Parsing out a line in R to pick different objects - regex

Question

I have this line:
system<-c("System configuration: type=Shared mode=Uncapped smt=4 lcpu=96 mem=393216MB psize=64 ent=16.00")
I need to parse out this and pick smt, lcpu, mem, mpsize and ent into different objects.
For example, I doing this to pick the smt, but it picks the whole line, any ideas what I am doing wrong here?
smt<-sub('^.* smt=([[:digit:]])', '\\1', system)
smt needs to have a number 4 in this case.

Answer 1

I would use strsplit a couple times, and type.convert:
parse.config <- function(x) {
clean <- sub("System configuration: ", "", x)
pairs <- strsplit(clean, " ")[[1]]
items <- strsplit(pairs, "=")
keys <- sapply(items, `[`, 1)
values <- sapply(items, `[`, 2)
values <- lapply(values, type.convert, as.is = TRUE)
setNames(values, keys)
}
config <- parse.config(system)
# $type
# [1] "Shared"
#
# $mode
# [1] "Uncapped"
#
# $smt
# [1] 4
#
# $lcpu
# [1] 96
#
# $mem
# [1] "393216MB"
#
# $psize
# [1] 64
#
# $ent
# [1] 16
The output is a list so you can access any of the parsed items, for example:
config$smt
# [1] 4

Answer 2

Using strapplyc in the gusbfn package the following creates a list L whose names are the left hand sides such as smt and whose values are the right hand sides.
library(gsubfn)
LHS <- strapplyc( system, "(\\w+)=" )[[1]]
RHS <- strapplyc( system, "=(\\w+)" )[[1]]
L <- setNames( as.list(RHS), LHS )
For example we can now get smt like this (and similarly for the other left hand sides):
> L$smt
[1] "4"
UPDATE: Simplified.

Answer 3

add .* to the end of your matching expression and you'll get "4".
sub('^.* smt=([[:digit:]]+).*', '\\1', system)
You may want to add the + I included in the instance where it is more than a single digit.
You could also approach this by splitting on spaces and the finding the matches:
splits <- unlist(strsplit(system, ' '))
sub('smt=', '', grep('smt=', splits, value=TRUE))
# [1] "4"
or wrapping it in a function:
matchfun <- function(string, to_match, splitter=' ') {
splits <- unlist(strsplit(string, splitter))
sub(to_match, '', grep(to_match, splits, value=TRUE))
}
matchfun(system, 'smt=')
# [1] "4"

Answer 4

Well, I'm voting for #GaborGrothendieck's, but am offering this as a more pedestrian alternative:
inp <- c("System configuration: type=Shared mode=Uncapped smt=4 lcpu=96 mem=393216MB psize=64 ent=16.00")
inparsed <- read.table(text=inp, stringsAsFactors=FALSE)
vals <- unlist(inparsed)[grep("\\=", unlist(inparsed))]
vals
# V3 V4 V5 V6 V7 V8 V9
# type=Shared mode=Uncapped smt=4 lcpu=96 mem=393216MB psize=64 ent=16.00
vals[grep("smt|lcpu|mem|mpsize|ent", vals)]
V5 V6 V7 V9
"smt=4" "lcpu=96" "mem=393216MB" "ent=16.00"
I would note that choosing the name 'system' for a variable seems most unwise in light of the system function's existence.