Regular Expressions 101

Pro

^start of line

interface GigabitEthernet1the literal text interface GigabitEthernet1 (case sensitive)

\/the literal / (47₁₀ / 57₈ / 2F₁₆)

0the literal 0 (48₁₀ / 60₈ / 30₁₆)

\/the literal / (47₁₀ / 57₈ / 2F₁₆)

Character Class[0-9]

0-9one character from 0 (48₁₀) to 9 (57₁₀)

Positive Lookahead(?=(?:(?!\ninterface GigabitEthernet1\/0\/[0-9])[\s\S])*switchport mode access)

Non-Capturing Group(?:(?!\ninterface GigabitEthernet1\/0\/[0-9])[\s\S])*

*repeats the group contents below any number of times:

Negative Lookahead(?!\ninterface GigabitEthernet1\/0\/[0-9])

\na line-feed (newline) character (ASCII 10)

interface GigabitEthernet1the literal text interface GigabitEthernet1 (case sensitive)

\/the literal / (47₁₀ / 57₈ / 2F₁₆)

0the literal 0 (48₁₀ / 60₈ / 30₁₆)

\/the literal / (47₁₀ / 57₈ / 2F₁₆)

Character Class[0-9]

0-9one character from 0 (48₁₀) to 9 (57₁₀)

Character Class[\s\S]

\sany whitespace character

\Sany non-whitespace character

switchport mode accessthe literal text switchport mode access (case sensitive)

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

Detailed match information will be displayed here automatically.

25 tokens

Regular Expression

^interface GigabitEthernet1\/0\/[0-9](?=(?:(?!\ninterface GigabitEthernet1\/0\/[0-9])[\s\S])*switchport mode access)

New

interface GigabitEthernet1/0/1
 description abc
 bla
 switchport mode access
 xyz
 abc
interface GigabitEthernet1/0/2
interface GigabitEthernet1/0/3
 xyz
 abc
interface GigabitEthernet1/0/4
 description Test
 switchport mode access
 xyz
 abc
interface GigabitEthernet1/0/5
 description