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Full Discussion: while loops and variables under bash
Top Forums Shell Programming and Scripting while loops and variables under bash Post 302605000 by m69w on Tuesday 6th of March 2012 12:06:00 PM
Old 03-06-2012
while loops and variables under bash
Hi,

This is probably going to be very simple but i came across something i can't quite explain. Here is the situation: i have a list of files, which i'd like to process one by one (get the size, make some tests, whatever) and generate some statistics using different variables.

Something similar to this:

Code:
u=0
ls|while read f; do
#until [ $u -gt 5 ]; do
#for f in `ls `; do
echo inside u=$u
let "u+=1"
done

echo outside u=$u

And here are the results (there are 3 files in the current directory):

Quote:
inside u=0
inside u=1
inside u=2
outside u=0
So basically the variable u appears to get re-initialised somehow.

Using until or a classic for loop u keeps its value after the loop is executed, like this:

Quote:
inside u=0
inside u=1
inside u=2
inside u=3
inside u=4
inside u=5
outside u=6
So what's the deal ? That's under bash. Ksh gives similar results to the other loops.
 

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LEARN ABOUT CENTOS

devscripts.conf

DEVSCRIPTS.CONF(5)						File Formats Manual						DEVSCRIPTS.CONF(5)

NAME

       devscripts.conf - configuration file for the devscripts package

DESCRIPTION

       The  devscripts	package provides a collection of scripts which may be of use to Debian developers and others wishing to build Debian pack-
       ages.  Many of these have options which can be configured on a system-wide and per-user basis.

       Every script in the devscripts package which makes use of values from these configuration files describes the specific settings	recognised
       in its own manpage.  (For a list of the scripts, either see /usr/share/doc/devscripts/README.gz or look at the output of dpkg -L devscripts
       | grep /usr/bin.)

       The two configuration files are /etc/devscripts.conf for system-wide defaults and ~/.devscripts for per-user settings.	They  are  written
       with  bash(1)  syntax, but should only have comments and simple variable assignments in them; they are both sourced (if present) by many of
       the devscripts scripts.	Variables corresponding to simple switches should have one of the values yes and no; any other setting is regarded
       as equivalent to the default setting.

       All  variable  names  are  written  in  uppercase, and begin with the script name.  Package-wide variables begin with "DEVSCRIPTS", and are
       listed below, as well as in the relevant manpages.

       For a list of  all  of  the  available  options	variables,  along  with  their	default  settings,  see  the  example  configuration  file
       /usr/share/doc/devscripts/devscripts.conf.ex.   This  is  copied  to  /etc/devscripts.conf  when the devscripts package is first installed.
       Information about configuration options introduced in newer versions of the package will be appended to /etc/devscripts.conf when the pack-
       age is upgraded.

       Every script which reads the configuration files can be forced to ignore them by using --no-conf as the first command-line option.

PACKAGE-WIDE VARIABLES
       The currently recognised package-wide variables are:

       DEVSCRIPTS_CHECK_DIRNAME_LEVEL, DEVSCRIPTS_CHECK_DIRNAME_REGEX
	      These  variables	control  scripts  which change directory to find a debian/changelog file or suchlike, and some other miscellaneous
	      cases.  In order to prevent unwanted, even possibly dangerous, behaviour, these variables control when actions  will  be	performed.
	      The scripts which currently make use of these variables are: debc, debchange/dch, debclean, debi, debrelease, debuild and uscan, but
	      this list may change with time (and I may not remember to update this manpage).  Please see the manpages of individual  scripts  for
	      details of the specific behaviour for each script.

SEE ALSO

       devscripts(1) and /usr/share/doc/devscripts/README.gz.

AUTHOR

       This manpage was written for the devscripts package by the package maintainer Julian Gilbey <jdg@debian.org>.

DEBIAN
								 Debian Utilities						DEVSCRIPTS.CONF(5)
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