Multiple Comparison in Bash

Checking multiple conditions in Bash can be tricky.

Following require STRING1 and STRING2 to be not empty and COUNTER < MAX.
if [[ -n "$STRING1" && -n "$STRING2" && $COUNTER -lt $MAX ]];
then
...
fi

This post is a nice concise resource.

"knitr" and "ggplot2" for Automatic LaTeX Report Generation with R

knitr is supported under R versions >2.14.1. So I upgraded R, and also needed some extra packages for ggplot2. (probably not all are required for ggplot2 but I am interested in using these packages in my research)

sudo apt-get install libX11-dev libglu1-mesa-dev libxml2-dev libgeos-dev libproj-dev libgdal-dev

Some R packages as well

install.packages(c("rgdal","maps","maptools","rgeos"))

Only, then, was I able to install knitr package according to this post.

install.packages("devtools")
library(devtools)
install_github("ggplot2","hadley")
install_github("knitr","yihui")

Package management with "apt"

Useful information can be found here.

• Search: apt-cache search [package name]
• Package info: apt-cache show [package name]

Apply Commands Only to All Files or Directories

Choose "type" to be "d" (directory) or "f" (file).
find . -type "type" -exec chmod 755 {} \; 
find . -type "type" -exec chown owner.group {} \;

More generally, any "command" will work, too.
find . -type "type" -exec "command" {} \;

Running Commands in a Sub-shell

Content is from this post

Here is how to run "/bin/script.sh" inside "/workingdir" without changing your current path.
(cd /workingdir; /bin/script.sh)

Here is how to run sequence of commands with checking status after each command by inserting "&&"
(cd /workingdir && /bin/script.sh)

Memory is better managed by using "exec" command.
(cd /workingdir && exec /bin/script.sh)