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Vlookup Snippet in Command Line

Aug 6, 2018 #shell

A general Rscript to run in command line, to extract value from table.

#!/usr/bin/env Rscript --vanilla

# read from stdin
p <- arg_parser(description = "Parse value from a table read from a text file.")

# required arguments
p <- add_argument(p, c("txt", "--key", "--value", "--lookup"), 
                  help = c("text file", "key identifier", "key id value", "item to lookup"))
p <- add_argument(p, "--regex", help = "regex pattern to extract, if any", default = ".*")
args <- parse_args(p)

# mimic vlookup function in Excel
vlookup <- function(this, df, key, lookup) {
    m <- match(this, df[[key]])

# read from text file 
df <- read_table(args$txt)

# extract value
val <- with(args, vlookup(value, df, key, lookup))

# extract pattern (optional)
str_extract(val, args$regex)

For example: docker-machine ls gives

NAME    ACTIVE   DRIVER       STATE     URL                         SWARM   DOCKER        ERRORS
myvm1   -        virtualbox   Running   tcp://           v18.05.0-ce
myvm2   -        virtualbox   Running   tcp://           v18.05.0-ce

To extract IP address of a particular virtual machine, we can do

docker-machine ls > machines.txt

vlookup.R -k NAME -v myvm1 -l URL -r "\\d{3}(\\.\\d{2,3})+" machines.txt
Parsed with column specification:
  NAME = col_character(),
  ACTIVE = col_character(),
  DRIVER = col_character(),
  STATE = col_character(),
  URL = col_character(),
  SWARM = col_character(),
  DOCKER = col_character(),
  ERRORS = col_character()
[1] ""