writeChar
Transfer Character Strings To and From Connections

Description

Reads and writes known-length character data from and to a connection. The strings do not have to be null-terminated, but their lengths must be given.

Usage

readChar(con, nchars, useBytes = FALSE) 
writeChar(object, con, nchars = nchar(object, type = "chars"), 
    eos = "", useBytes = FALSE) 

Arguments

object a character vector containing the data to write.
con a connection object or a character string (read as a file name). If the connection is open, it should be open in binary mode and open for reading or writing, as appropriate. If it is not yet open, it is opened in binary mode; after the data is processed, it is closed.
nchars the lengths of the character strings. For readChar, this is the number of bytes in the file to read for each string. For writeChar, this is the number of bytes to write (not including the eos string). writeChar pads a string with null bytes if it is shorter than its corresponding nchars value.

eos A string to be written after each string in object. The trailing null byte is also written. Use eos=NULL to mean not to write anything after each string.
useBytes For readChar, if useBytes is TRUE, the bytes in the text strings are read as sequences of single-byte characters in the latin1 (ISO-8859-1) encoding. If FALSE (the default), these strings are interpreted as sequences of Unicode characters in the UTF-8 encoding, some of which may be encoded as multiple bytes.

For writeChar, useBytes controls the writing of both object and eos. If useBytes is TRUE, writeChar writes the bytes in the text strings as produced by charToRaw. If useBytes is FALSE (the default), the text strings are written as as sequences of Unicode characters in the UTF-8 encoding. In addition, if any element of object or eos is a string with encoding "bytes", this string is written as if useBytes was TRUE.

Value
readCharreturns the strings read.
writeCharnothing
Differences between TIBCO Enterprise Runtime for R and Open-source R
SNext S-PLUS R Diff
[cawang, 2011-06-09]: In S-PLUS, when object is a character string, nchars could be a vector or matrix.
See Also
readBin and writeBin read and write null-terminated strings. charToRaw.
Examples
con <- tempfile()
writeChar("123", con, 3)
readChar(con, 3)
 # returns "123"

writeChar( c("abc", "def"), con, c(3, 3)) readChar(con, c(4, 4)) # returns "abc" "def" # must specify nchars=c(4,4) to read terminating 0 bytes

writeChar("123", con, 5) # produces warning message: # more characters requested than are in the string - will zero-pad readChar(con, 3) # returns "123"

writeChar(c("abc","def"), con, c(3,3), eos=NULL) # write strings without ending 0 bytes readChar(con, 6) # returns "abcdef"

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