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Pattern Match

wildcard

if [[ "$fn" == *.jpg ]]

  • * to match any number of characters

  • ? to match a single character

  • [] for including a list of possible characters

shell options

shopt -s extglob
if [[ "$fn" == *.@(jpg|jpeg) ]]
extglob option deals with extended pattern matching (or globbing) and shopt -s nocasematch for case-insensitive match.

  • @(...) only one occurrence

  • +(...) one or more occurrences

  • ?(...) zero or one occurrence

  • *(...) zero or more occurrences

  • !(...) not this, but anything else

regular expression

Filename example: Ludwig Van Beethoven - 05 - "Coriolan" Overture, Op. 12.ogg

for fn in *
do
    if [[ "$fn" =~ "([[:alpha:][:blank:]]*)- ([[:digit:]]*) - (.*)$"
    then
        echo Track ${BASH_REMATCH[2]} is ${BASH_REMATCH[3]}
        mv "$fn" "Track${BASH_REMATCH[2]}"
    fi
done

  • ${BASH_REMATCH[0]} entire string matched by the regular expression

  • ${BASH_REMATCH[1]} any subexpressions, 1 ... n