Ross Church

This is a page on which I place notes about how to do miscellaneous things, as an aide memoire.

Making Pretty Graphs with Gnuplot

apt-get install pyxplot. Alternatively...

In gnuplot, do "set term post enh 'Times' 20"
"set nokey"
For LaTeXed labels, do "set xlabel 'xlabel'" etc.
Plot the file then run 'frob_axes.pl graph.eps newgraph.eps xlabel latex_commands...'
Open the resulting postscript in vim. Search for xlabel and move it a bit so that it's correctly aligned, ditto for ylabel.
Search for "gnulinewidth" and change the 5 to a 10.
Save the file, wondering why you didn't use a better plotting package in the first place...

Some useful gnu^WPyXPlot commands for stars output

q vs P
plot 'plot.1' u (($44-$6)/$6):45 w l
q vs R2/a
plot 'plot.2' u ($6/($44-$6)):(exp($3/.43429-(.666*log($45)+0.3333*log($44)+1.4322546))) w l

To coerce axis labels into giving you large-format equations:

'\parbox{10em}{$$\frac{\ud^2 N_{\rm coll}}{\ud M_{\star,1}\ud M_{\star,2}}$$}'

Extracting single files from a tar archive

tar xv[z]f <archive> <filename>

Making a2ps print wide text "sensibly"

a2ps -1 --landscape --font-size=10 -o postscript.ps widefile.txt
(Why is a2ps so awful?)

ftnchek

This useful program needs a little bit of massaging to make it happy:

ftnchek -columns=999 -pretty=no-long-line FILES

will stop it worrying about long lines. You may wish to add -usage=no-var-unused if you don't care about unused variables and -truncation=no-promotion to avoid lots of errors regarding promotion of variables, though you should probably fix these errors instead. -usage=no-var-uninitialized is also good if you use automatic variable initialization. Good for the Eggleton code is:

ftnchek -columns=999 -pretty=no-long-line -usage=no-var-uninitialized -usage=no-var-unused FILES

Be warned that ftnchek will tend to produce lots of output unless your code is really well written!

Chunks of files

sed 'a,b!d' filename
gets you lines a to b of the file (fanf2)
awk '(NR%10==0)' filename
gets you every tenth line of a file.

Talking to apache via telnet

GET / HTTP/1.1
User-Agent: telnet
Host: whatever

The lines need to be in the right order, it appears, or it doesn't work.

gdb

gdb is annoying, but can be useful. Note that to flush output from a fortran programme to file 'call fflush(0)' will help (thanks Ian!).

valgrind

You want valgrind --db-attach=yes .

mencoder

The following line (courtesy of Nick Law) seems to produce useful output:

mencoder mf://*.jpg -mf fps=25:type=jpg -ovc lavc -lavcopts vcodec=mpeg2video:vrc_buf_size=18350:vrc_maxrate=20000:vbitrate=15000:keyint=15 -oac copy -o output.avi

Mmmm, nice short command line there...

Meanwhile to transcode videos using avconv the following seems to work OK:

avconv -i IN.MOV -qscale 4  -b 640k -maxrate 4000k -bufsize 1835k  OUT.avi

vim

The following bits of random stuff are useful:

qa (stuff) q records macro a, @a replays it.
& replays the last substitution that you did.
:set wrap :set lbr :set showbreak=(something) will make vim wrap at line boundaries...
:%!sort pipes the current buffer through sort and replaces it with the output (this generalises in the obvious manner).
```
s/$[0-9]$$[- ]$/\1,\2/g
```
turns FORTRAN numbers without spaces between them into CSV form...

postscript

There's lots of useful postscript stuff out there; this is a very small selection as and when it comes to me

x y width height rectclip -- clip a document to a rectangle

FORTRAN arrays

If you loop over an array according to

((a(i,j),i=1,20),j=1,20)

i will change most quickly
The memory access will be faster (i.e. you should change the innermost index most quickly)

svn

To move a working copy between repositories:

svn switch --relocate $OLDURL $NEWURL

(Thanks to malc)

Sequences of numbers with bash

$ echo {1..20}
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Notes on the Eggleton Code

Computer Notes