R Under development (unstable) (2020-12-30 r79727) -- "Unsuffered Consequences"
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> ## NB: this file must be a DOS (CRLF) format file
> 
> ## Keep comments and original formatting
> options(keep.source=TRUE)
> 
> ## simple tests that multiple lines are read correctly
> print(2+3)
[1] 5
> print(4+5)
[1] 9
> 
> ## generate some files to source
> 
> z <- c("# line 1", "2+3", "ls()", "pi", "# last line")
> 
> ## ========  LF file
> cat(z, file="testIO.R", sep="\n")
> readLines("testIO.R")
[1] "# line 1"    "2+3"         "ls()"        "pi"          "# last line"
> source("testIO.R", echo=TRUE)

> # line 1
> 2+3
[1] 5

> ls()
[1] "z"

> pi
[1] 3.141593

> # last line
> unlink("testIO.R")
> 
> ## ======== LF file, incomplete final line
> zz <- file("testIO.R", "wt")
> cat(z, file=zz, sep="\n")
> cat("5+6", file=zz)
> close(zz)
> readLines("testIO.R")
[1] "# line 1"    "2+3"         "ls()"        "pi"          "# last line"
[6] "5+6"        
Warning message:
In readLines("testIO.R") : incomplete final line found on 'testIO.R'
> source("testIO.R", echo=TRUE)

> # line 1
> 2+3
[1] 5

> ls()
[1] "z"  "zz"

> pi
[1] 3.141593

> # last line
> 5+6
[1] 11
> unlink("testIO.R")
> 
> ## ======== CRLF file
> cat(z, file="testIO.R", sep="\r\n")
> source("testIO.R", echo=TRUE)

> # line 1
> 2+3
[1] 5

> ls()
[1] "z"  "zz"

> pi
[1] 3.141593

> # last line
> readLines("testIO.R")
[1] "# line 1"    "2+3"         "ls()"        "pi"          "# last line"
> unlink("testIO.R")
> 
> ## ======== CRLF file, incomplete final line
> zz <- file("testIO.R", "wt")
> cat(z, file=zz, sep="\r\n")
> cat("5+6", file=zz)
> close(zz)
> readLines("testIO.R")
[1] "# line 1"    "2+3"         "ls()"        "pi"          "# last line"
[6] "5+6"        
Warning message:
In readLines("testIO.R") : incomplete final line found on 'testIO.R'
> source("testIO.R", echo=TRUE)

> # line 1
> 2+3
[1] 5

> ls()
[1] "z"  "zz"

> pi
[1] 3.141593

> # last line
> 5+6
[1] 11
> unlink("testIO.R")
> 
> ## ======== CR file
> cat(z, file="testIO.R", sep="\r")
> readLines("testIO.R")
[1] "# line 1"    "2+3"         "ls()"        "pi"          "# last line"
Warning message:
In readLines("testIO.R") : incomplete final line found on 'testIO.R'
> source("testIO.R", echo=TRUE)

> # line 1
> 2+3
[1] 5

> ls()
[1] "z"  "zz"

> pi
[1] 3.141593

> # last line
> unlink("testIO.R")
> 
> ## ======== CR file, incomplete final line
> zz <- file("testIO.R", "wt")
> cat(z, file=zz, sep="\r")
> cat("\r5+6", file=zz)
> close(zz)
> readLines("testIO.R")
[1] "# line 1"    "2+3"         "ls()"        "pi"          "# last line"
[6] "5+6"        
Warning message:
In readLines("testIO.R") : incomplete final line found on 'testIO.R'
> source("testIO.R", echo=TRUE)

> # line 1
> 2+3
[1] 5

> ls()
[1] "z"  "zz"

> pi
[1] 3.141593

> # last line
> 5+6
[1] 11
> unlink("testIO.R")
> 
> ## end of reg-IO.R: the next line has no EOL chars
> 2 + 2
[1] 4
>