Useful bash, and linux commands

A short list of some useful commands that crossed my path

PDF related

To extract some pages from a pdf file:

gs -sDEVICE=pdfwrite -dNOPAUSE -dBATCH -dFirstPage=1 -dLastPage=10 -sOutputFile=output.pdf input.pdf

CSV in bash

# Here skipping the first line using sed, then piping to the while loop
sed 1d $file | while read col1 col2 col3
do
   echo $col1 $col2 $col3
done

Tests on string in bash

if [ -z "$var" ];

Or

[ -z "$var" ] && echo "Empty"

Determine if var is empty:

[[ ! -z "$var" ]] && echo "Not empty" || echo "Empty"

if [ -z "$var" ]
then
      echo "\$var is empty"
else
      echo "\$var is NOT empty"
fi