Regular Expressions 101

Pro

^start of line

#!the literal text #!

Group 1(/usr)?

?repeats the group contents below at most once:

/usrthe literal text /usr (case sensitive)

/bin/the literal text /bin/ (case sensitive)

Group 2(env )?

?repeats the group contents below at most once:

env the literal text env (case sensitive)

Group 3(ba)?

?repeats the group contents below at most once:

bathe literal text ba (case sensitive)

shthe literal text sh (case sensitive)

$end of line

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

Ready to run

25 tokens

^#!(/usr)?/bin/(env )?(ba)?sh$