03-08-2011
Quote:
Originally Posted by
Perderabo
It looks to me that both red and green are closing fd 3. What book are you reading?
I do agree with you,the book named "Advanced Bash-scripting Guide"
Quote:
Originally Posted by
Corona688
It'd be more accurate to say that grep and ls get separate sets of file descriptors, so they close them individually. The shell forks twice, once to create each of those processes. FD 3 is closed in the forks but not in the original shell itself. Once they return, the exec closes FD 3 in the shell itself. That's what the exec does, changes the original shell's own file descriptors.
Thanks for your reply.What your said is the same as what i thought.We all think that FD 3 is closed in each process while the book said the process which executed the "ls" did NOT closed that.Confused...
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LEARN ABOUT DEBIAN
ppmtosixel
ppmtosixel(1) General Commands Manual ppmtosixel(1)
NAME
ppmtosixel - convert a portable pixmap into DEC sixel format
SYNOPSIS
ppmtosixel [-raw] [-margin] [ppmfile]
DESCRIPTION
Reads a portable pixmap as input. Produces sixel commands (SIX) as output. The output is formatted for color printing, e.g. for a DEC
LJ250 color inkjet printer.
If RGB values from the PPM file do not have maxval=100, the RGB values are rescaled. A printer control header and a color assignment table
begin the SIX file. Image data is written in a compressed format by default. A printer control footer ends the image file.
OPTIONS
-raw If specified, each pixel will be explicitly described in the image file. If -raw is not specified, output will default to com-
pressed format in which identical adjacent pixels are replaced by "repeat pixel" commands. A raw file is often an order of magni-
tude larger than a compressed file and prints much slower.
-margin
If -margin is not specified, the image will be start at the left margin (of the window, paper, or whatever). If -margin is speci-
fied, a 1.5 inch left margin will offset the image.
PRINTING
Generally, sixel files must reach the printer unfiltered. Use the lpr -x option or cat filename > /dev/tty0?.
BUGS
Upon rescaling, truncation of the least significant bits of RGB values may result in poor color conversion. If the original PPM maxval was
greater than 100, rescaling also reduces the image depth. While the actual RGB values from the ppm file are more or less retained, the
color palette of the LJ250 may not match the colors on your screen. This seems to be a printer limitation.
SEE ALSO
ppm(5)
AUTHOR
Copyright (C) 1991 by Rick Vinci.
26 April 1991 ppmtosixel(1)