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In a newer version of R,
<code>Rscript</code> or <code>Rscript.exe</code>
is a command mode of <code>R</code>
without a terminal and can be used as a shell script.
It also provides a more convenient interface than traditional ways as
```
SHELL> R --vanilla < a_rscript.r
```
or
```
SHELL> R CMD BATCH --vanilla a_rscript.r
```
or in Windows System,
```
SHELL> R.exe --vanilla < a_script.r
```
and
```
SHELL> Rcmd.exe BATCH --vanilla < a_script.r
```
or
```
SHELL> R.exe CMD BATCH --vanilla a_script.r
```
where "a_script.r" is an R script file.
<code>Rscript</code>
is also especially useful for taking in arguments from STDIN, and it is
easily utilized by other script language.
In particular, it can be a shell script as shown in the Example 1 below.
For parallel computing, "Rscript" provides an elegant way to perform
a common programming design,
<a href="./spmd.html">Single Program Multiple Data (SPMD)</a>.
More examples about batch jobs can be found at
the section
"<a href="http://www.math.ncu.edu.tw/~chenwc/R_note/index.php?item=batch">Batch jobs</a>"
and
"<a href="http://www.math.ncu.edu.tw/~chenwc/R_note/index.php?item=batch_more">Batch more</a>"
on the
<a href="http://www.math.ncu.edu.tw/~chenwc/R_note/">R_note</a>
website.
---
#### Example 1:
1. <b>Hello world !</b>
In a Unix, one can put the following in a file "an_rscript.r", then
execute as scripts in perl, php, python or any other shell scripts.
```
#!/usr/bin/Rscript --vanilla --slave
a <- c("Hello", "world", "!")
print(a)
b <- paste(a, collapse = " ")
print(b)
```
Executing the script by
```
SHELL> chmod u+x an_rscript.r
SHELL> ./an_rscript.r
```
2. <b>Batch From Command</b>
Note that the first line <code>#!/usr/bin/Rscript --vanilla --slave</code>
is not necessary for <code>Rscript</code>.
Of course, one can still use
```
SHELL> Rscript an_rscript.r
```
or
```
SHELL> Rscript -e 'source("an_rscript.r")'
```
in command mode, too.
---
#### Example 2:
1. <b>Hello world, Cottontail !</b>
Make a file called "a_cottontail.r" containing the following.
```
# File name: a_cottontail.r
a <- c("Hello", "world,", argv, "!")
print(a)
b <- paste(a, collapse = " ")
print(b)
```
Executing the script by
```
SHELL> Rscript -e 'argv <- "Cottontail"; source("a_cottontail.r")'
```
2. <b>More Cottontails !</b>
There is the other way to take in arguments from STDIN by using
<code>commandArgs()</code> in R. Let's make a file named
"cottontails.r" as the following.
```
# File name: cottontails.r
eval(parse(text = rev(commandArgs())[1]))
a <- c("Hello", "world,", argv, "!")
print(a)
b <- paste(a, collapse = " ")
print(b)
```
Executing the script by
```
SHELL> Rscript cottontails.r 'argv <- "Cottontails"'
```
---
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