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Full Discussion: Variable unexpectedly blank after piped loop
Top Forums Shell Programming and Scripting Variable unexpectedly blank after piped loop Post 303024098 by Scrutinizer on Saturday 29th of September 2018 02:15:02 PM
Old 09-29-2018
In bash and most shells the while loop the part after the pipe is executed in the background (except ksh and zsh). In those shells, once the part behind the pipe finishes, any variable content will be lost. One can avoid this like this with a code block:

Code:
echo "$var" | 
{
  while read nextline
  do
     a=blah
  done
  echo "$a"
}

Or by avoiding the pipe altogether (bash/ksh93/zsh only)
Code:
while read nextline
do
   a=blah
done <<< "$var"
echo "$a"

Last edited by Scrutinizer; 10-19-2018 at 12:54 PM.. Reason: $ sign was missing
This User Gave Thanks to Scrutinizer For This Post:
ajhlinuxuser
 

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LEARN ABOUT SUNOS

endusershell

getusershell(3C)					   Standard C Library Functions 					  getusershell(3C)

NAME

       getusershell, setusershell, endusershell - get legal user shells

SYNOPSIS

       #include <unistd.h>

       char *getusershell(void);

       void setusershell(void);

       void endusershell(void);

DESCRIPTION

       The  getusershell()  function  returns  a  pointer  to  a  legal  user  shell  as defined by the system manager in the file /etc/shells. If
       /etc/shells does not exist, the following locations of the standard system shells are used in its place:

       /bin/bash		  /bin/csh
       /bin/jsh 		  /bin/ksh
       /bin/pfcsh		  /bin/pfksh
       /bin/pfsh		  /bin/sh
       /bin/tcsh		  /bin/zsh
       /sbin/jsh		  /sbin/pfsh
       /sbin/sh 		  /usr/bin/bash
       /usr/bin/csh		  /usr/bin/jsh
       /usr/bin/ksh		  /usr/bin/pfcsh
       /usr/bin/pfksh		  /usr/bin/pfsh
       /usr/bin/sh		  /usr/bin/tcsh
       /usr/bin/zsh		  /usr/xpg4/bin/sh

       The getusershell() function opens the file /etc/shells, if it exists, and returns the next entry in the list of shells.

       The setusershell() function rewinds the file or the list.

       The endusershell() function closes the file, frees any memory used by getusershell() and setusershell(), and rewinds the file /etc/shells.

RETURN VALUES

       The getusershell() function returns a null pointer on EOF.

BUGS

       All information is contained in memory that may be freed with a call to endusershell(), so it must be copied if it is to be saved.

SunOS 5.10							    30 Aug 2004 						  getusershell(3C)
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