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rregexstringstringi

Remove everything before a certain occurrence identified by position in string

I have a string looking like a.

I would like to delete everything before the 2nd to last occurrence of the patter === test, === included.

a <- "=== test : {abc}
      === test : {abc}
      === test : {abc}
      === test : {aUs*} 
      === dce
      === test : {12abc}
      === abc
      === test : {abc}
      === test : {dfg}"

result <- "test : {abc}
           === test : {dfg}"

I tried: 

gsub(".*=== test", "", a)

How to set the index 2nd to last?

Thanks

Solution

  • We can use strsplit to split by line breaks and pick the last two elements. paste them together and use sub to remove the === in the beginning:

    sub("^=== ", "", paste(tail(strsplit(a, split = "\\n")[[1]], 2), collapse = "\n"))
# [1] "test : {abc}\n=== test : {dfg}"