I have the following example file in a folder. I'd like to read files having similar name.
If I use list.files(pattern="ABC_.*?\\.csv") ,it would read all the csv file. What should I change so that it reads only ABC_001.csv and ABC_012 and similarly the other two.
ABC_001.csv
ABC_001_def.csv
ABC_012.csv
ABC_012_def.csv
Create the pattern that matches 'ABC' at the start (^) of the string followed by _, then a 0 and two digits (\\d{2}) followed by . (escape the \\. as . is a metacharacter that matches any character) and the 'csv' at the end ($) of the string
list.files(pattern = '^ABC_0\\d{2}\\.csv$', full.names = TRUE)
If it is 3 digits and not specific to 0 i.e. if we need to match 'ABC_135.csv', remove the 0 and use \\d{3} i.e. 3 digit
list.files(pattern = '^ABC_\\d{3}\\.csv$', full.names = TRUE)
It can be checked with grep
v1 <- c("ABC_001.csv", "ABC_001_def.csv", "ABC_012.csv", "ABC_012_def.csv")
grep('^ABC_0\\d{2}\\.csv$', v1, value = TRUE)
#[1] "ABC_001.csv" "ABC_012.csv"