rsed (version 0.1.2)

streamEdit: High-level wrapper for stream editing functions

Description

High-level wrapper for stream editing functions (sed_insert, sed_replace, sed_substitute, and sed_comment) to execute any number of sequential insertion, replacement, substitution, or commenting steps.

Usage

streamEdit(commandList, stream = NULL, inFile = NULL, outFile = NULL,
  warn = FALSE)

Arguments

commandList

A list that designates the insertion, replacement, substitution, or commenting commands that will be performed on stream (or the stream obtained from inFile). The list must have names corresponding to unique abbreviations of "insert", "replace", "substitute", and/or "comment". Each element in commandList must also be a list with names and values that correspond to the arguments of sed_insert, sed_replace, sed_substitute, and/or sed_comment respectively. See Examples.

stream

A character vector, each element typically (but not necessarily) containing the text from a single line in a file, which can be generated via readLines.

inFile

A character string designating a file that is to be read (using readLines and will become a stream, where each line of the file is mapped to a single element in the character vector stream.

outFile

A character string designating a file to which the resulting, edited stream will be written using writeLines. If outFile = NULL, no file is written.

warn

A logical that, when TRUE, issues a worning if the insertion, replacement, subsitution, or commenting cannot be performed. See Details.

Value

Invisibly returns the edited stream, and writes the stream to a file if outFile is supplied.

Details

One (and only one) of inFile or stream must be specified.

If inFile and outFile are the same, a backup copy of inFile is made by appending "~" to the end of the filename, e.g., if the original file were aFile.txt, the backup would be aFile.txt~.

The value of warn in streamEdit is passed to the worker functions (sed_insert, sed_replace, sed_substitute, and sed_comment) unless the warn argument is specified for a command in commandList, in which case, for that particular command, the locally supplied value of warn takes precedence.

See Also

sed_insert, sed_replace, sed_substitute, sed_comment

Examples

# NOT RUN {
################################################################################
# Let's create an example stream we can edit
################################################################################
cat("Here's a line\n",
   "Line after which we'll insert a string\n",
   "A line we'll delete\n",
   "A line we'll replace with something else\n",
   "A line where we'll make a substitution\n",
   "A line we'll comment\n",
   "The last line\n",
   sep = "", file = "tmpTest_streamEdit.txt")

# Read the file into a 'stream'
s <- readLines("tmpTest_streamEdit.txt")

################################################################################
# Excecute a series of commands 'manually', using the individual worker functions
################################################################################

s <- sed_insert(s, after = 3, insertion = "Here's an insertion")
s <- sed_replace(s, at = "delete", replacement = NULL)
s <- sed_replace(s, at = "we'll replace", replacement = "The replacement", fixed = TRUE)
s <- sed_substitute(s, pattern = "make a substitution", replacement = "have a party")
s <- sed_comment(s, at = "comment", type = "html")
s

################################################################################
# Now execute these same commands using a single call to streamEdit(), along
# with reading the input file and writing the output file
################################################################################

# Build the list of commands
comList <- list(

 # i for 'insert', arguments for sed_insert()
 i = list(after = 3, insertion = "Here's an insertion"),

 # r for 'replace', arguments for sed_replace()
 r = list(at = "delete", replacement = NULL),

 # r for 'replace', arguments for sed_replace()
 r = list(at = "we'll replace", replacement = "The replacement", fixed = TRUE),

 # s for 'substitute', arguments for sed_substitute()
 s = list(pattern = "make a substitution", replacement = "have a party"),

 # c for 'comment', arguments for sed_comment()
 c = list(at = "comment", type = "html")

)

s1 <- streamEdit(comList, inFile = "tmpTest_streamEdit.txt",
                outFile = "tmpTest_streamEdit1.txt")
s1

# Compare the results
identical(s, s1)

# Remove the files
unlink(c("tmpTest_streamEdit.txt", "tmpTest_streamEdit1.txt"))
# }