Extract substring between two colons / special characters

Question

I want to extract "SUBSTRING" with sub() from the following string:

attribute <- "S4Q7b1_t1_r1: SUBSTRING: some explanation: some explanation - ..."

I used the following code, but unfortunately it didn't work:

sub(".*: (.*) : .*", "\\1", attribute) 

Does anyone know an answer for that?

Answer 1

You may use

sub("^[^:]*: ([^:]*).*", "\\1", attribute) 

See the regex demo

You need to rely on negated character classes, [^:] that matches any char but : , since .* matches greedily any 0 or more chars. Also, your pattern contains a space before : and it is missing in the string.

Details

• ^ - start of string
• [^:]* - any 0+ chars other than :
• : - a colon with a space - ([^:]*) - Capturing group 1 ( \\1 refers to this value): any 0+ chars other than :
• .* - the rest of the string.

R Demo :

attribute <- "S4Q7b1_t1_r1: SUBSTRING: some explanation: some explanation - ..."
sub("^[^:]*: ([^:]*).*", "\\1", attribute) 
## => [1] "SUBSTRING"