readChar {base}R Documentation

Transfer Character Strings To and From Connections


Transfer character strings to and from connections, without assuming they are null-terminated on the connection.


readChar(con, nchars)

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


con A connection object or a character string naming a file.
nchars integer, giving the lengths in characters of (unterminated) character strings to be read or written.
object A character vector to be written to the connection.
eos ‘end of string’: character string . The terminator to be written after each string, followed by an ASCII nul; use NULL for no terminator at all.


These functions complement readBin and writeBin which read and write C-style zero-terminated character strings. They are for strings of known length, and can optionally write an end-of-string mark.

If con is a character string, the functions call file to obtain an file connection which is opened for the duration of the function call.

If the connection is open it is read/written from its current position. If it is not open, it is opened for the duration of the call and then closed again. Connections can be open in either text or binary mode.

Character strings containing ASCII nul(s) will be read correctly by and appear with embedded nuls in the character vector returned.

If the character length requested for readChar is longer than the data available on the connection, what is available is returned. For writeChar if too many characters are requested the output is zero-padded, with a warning.

Missing strings are written as NA.


For readChar, a character vector of length the number of items read (which might be less than length(nchars)).
For writeChar none (strictly, invisible NULL).

See Also

The R Data Import/Export manual.

connections, readLines, writeLines, readBin


## test fixed-length strings
zz <- file("testchar", "wb")
x <- c("a", "this will be truncated", "abc")
nc <- c(3, 10, 3)
writeChar(x, zz, nc, eos=NULL)
writeChar(x, zz, eos="\r\n")

zz <- file("testchar", "rb")
readChar(zz, nc)
readChar(zz, nchar(x)+3) # need to read the terminator explicitly

[Package base version 2.2.1 Index]