Regular Expressions 101

(?s)applies the following effective flags to the remainder of the pattern: gs

s modifier: single line. Allows a dot to match line terminators

\\the literal \ (92₁₀ / 134₈ / 5C₁₆)

newcommand{the literal text newcommand{ (case sensitive)

Group 1([^}]+)

Negated Character Class[^}]+

+matches at least one character outside the set below:

}the literal } (125₁₀ / 175₈ / 7D₁₆)

}{the literal text }{

Group 2(.+?)

.+?any Unicode character, repeated at least once

}the literal } (125₁₀ / 175₈ / 7D₁₆)

Positive Lookahead(?=\s*(?:\\newcommand|$))

\s*a Unicode whitespace character, repeated any number of times

Non-Capturing Group(?:\\newcommand|$)

1st Alternative\\newcommand

\\the literal \ (92₁₀ / 134₈ / 5C₁₆)

newcommandthe literal text newcommand (case sensitive)

2nd Alternative$

$end of string, or before its final line terminator

Global pattern flags

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

Detailed match information will be displayed here automatically.

Search reference

Regular Expression

(?s)\\newcommand{([^}]+)}{(.+?)}(?=\s*(?:\\newcommand|$))

New

\newcommand{\commandName1}{This is first command}
\newcommand{\commandName2}{This is second command with {} brackets inside
in multiple lines {} {}
}
\newcommand{\commandName3}{This is third, last command}