Method: IO.readlines

Defined in:
io.c

.readlines(path, sep = $/, **opts) ⇒ Array .readlines(path, limit, **opts) ⇒ Array .readlines(path, sep, limit, **opts) ⇒ Array

Returns an array of all lines read from the stream.

When called from class IO (but not subclasses of IO), this method has potential security vulnerabilities if called with untrusted input; see Command Injection.

The first argument must be a string that is the path to a file.

With only argument path given, parses lines from the file at the given path, as determined by the default line separator, and returns those lines in an array:

IO.readlines('t.txt')
# => ["First line\n", "Second line\n", "\n", "Third line\n", "Fourth line\n"]

With argument sep given, parses lines as determined by that line separator (see Line Separator):

# Ordinary separator.
IO.readlines('t.txt', 'li')
# =>["First li", "ne\nSecond li", "ne\n\nThird li", "ne\nFourth li", "ne\n"]
# Get-paragraphs separator.
IO.readlines('t.txt', '')
# => ["First line\nSecond line\n\n", "Third line\nFourth line\n"]
# Get-all separator.
IO.readlines('t.txt', nil)
# => ["First line\nSecond line\n\nThird line\nFourth line\n"]

With argument limit given, parses lines as determined by the default line separator and the given line-length limit (see Line Separator and Line Limit:

IO.readlines('t.txt', 7)
# => ["First l", "ine\n", "Second ", "line\n", "\n", "Third l", "ine\n", "Fourth ", "line\n"]

With arguments sep and limit given, combines the two behaviors (see Line Separator and Line Limit).

Optional keyword arguments opts specify:

Overloads:

  • .readlines(path, sep = $/, **opts) ⇒ Array

    Returns:

  • .readlines(path, limit, **opts) ⇒ Array

    Returns:

  • .readlines(path, sep, limit, **opts) ⇒ Array

    Returns:



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# File 'io.c', line 12155

static VALUE
rb_io_s_readlines(int argc, VALUE *argv, VALUE io)
{
    VALUE opt;
    struct foreach_arg arg;
    struct getline_arg garg;

    argc = rb_scan_args(argc, argv, "12:", NULL, NULL, NULL, &opt);
    extract_getline_args(argc-1, argv+1, &garg);
    open_key_args(io, argc, argv, opt, &arg);
    if (NIL_P(arg.io)) return Qnil;
    extract_getline_opts(opt, &garg);
    check_getline_args(&garg.rs, &garg.limit, garg.io = arg.io);
    return rb_ensure(io_s_readlines, (VALUE)&garg, rb_io_close, arg.io);
}