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Full Discussion: Insane redirection behavior
Top Forums Shell Programming and Scripting Insane redirection behavior Post 302708789 by chebarbudo on Tuesday 2nd of October 2012 08:42:56 AM
Old 10-02-2012
Insane redirection behavior
Hi guys,

I know computers don't misbehave.
But I'm puzzled by what's happening right know in a script :

I simplified the example to point out what seems weird to me.
Don't try to find any sense to this stupid script.

There are 10 rows in /tmp/tmp.txt

Code:
i=0
tmpfile=/tmp/tmp.txt
while read -r; do
    echo "$REPLY" > /dev/null
    sed "1,$((++i))d" $tmpfile | wc -l
done < $tmpfile

Code:
i=0
tmpfile=/tmp/tmp.txt
while read -r; do
    echo "$REPLY" > /dev/null
    sed "1,$((++i))d" $tmpfile > /tmp/output; wc -l /tmp/output
done < $tmpfile

In the first script, I count line from the output of sed. In the second one, I first output sed to a file and then count the lines of that file.
I see no reason why the output would be different... YET:
Code:
root@debian:~# ./script1
9
9
9
9
9
9
9
9
9
9
root@debian:~# ./script2
9 /tmp/output
8 /tmp/output
7 /tmp/output
6 /tmp/output
5 /tmp/output
4 /tmp/output
3 /tmp/output
2 /tmp/output
1 /tmp/output
0 /tmp/output

This is driving me crazy.
Do you have any sane explanation?!?

Regards
Santiago
 

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LEARN ABOUT MINIX

dh_movefiles

DH_MOVEFILES(1) 						     Debhelper							   DH_MOVEFILES(1)

NAME

       dh_movefiles - move files out of debian/tmp into subpackages

SYNOPSIS

       dh_movefiles [debhelperoptions] [--sourcedir=dir] [-Xitem] [file...]

DESCRIPTION

       dh_movefiles is a debhelper program that is responsible for moving files out of debian/tmp or some other directory and into other package
       build directories. This may be useful if your package has a Makefile that installs everything into debian/tmp, and you need to break that
       up into subpackages.

       Note: dh_install is a much better program, and you are recommended to use it instead of dh_movefiles.

FILES

       debian/package.files
	   Lists the files to be moved into a package, separated by whitespace. The filenames listed should be relative to debian/tmp/. You can
	   also list directory names, and the whole directory will be moved.

OPTIONS

       --sourcedir=dir
	   Instead of moving files out of debian/tmp (the default), this option makes it move files out of some other directory. Since the entire
	   contents of the sourcedir is moved, specifying something like --sourcedir=/ is very unsafe, so to prevent mistakes, the sourcedir must
	   be a relative filename; it cannot begin with a `/'.

       -Xitem, --exclude=item
	   Exclude files that contain item anywhere in their filename from being installed.

       file ...
	   Lists files to move. The filenames listed should be relative to debian/tmp/. You can also list directory names, and the whole directory
	   will be moved. It is an error to list files here unless you use -p, -i, or -a to tell dh_movefiles which subpackage to put them in.

NOTES

       Note that files are always moved out of debian/tmp by default (even if you have instructed debhelper to use a compatibility level higher
       than one, which does not otherwise use debian/tmp for anything at all). The idea behind this is that the package that is being built can be
       told to install into debian/tmp, and then files can be moved by dh_movefiles from that directory. Any files or directories that remain are
       ignored, and get deleted by dh_clean later.

SEE ALSO

       debhelper(7)

       This program is a part of debhelper.

AUTHOR

       Joey Hess <joeyh@debian.org>

11.1.6ubuntu2							    2018-05-10							   DH_MOVEFILES(1)
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