readLines {base}R Documentation

Read Text Lines from a Connection

Description

Read text lines from a connection.

Usage

readLines(con = stdin(), n = -1, ok = TRUE)

Arguments

con A connection object or a character string.
n integer. The (maximal) number of lines to read. Negative values indicate that one should read up to the end of the connection.
ok logical. Is it OK to reach the end of the connection before n > 0 lines are read? If not, an error will be generated.

Details

If the 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 from its current position. If it is not open, it is opened for the duration of the call and then closed again.

If the final line is incomplete (no final EOL marker) the behaviour depends on whether the connection is blocking or not. For a blocking text-mode connection (or a non-text-mode connection) the line will be accepted, with a warning. For a non-blocking text-mode connection the incomplete line is pushed back, silently.

Whatever mode the connection is opened in, any of LF, CRLF or CR will be accepted as the EOL marker for a line.

Value

A character vector of length the number of lines read.

See Also

connections, writeLines, readBin, scan

Examples

cat("TITLE extra line", "2 3 5 7", "", "11 13 17", file="ex.data",
    sep="\n")
readLines("ex.data", n=-1)
unlink("ex.data") # tidy up

## difference in blocking
cat("123\nabc", file = "test1")
readLines("test1") # line with a warning

con <- file("test1", "r", blocking = FALSE)
readLines(con) # empty
cat(" def\n", file = "test1", append = TRUE)
readLines(con) # gets both
close(con)

unlink("test1") # tidy up

[Package base version 2.1.0 Index]