Shell Patterns and Regular Expressions in bash
Installfest 2019

Shell Patterns *

Special Characters

• a?e ~ ace age ale ape are ate awe axe aye
• [aeiouy]h ~ ah eh oh uh
• *system ~ ecosystem subsystem system

Set of Characters

abc

List

^abc

Complement

a-c

Range

[:lower:]

Class

[=é=]

Equivalence class

[.ch.]

Collating symbol

             [[:upper:]]????*[^a-i][[=o=]]m

Absalom                Absal   -      o   m
Christendom            Christend      o   m
Chrysostom             Chrysos t      o   m
classroom              classr  o      o   m
Folsom                 Folso   -      -   m
Panmunjom              Padnmun j      o   m
Ångström               Ångst   r      ö   m

Regular Expressions .*

ERE Special Characters

• hoo?l.rs ~ preschoolers scholars scholarship
• ^[aeiouy]{3,}$ ~ aye eye yea you
• .*system ~ ecosystem subsystem system
• .+system ~ ecosystem subsystem
• ^(eco|bio).*ing ~ biopsying economizing

Extended Shell Patterns*()

layout_[0-9]*.pdf

• layout_3.pdf
• layout_31.pdf
• layout_32-test.pdf
• layout_33.pdf

• layout_3.pdf
• layout_31.pdf
• layout_32-test.pdf
• layout_33.pdf
• layout_33-final.pdf
• layout_33-final-final.pdf
• layout_33-last.pdf

Extended Pattern Matching Operators

shopt -s extglob

w=[aeiouy]   p?($w)  p@($w)  p*($w)  p+($w)  p!($w)

             p               p               p
                                             pH
             pa      pa      pa      pa
                                             pace
                             pay     pay
                             payee   payee
                             pea     pea
                             pee     pee
             pi      pi      pi      pi
                             pie     pie
                             poi     poi
                                              ...
                                              pyxes

• layout_[0-9]*.pdf
• layout_+([0-9]).pdf
• layout_+([0-9])?(-final).pdf
• layout_+([0-9])*(-final).pdf
• layout_+([0-9])@(*(-final)|?(-last)).pdf
• layout_+([0-9])*(-final|-last).pdf

Shell Patterns *
Vs

Regular Expressions .*

 layout_+([0-9])@(*(-final)|?(-last)).pdf

^layout_[0-9]+((-final)*|(-last)?)\.pdf$

Usage

Pathname Expansion (globbing)

• shopt -s globasciiranges
LC_COLLATE, LC_CTYPE, ... LC_ALL
rm [a-z]*.pdf
• shopt -s nullglob
for i in *; mkdir -p "$i"/foo; done
• shopt -s failglob
touch *
• shopt -s dotglob
rm *

• shopt -s nocaseglob
rm *.jpg
• shopt -s globstar
rm **/*.jpg
• set -f
grep [a-z][0-9]* f1
• GLOBIGNORE=*.bak:*~

Extended Test

• [ "$file" = \*.jpg ]
• [[ $file = *.jpg ]]
• [[ $file = '*.jpg' ]]

• [[ $file = a*a ]]
• [[ $file = a* && $file = *a ]]

• [[ $file = layout_+([0-9]).pdf ]]
• [[ $file =~ ^layout_[0-9]+\.pdf$ ]]
• [[ $file =~ ^layout_([0-9]+)\.pdf$ ]]
num=${BASH_REMATCH[1]}
• RE='^layout_([0-9]+)\.pdf$'
[[ $file =~ $RE ]]

for f in /var/log/**/*.log
do
   [[ $f =~ /var/log/(.*)/(.*)/(.*)/(.*).log ]] \
	|| continue
	service=${BASH_REMATCH[1]}
	Y=${BASH_REMATCH[2]}
	M=${BASH_REMATCH[3]}
	D=${BASH_REMATCH[4]}
	ln -s "$f" "/var/log/$Y$M$D-$service.log"
done
						

Case

• case $var in
     SP1|SP2) only_this;;
     SP3) test_more;;&
     SP4) do_next;&
     *) default;;
  esac

