R: Code Execution

Theory

R is a language and environment for statistical computing and graphics. It is a GNU project which is similar to the S language and environment which was developed at Bell Laboratories (formerly AT&T, now Lucent Technologies) by John Chambers and colleagues.

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Practical

System Commands

# System()
system("ls -l") # Executes the ls -l command in Unix-like systems

# System2()
output <- system2("ls", args = "-l", stdout = TRUE)
output

# Shell()
shell("ls -l")

File Reading

# read.csv()
data <- read.csv("file.csv")

# read.table()
data <- read.table("file.txt", sep = "\t", header = TRUE)

# readLines()
lines <- readLines("/etc/passwd")

# scan()
data <- scan("file.txt", what = "character", sep = ",")

# file()
con <- file("file.txt", "r")

List Directory Contents

# dir()
files <- dir()
print(files)

# file.access()
file.access(dir("/etc/"))

• 0: No access permissions.

• 1: Execute access.

• 2: Write access.

• 4: Read access.

• 6: Read and write access.

• 7: Read, write, and execute access.

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REFERENCES

• https://cran.r-project.org/web/packages/sys/sys.pdf

• https://www.rdocumentation.org/packages/base/versions/3.6.2/topics/system

• https://www.r-bloggers.com/2021/09/how-to-use-system-commands-in-your-r-script-or-package/

• https://stat.ethz.ch/R-manual/R-devel/library/base/html/system.html