a problem.

STANDARDS CONFORMANCE

																	   echo(1)
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