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Top Forums Shell Programming and Scripting [BASH] Problem with a sed -n statement Post 302599836 by EdinburghLad on Saturday 18th of February 2012 09:38:57 PM
Old 02-18-2012
[BASH] Problem with a sed -n statement

Hey all,

So I've been banging my head against this for a few hours (Smilie) and I can't see whats wrong with it, each part seems to work fine on its own when entered at command line, but then it falls down when pulled together.

I'm writing a script to translate fractional atomic coordinates to cartesian coordinates, itself a simple mathematical thing, but the input format is giving me trouble. The code should read in a .xyz file, which has 2 comment lines and then so many lines of atom x y z like so

48
Optimisation video
H 1.0000 1.0000 1.0000
C 1.2000 1.3000 1.3333
.
.
.
48
Optimisation Video
H 1.2000 1.2000 1.2000
C 2.0000 2.0000 2.0000
.
.
.


before being repeated (two comment lines etc) in a number of frames ($NoFrames), building up an animation of how the atoms move.

Ultimately I need to pull out each atom line and disregard the comment lines. I thought what I'd written (below) should do that but for some reason my sed -n statement always pulls out the comment lines as well

Code:
# $NoFrames and $NoAtoms are defined earlier in the code and do not change
#
# Start of the systematic loop, outer deals with frames, inner with atoms
#
FrameNumber=0 # Used to know which line the sed statement should strip out
FrameCounter=1 # Keeps a track of which frame we're analysing
AtomCounter=1 # Keeps a track of which atom (within each frame) we're analysing
while [[ $FrameCounter -le $NoFrames ]]; do
        while [[ $AtomCounter -le $NoAtoms ]]; do
                let "AdjustedAtomCounter=(($FrameNumber*($NoAtoms+2))+($AtomCounter+2))" # This line should allow me to skip the first two lines per frame (the comment lines)
                sed -n "${AdjustedAtomCounter}p" *.xyz
                let "AtomCounter=$AtomCounter+1"
        done
echo $NoAtoms >> Cartesian.xyz
echo "Cartesian GeomOpt Video" >> Cartesian.xyz
let FrameCounter=FrameCounter+1
let FrameNumber=FrameNumber+1
let AtomCounter=1
done
rm *.txt
exit

I've stripped all the code back to this, If i can get this part to work i can send the values off to be processed and then written into the output (Cartesian.xyz) file. Any help with this would be greatly appreciated and I hope I've made the problem as clear as I can, but please do tell me if I need to elaborate on something.

Cheers!
 

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LPBB(4) 						   BSD Kernel Interfaces Manual 						   LPBB(4)

NAME
lpbb -- parallel port I2C bit-banging interface SYNOPSIS
device iicbus device iicbb device lpbb device iic DESCRIPTION
The lpbb driver supports the Philips official I2C parallel bit-banging interface. LS05 pin 14 (Vcc) o ------- | | | +--+--+---------------------+--+--+------------+------+-o 1 | | | | | | | ===.1uF | +5V | -------- [R][R][R] 3x10K 3x10K [R][R][R] LS05 | | | | | | | | | | | pin 7 o-+------+-o 2 | | 12 o-+--+ | | 3| 4 | | | (Gnd) | GND | | 17 o-+-----|--|----| >o-------------+--|--|--------------+ | | | | | | |/ 8 /|9 | | 10 /|11 +----+-o 3 | | 15 o-+-----+--|--------------o< |------+--|------o< |----+ | SCL | | | | 1| 2 | | | | | | 9 o-+--------|----| >o-------------------+--------------+----+-o 4 | | | | |/ 6 /|5 | | SDA | | 11 o-+--------+----------------------------------o< |----+ ------- | 10 o-+-+ | 4-pin | 13 o-+-+--oGND Connector | 25 o-+-+ ------------------ Part List -------------------------- -------- | 1 - .1 uF capacitor | 6 - 10K 5% resistors | 25-pin male D | 1 - 4-pin connector | 1 - 25-pin male D connector | connector to PC | 1 - 74LS05 open collector hex inverter | printer port ------------------------------------------------------- SEE ALSO
iicbb(4), iicbus(4), ppbus(4) HISTORY
The lpbb manual page first appeared in FreeBSD 3.0. AUTHORS
This manual page was written by Nicolas Souchu. BSD
October 25, 1998 BSD
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