How to extract everything until first occurrence of pattern

To get L0, you may use

> library(stringr)> str_extract("L0_123_abc", "[^_]+")[1] "L0"

The [^_]+ matches 1 or more chars other than _.

Also, you may split the string with _:

x <- str_split("L0_123_abc", fixed("_"))> x[[1]][1] "L0"  "123" "abc"

This way, you will have all the substrings you need.

The same can be achieved with

> str_extract_all("L0_123_abc", "[^_]+")[[1]][1] "L0"  "123" "abc"

r regex stringr

The regex lookaround should be

str_extract("L0_123_abc", ".+?(?=_)")#[1] "L0"

r regex stringr

Using gsub...

gsub("(.+?)(\\_.*)", "\\1", "L0_123_abc")

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