From: Harvey, Bruce T. (BTHarvey@LMUS.LEGGMASON.COM)
Date: Thu Nov 06 2003 - 11:53:16 EST
Incorrect. It is not an "O/S" issue. It is a "shell" issue. For example,
the lowest common denominator Bourne shell, this is true under AIX (try
running the following command using /bin/bsh rather than /bin/ksh ...
/bin/sh is a link to /bin/ksh). Korn handles all this so that variable is
in fact changed, but Bourne does not. I don't run csh or others, but why
take chances when you know there are variants that handle things
differently?
Example
----------------------------
tst.fil:
1
2
3
4
5
----------------------------
tst.shell:
variable="4"
cat tst.fil | while read f
do
variable="5"
done
echo "variable == $variable"
----------------------------
When you run tst.shell under bsh, variable == 4. Under ksh, variable == 5.
Try the others and see what you get. For csh and tcsh you probably have to
change the syntax (never used) which might invalidate the test.
Bruce T. Harvey
Legg Mason Wood Walker, Inc.
Corporate Technology - UNIX Admin.
Red Run 2nd Floor - Owings Mills, MD
(410) 580-7383 - BTHarvey@LeggMason.com
-------------------------------------------------------
-----Original Message-----
From: Zebrouvis, Lois [mailto:zebrouvis@PPG.COM]
Sent: Thursday, November 06, 2003 10:38 AM
To: aix-l@Princeton.EDU
Subject: Re: for command
that is not true for aix or hp-ux - that is a linux issue
-----Original Message-----
From: Harvey, Bruce T. [mailto:BTHarvey@LMUS.LEGGMASON.COM]
Sent: Thursday, November 06, 2003 9:36 AM
To: aix-l@Princeton.EDU
Subject: Re: for command
Keep in mind that the shell creates a subshell to feed the pipe to, such
that if you change a program variable within the 'while' loop, it will not
end up changed after the loop. For example:
variable=2
cat testfile | while read f
do
variable=3
done
when you reach here, variable is equal to 2
Just a side note to remember that I usually forget at least once every two
years or so.
Bruce T. Harvey
Legg Mason Wood Walker, Inc.
Corporate Technology - UNIX Admin.
Red Run 2nd Floor - Owings Mills, MD
(410) 580-7383 - BTHarvey@LeggMason.com
-------------------------------------------------------
-----Original Message-----
From: Paul LaMadeleine [mailto:plamadeleine@LIGHTBRIDGE.COM]
Sent: Thursday, November 06, 2003 9:22 AM
To: aix-l@Princeton.EDU
Subject: Re: for command
I usually do something like this:
cat testfile | while read line
do
echo $line
done
At 02:10 PM 11/6/2003 +0000, you wrote:
>Given the following data how do I get the following script to echo each
>line, rather than each string?
>
>for line in `cat testfile`
>do
> echo $line
>done
>
>
>testfile =
>
>hhhh jjjjjjj kkkkkkkkk
>ggggg lllllll mmmmmm
>sssss kkkkk llllll
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