assign the value of a command to a variable in linux

Question

I am working in R that invokes linux commands.
This is my code:

system2("wc", args = c("-l",(paste0(" ", file1),stdout = TRUE))

I need to save the word count value to a variable and call it in R. How can I do that?

WC = system2("wc", args = c("-l",(paste0(" ", file1),stdout = TRUE)) ? — G5W
– G5W, Commented Feb 16, 2017 at 20:49

Weihuang Wong · Accepted Answer · 2017-02-16 21:36:23Z

1

Your approach seems to be correct, but check your parentheses:

file1 <- tempfile()
cat("There are seven words in this sentence.", file = file1)
count <- system2("wc", args = c("-w", file1), stdout = TRUE)
as.numeric(sub(file1, "", count))
# [1] 7

answered Feb 16, 2017 at 21:36

Weihuang Wong

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5 Comments

amc794 Over a year ago

I tried this and it didn't work. It gave a 0 while the actual value is 2993. Could you suggest something?

Weihuang Wong Over a year ago

Please include a minimal working example in your question that reproduces your problem.

amc794 Over a year ago

when I run the Rscript, system2("wc", args = c("-l",(paste0(" ", file1),stdout = TRUE)) printed 2993 without a print command. But I need to call this value later in my code. So, when I tried to save this value to a variable, expected<- system2("wc", args = c("-w", file1), stdout = TRUE) and print it, it printed it as zero.

Weihuang Wong Over a year ago

Change the "-w" to "-l"?

amc794 Over a year ago

I need the line count of the file so can I still do that?

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