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Full Discussion: Bash Variable scope - while loop while reading from a file
Top Forums UNIX for Beginners Questions & Answers Bash Variable scope - while loop while reading from a file Post 303037351 by wisecracker on Tuesday 30th of July 2019 09:51:31 AM
Old 07-30-2019
As is often the case with a little bit of jiggery pokery there is a pseudo-back-door.
The storage device can be your friend although it will slow things down with the disk thrashing and huge numbers.
NOTE: This uses 'dash' which means it is fully POSIX compliant.

Code:
#!/usr/local/bin/dash

i=0
echo "Outside loop i = ${i}."
cat self.txt | while read -r line
do
    # Read the line, there are 5 lines...
    i=$(( i + 1 ))
    echo "Line ${i}."
    echo "${i}" > i
done
i=$( cat i )
echo "Out of loop i = ${i}."

Results OSX 10.14.3, default terminal.
Code:
Last login: Tue Jul 30 14:28:01 on ttys000
AMIGA:amiga~> cd Desktop/Code/Shell
AMIGA:amiga~/Desktop/Code/Shell> chmod 755 subshell.sh
AMIGA:amiga~/Desktop/Code/Shell> ./subshell.sh
Outside loop i = 0.
Line 1.
Line 2.
Line 3.
Line 4.
Line 5.
Out of loop i = 5.
AMIGA:amiga~/Desktop/Code/Shell> _

This User Gave Thanks to wisecracker For This Post:
Adarshreddy01
 

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sh(1)							      General Commands Manual							     sh(1)

NAME

       sh - overview of various system shells

SYNOPSIS

   POSIX Shell
       option] ...  string] [arg ...]

       option] ...  string] [arg ...]

   Korn Shell
       option] ...  string] [arg ...]

       option] ...  string] [arg ...]

   C Shell
       [command_file] [argument_list ...]

   Key Shell
DESCRIPTION

   Remarks
       The POSIX .2 standard requires that, on a POSIX-compliant system, executing the command activates the POSIX shell (located in file on HP-UX
       systems), and executing the command produces an on-line manual entry that displays the syntax of the POSIX shell command-line.

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       The Bourne shell is removed from the system starting with HP-UX 11i Version 1.5.  Please use the POSIX shell as an alternative.

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	      POSIX-conforming command programming language and command interpreter
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			effect at the time the HP-UX system release was introduced, and is similar to the Korn shell in many respects.	Similar in
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	      Korn-shell command programming language and commands interpreter
			residing in file Can execute commands read from a terminal or a file.  This shell, like the POSIX shell, contains  a  his-
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	      A command language interpreter
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	      Restricted version of the POSIX shell command interpreter.
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	      restricted version of the Korn-shell command interpreter
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			shells.

	      An extension of the standard Korn Shell
			that uses hierarchical softkey menus and context-sensitive help.

							  +--------------+--------------------+
							  | To obtain:	 |  Use the command:  |
							  +--------------+--------------------+
							  | POSIX Shell  |  /usr/bin/sh ...   |
							  | Korn Shell	 |  /usr/bin/ksh ...  |
							  | C Shell	 |  /usr/bin/csh ...  |
							  | Key Shell	 |  /usr/bin/keysh    |
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       keysh(1)       Key Shell description.

       ksh(1)	      Korn Shell description.

       sh-posix(1)    POSIX Shell description.

       csh(1)	      C Shell description.

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