CS 484 Week 2 topics

The boot sequence
- bootstrap loader
- LILO, the boot manager
- starting the pager
Starting system services
- runlevels
- /etc/init.d
- /etc/rc?.d
Getting on-line help
- help -- information on bash builtins
- man -- manual information
  - -k: keyword (aka appropos)
- info
  - a comprehensive documentation system
  - in emacs, use C-h i
  - can also use info
- in Debian systems look in /usr/doc
Shell programming
- Bourne shell
- Use csh as an interactive shell (if you must), but use sh (bash) for shell scripts
- quotes:
  - double quotes (") does variable expansion
  - forward quote (') string literal -- no expansion
  - back quote (`) evaluate command
- using shell history to develop small shell scripts (make sure that things work as you expect)

Example: moving (renaming) files with numeric subfields

sample file name
```
kauai-19990012-001.jpg
```

using basename, colrm, and expr

for f in kauai-19990012-???.jpg; do
	x=`basename $f .jpg`
	y=`echo $x | colrm 1 15`
	z=`expr $y + 40`
	w=`printf "%.3d" $z`
	mv $f kauai-19990012-$w.jpg
done

using sed and shell expressions

for f in kauai-19990012-???.jpg; do
	x=`echo $f | sed -e 's/kauai-19990012-0*//;s/.jpg//`
	y=$(($x + 40))
	z=`printf "kauai-19990012-%.3d.jpg" $y`
	mv $f $z
done

Unix commands
- basename, colrm, echo, expr, info, man, printf, sed

Last modified: February 15, 1999