• shopt -s nocasematch

Variable Substitution

F=/var/log/access-main_12.log.gz

F=/var/log/access-main_12.log.gz

for i in !(`date +%Y-%m`*)/
do
   i=${i%/}
   p=${PWD//\//_}
   p=${p#_}
   tar cvzf "${p}_$i.tgz" "$i" \
   && rm -rf "$i"
done
						

for i in !(`date +%Y-%m`*)/
do
   i=${i%/}
   p=${PWD//\//_}
   p=${p#_}
   tar cvzf "${p}_$i.tgz" "$i" \
   && rm -rf "$i"
done
						

for i in !(2019-03*)/
do
   i=${i%/}
   p=${PWD//\//_}
   p=${p#_}
   tar cvzf "${p}_$i.tgz" "$i" \
   && rm -rf "$i"
done
						

for i in !(2019-03*)/
do
   i=${i%/}
   p=${PWD//\//_}
   p=${p#_}
   tar cvzf "${p}_$i.tgz" "$i" \
   && rm -rf "$i"
done
						

for i in 2018-12/ 2019-01/ 2019-02/
do
   i=${i%/}
   p=${PWD//\//_}
   p=${p#_}
   tar cvzf "${p}_$i.tgz" "$i" \
   && rm -rf "$i"
done
						

for i in 2018-12/ 2019-01/ 2019-02/
do
   i=${i%/}
   p=${PWD//\//_}
   p=${p#_}
   tar cvzf "${p}_$i.tgz" "$i" \
   && rm -rf "$i"
done
						

for i in 2018-12/ 2019-01/ 2019-02/
do
   i=${2018-12/%/}
   p=${PWD//\//_}
   p=${p#_}
   tar cvzf "${p}_$i.tgz" "$i" \
   && rm -rf "$i"
done
						

for i in 2018-12/ 2019-01/ 2019-02/
do
   i=2018-12
   p=${PWD//\//_}
   p=${p#_}
   tar cvzf "${p}_$i.tgz" "$i" \
   && rm -rf "$i"
done
						

for i in 2018-12/ 2019-01/ 2019-02/
do
   i=2018-12
   p=${PWD//\//_}
   p=${p#_}
   tar cvzf "${p}_$i.tgz" "$i" \
   && rm -rf "$i"
done
						

for i in 2018-12/ 2019-01/ 2019-02/
do
   i=2018-12
   p=${/var/data//\//_}
   p=${p#_}
   tar cvzf "${p}_$i.tgz" "$i" \
   && rm -rf "$i"
done
						

for i in 2018-12/ 2019-01/ 2019-02/
do
   i=2018-12
   p=_var_data
   p=${p#_}
   tar cvzf "${p}_$i.tgz" "$i" \
   && rm -rf "$i"
done
						

for i in 2018-12/ 2019-01/ 2019-02/
do
   i=2018-12
   p=_var_data
   p=${p#_}
   tar cvzf "${p}_$i.tgz" "$i" \
   && rm -rf "$i"
done
						

for i in 2018-12/ 2019-01/ 2019-02/
do
   i=2018-12
   p=_var_data
   p=${_var_data#_}
   tar cvzf "${p}_$i.tgz" "$i" \
   && rm -rf "$i"
done
						

for i in 2018-12/ 2019-01/ 2019-02/
do
   i=2018-12
   p=_var_data
   p=var_data
   tar cvzf "${p}_$i.tgz" "$i" \
   && rm -rf "$i"
done
						

for i in 2018-12/ 2019-01/ 2019-02/
do
   i=2018-12
   p=_var_data
   p=var_data
   tar cvzf "${p}_$i.tgz" "$i" \
   && rm -rf "$i"
done
						

for i in 2018-12/ 2019-01/ 2019-02/
do
   i=2018-12
   p=_var_data
   p=var_data
   tar cvzf "var_data_2018-12.tgz" "2018-12" \
   && rm -rf "2018-12"
done
						

History Control

HISTIGNORE='l[sal]:pwd: *:*\&:&'

Readline

bind -p | grep glob
"\eg": glob-complete-word
"\C-x*": glob-expand-word
"\C-xg": glob-list-expansions

cd /bin
echo b*h█ [ESC-G]
echo bash █
echo *sh█ [CTRL-X][*]
echo bash dash rbash rzsh sh zsh █
echo *sh█ [CTRL-X][G]
echo *sh█
bash   dash   rbash  rzsh   sh     zsh
						

Find

• find -name *.pdf
• find -name '*.pdf'
• find -regex '.*\.pdf$'

Shell Patterns and
Regular Expressions
in bash

Installfest 2019