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Full Discussion: Problems with "grep -vf", and exclusion files
Top Forums UNIX for Dummies Questions & Answers Problems with "grep -vf", and exclusion files Post 302877442 by frank_rizzo on Sunday 1st of December 2013 10:59:59 AM
Old 12-01-2013
Quote:
Originally Posted by Doug Lassiter
A blank "out" file is quickly created, but the command line doesn't report that it the command has finished. It just hangs. I am careful, by the way, not to have blank lines in my "exclude" file. top tells me that the grep process is still working hard (100% of CPU!), but the "out" file remains blank. That's what I call "never-never land".
The output file is not "blank" -- it's a zero length file. Any time you use the redirection operator > in a command line it will immediately truncate the file to zero regardless of file size. This happens before grep gets executes.

I am not sure why the CPU is pegged with your test case but I wanted to clarify that behaviour.
 

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LEARN ABOUT DEBIAN

g3cat

g3cat(1)						       mgetty+sendfax manual							  g3cat(1)

NAME

       g3cat - concatenate multiple g3 documents

SYNOPSIS

       g3cat [-l] [-a] g3-file1 ...

DESCRIPTION

       g3cat  concatenates  g3	files.	These can either be 'raw', that is, bitmaps packed according to the CCITT T.4 standard for one-dimensional
       bitmap encoding, or 'digifax' files, created by GNU's GhostScript package with the digifax drivers. Its output is a  concatenation  of  all
       the input files, in raw G3 format, with two white lines in between.

       If a - is given as input file, stdin is used.

       If the input data is malformed, a warning is printed to stderr, and the output file will have a blank line at this place.

OPTIONS

       -l     separate files with a one-pixel wide black line.

       -h <blank lines>
	      specifies the number of blank lines g3cat should prepend to each page. Default is 0.

       -L <lines>
	      limit lenght of output page to maximum <lines> lines.

SPECIAL-CASE OPTIONS
       -w <width>
	      specifies  the  desired  page width in pixels per line. Default is 1728 PELs, and this is mandatory if you want to send the fax to a
	      standard fax machine.  If one of the input files doesn't match this line width (for example because it was created by  a	broken	G3
	      creator), a warning is printed, and the line width is transparently fixed.

       -a     byte-align the end-of-line codes (EOL) in the file. Every EOL will end at a byte boundary, that is, with a  01 byte.

       -p <pad>
	      specifies a minimum number of bytes that each output line must be padded to.  Padding is done with 0-bits before the EOL code.

       -R     suppress output of end-of-page code (RTC).

Example
       The following example will put a header line on a given g3 page, 'page1' and put the result into 'page2':

       echo '$header' | pbmtext | pbm2g3 | g3cat - page1 >page2

FILES

       --

BUGS

       Hopefully none :-).

SEE ALSO

       g32pbm(1), sendfax(8), faxspool(1)

AUTHORS

       g3cat is Copyright (C) 1993 by Gert Doering, <gert@greenie.muc.de>

greenie 							     27 Oct 93								  g3cat(1)
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