readLines {base}

R Documentation

Read Text Lines from a Connection

Description

Read some or all text lines from a connection.

Usage

readLines(con = stdin(), n = -1L, ok = TRUE, warn = TRUE,
          encoding = "unknown")

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 input on 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.
warn	logical. Warn if a text file is missing a final EOL.
encoding	encoding to be assumed for input strings. It is used to mark character strings as known to be in Latin-1 or UTF-8: it is not used to re-encode the input. To do the latter, specify the encoding as part of the connection con or via options(encoding=): see the example under file.

Details

If the con is a character string, the function calls file to obtain a 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 in "rt" mode 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 non-blocking text-mode connection the incomplete line is pushed back, silently. For all other connections the line will be accepted, with a warning.

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.

The elements of the result have a declared encoding if encoding is "latin1" or "UTF-8",

Note

The default connection, stdin, may be different from con = "stdin": see file.

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

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