ARGF is a stream designed for use in scripts that process
files given as command-line arguments or passed in via STDIN.
The arguments passed to your script are stored in the ARGV
Array, one argument per element. ARGF assumes that any
arguments that aren't filenames have been removed from
ARGV. For example:
$ ruby argf.rb --verbose file1 file2 ARGV #=> ["--verbose", "file1", "file2"] option = ARGV.shift #=> "--verbose" ARGV #=> ["file1", "file2"]
You can now use ARGF to work with a concatenation of each of
these named files. For instance, ARGF.read will return the
contents of file1 followed by the contents of file2.
After a file in ARGV has been read ARGF removes
it from the Array. Thus, after all files have been read ARGV
will be empty.
You can manipulate ARGV yourself to control what
ARGF operates on. If you remove a file from ARGV,
it is ignored by ARGF; if you add files to ARGV,
they are treated as if they were named on the command line. For example:
ARGV.replace ["file1"] ARGF.readlines # Returns the contents of file1 as an Array ARGV #=> [] ARGV.replace ["file2", "file3"] ARGF.read # Returns the contents of file2 and file3
If ARGV is empty, ARGF acts as if it contained
STDIN, i.e. the data piped to your script. For example:
$ echo "glark" | ruby -e 'p ARGF.read' "glark\n"