Cheat sheet

• script to execute a command in all subdirectories
  • YOUR_TOP_LEVEL_FOLDER=$PWD
  • for dir in `ls $YOUR_TOP_LEVEL_FOLDER`;
  • do
  • cd $YOUR_TOP_LEVEL_FOLDER/$dir
  • echo $PWD
  • # Command
  • done
• To mount directory from a remote machine
  • sshfs user@machine:absolute_path target_directory
• To unmount it
  • fusermount -u directory
• To see a running process
  • ps -ef |grep Process_name
• Kill all processes
  • kill -9 -1
• To synchronize
  • rsync -avz --exclude='files' source destination
• Finding files and processing
  • find DIR -name 'file_name' -exec COMMAND {} \;
• Finding difference between two folders
  • diff -rq folderA folderB
• sed examples
  • Find and replace strings in a file using sed
    • sed -i 's/text_old/text_new/g'
  • Replacing text on specific line(s)
    • sed -i '32c 5.0'
  • printing a particular line
    • sed -n '32p' file
  • Deleting lines
    • sed -i '1,3d' file
• To avoid segmentation faults when running code with large arrays
  • ulimit -s unlimited: sets the stack size to unlimited
• To dump the svn repository
  • svnadmin dump /home/syed/svn > dump_file
• To add new file to a svn repository
  • svn add file_name (after adding, a svn commit has to be done)
• Customizing shell prompt
  • Shell prompt (e.g. [syed@mm24 src]$ ) is stored in the environmental variable PS1. Set it as you wish, e.g. PS1='[\u@\h \w]\$'
    • See http://www.cyberciti.biz/tips/howto-linux-unix-bash-shell-setup-prompt.html
• Running a command with reduced priority(19(-19) lowest(highest))
  • nice -n 19 command-name
• To see hostname of a machine using ip-address use 'nslookup'
• To compress huge avi files
  • mencoder old_file.avi -o new_file.avi -oac copy -ovc lavc -lavcopts vcodec=mpeg4:mbd=1:vbitrate=3800
  • mencoder old_file.avi -o new_file.wmv -ovc copy -ovc lavc -lavcopts vcodec=wmv2:mbd=1:vbitrate=2800
  • see http://wiki.quakeworld.nu/Mencoder_howto
• Embedding fonts in pdf file
  • dvips -t a4 paper.dvi
  • ps2pdf -dPDFSETTINGS=/prepress -dEmbedAllFonts=true paper.ps
• Merging pdf files (http://www.linux.com/archive/feed/36815)
• gs -dBATCH -dNOPAUSE -q -sDEVICE=pdfwrite -sOutputFile=finished.pdf file1.pdf file2.pdf
• extract frames from a movie
  • ffmpeg -i inputfile.avi -r 1 -f image2 image-%3d.jpeg
• Delete all files inside remote directory using ssh
  • ssh HOSTNAME rm -rf "/path/to/the/directory/*"
• how to combine two seperate videos into one left-right video
  • http://wiki.multimedia.cx/index.php?title=How_to_make_a_3d_movie_with_ffmpeg#references
• How to download all files from a website using wget
  • wget -A pdf,jpg -m -p -E -k -K -np http://site/path/
• Convert avi to gif
  • mkdir frames
  • ffmpeg -i Video\ 3.wmv frames/ffout%03d.png
  • Delete if too many frames: find . -maxdepth 1 -not -iname "*1.png" -exec rm {} \;
  • convert -delay 10 -loop 10 frames/ffout*.png output.gif

Gnuplot

• "Fractions" in gnuplot for y axis labels: Put characters on top of each other using '~' and draw a line.
  • set ylabel '{/Symbol ~{s}{1.2s}}_{~Y{1.5xy}}' rotate by -0 font 'Times-Italic'
    • set arrow nohead from -6.27, 0. to -5.79,0.
  • set ylabel "{/*1.2 { /Symbol,45 s_{qq}}}\n{\261\261\261\n}{/*1.2{/Symbol,1 s^\245}}" rotate by 0 offset 2
• Gnuplot use of "every I:J:K:L:M:N" (from: http://t16web.lanl.gov/Kawano/gnuplot/datafile2-e.html