Rebuilds the hash based on the current hash values for each key. If values of key objects have changed since they were inserted, this method will reindex hsh. If Hash#rehash is called while an iterator is traversing the hash, a RuntimeError will be raised in the iterator.
a = [ "a", "b" ] c = [ "c", "d" ] h = { a => 100, c => 300 } h[a] #=> 100 a[0] = "z" h[a] #=> nil h.rehash #=> {["z", "b"]=>100, ["c", "d"]=>300} h[a] #=> 100
Returns a new hash consisting of entries for which the block returns false.
If no block is given, an enumerator is returned instead.
h = { "a" => 100, "b" => 200, "c" => 300 } h.reject {|k,v| k < "b"} #=> {"b" => 200, "c" => 300} h.reject {|k,v| v > 100} #=> {"a" => 100}
Equivalent to Hash#delete_if, but returns nil if no changes were made.
Returns a new hash created by using hsh’s values as keys, and the keys as values. If a key with the same value already exists in the hsh, then the last one defined will be used, the earlier value(s) will be discarded.
h = { "n" => 100, "m" => 100, "y" => 300, "d" => 200, "a" => 0 } h.invert #=> {0=>"a", 100=>"m", 200=>"d", 300=>"y"}
If there is no key with the same value, Hash#invert is involutive.
h = { a: 1, b: 3, c: 4 } h.invert.invert == h #=> true
The condition, no key with the same value, can be tested by comparing the size of inverted hash.
# no key with the same value h = { a: 1, b: 3, c: 4 } h.size == h.invert.size #=> true # two (or more) keys has the same value h = { a: 1, b: 3, c: 1 } h.size == h.invert.size #=> false
Replaces the contents of hsh with the contents of other_hash.
h = { "a" => 100, "b" => 200 } h.replace({ "c" => 300, "d" => 400 }) #=> {"c"=>300, "d"=>400}
Returns true if the given key is present in hsh.
h = { "a" => 100, "b" => 200 } h.has_key?("a") #=> true h.has_key?("z") #=> false
Note that include? and member? do not test member equality using == as do other Enumerables.
See also Enumerable#include?
Same as ENV#delete_if, but works on (and returns) a copy of the environment.
Equivalent to ENV#delete_if but returns nil if no changes were made.
Returns an Enumerator if no block was given.
Returns a new hash created by using environment variable names as values and values as names.
Replaces the contents of the environment variables with the contents of hash.
Re-hashing the environment variables does nothing. It is provided for compatibility with Hash.
Returns true when there are no environment variables
Returns true if there is an environment variable with the given name.
Reads length bytes from ARGF. The files named on the command line are concatenated and treated as a single file by this method, so when called without arguments the contents of this pseudo file are returned in their entirety.
length must be a non-negative integer or nil.
If length is a positive integer, read tries to read length bytes without any conversion (binary mode). It returns nil if an EOF is encountered before anything can be read. Fewer than length bytes are returned if an EOF is encountered during the read. In the case of an integer length, the resulting string is always in ASCII-8BIT encoding.
If length is omitted or is nil, it reads until EOF and the encoding conversion is applied, if applicable. A string is returned even if EOF is encountered before any data is read.
If length is zero, it returns an empty string ("").
If the optional outbuf argument is present, it must reference a String, which will receive the data. The outbuf will contain only the received data after the method call even if it is not empty at the beginning.
For example:
$ echo "small" > small.txt $ echo "large" > large.txt $ ./glark.rb small.txt large.txt ARGF.read #=> "small\nlarge" ARGF.read(200) #=> "small\nlarge" ARGF.read(2) #=> "sm" ARGF.read(0) #=> ""
Note that this method behaves like the fread() function in C. This means it retries to invoke read(2) system calls to read data with the specified length. If you need the behavior like a single read(2) system call, consider ARGF#readpartial or ARGF#read_nonblock.
Reads at most maxlen bytes from the ARGF stream.
If the optional outbuf argument is present, it must reference a String, which will receive the data. The outbuf will contain only the received data after the method call even if it is not empty at the beginning.
It raises EOFError on end of ARGF stream. Since ARGF stream is a concatenation of multiple files, internally EOF is occur for each file. ARGF.readpartial returns empty strings for EOFs except the last one and raises EOFError for the last one.
Reads ARGF‘s current file in its entirety, returning an Array of its lines, one line per element. Lines are assumed to be separated by sep.
lines = ARGF.readlines lines[0] #=> "This is line one\n"
Returns the next line from the current file in ARGF.
By default lines are assumed to be separated by $/; to use a different character as a separator, supply it as a String for the sep argument.
The optional limit argument specifies how many characters of each line to return. By default all characters are returned.
An EOFError is raised at the end of the file.
Reads the next character from ARGF and returns it as a String. Raises an EOFError after the last character of the last file has been read.
For example:
$ echo "foo" > file $ ruby argf.rb file ARGF.readchar #=> "f" ARGF.readchar #=> "o" ARGF.readchar #=> "o" ARGF.readchar #=> "\n" ARGF.readchar #=> end of file reached (EOFError)
Reads the next 8-bit byte from ARGF and returns it as an Integer. Raises an EOFError after the last byte of the last file has been read.
For example:
$ echo "foo" > file $ ruby argf.rb file ARGF.readbyte #=> 102 ARGF.readbyte #=> 111 ARGF.readbyte #=> 111 ARGF.readbyte #=> 10 ARGF.readbyte #=> end of file reached (EOFError)
Positions the current file to the beginning of input, resetting ARGF.lineno to zero.
ARGF.readline #=> "This is line one\n" ARGF.rewind #=> 0 ARGF.lineno #=> 0 ARGF.readline #=> "This is line one\n"
Puts ARGF into binary mode. Once a stream is in binary mode, it cannot be reset to non-binary mode. This option has the following effects:
Newline conversion is disabled.
Encoding conversion is disabled.
Content is treated as ASCII-8BIT.
Returns true if ARGF is being read in binary mode; false otherwise. To enable binary mode use ARGF.binmode.
For example:
ARGF.binmode? #=> false ARGF.binmode ARGF.binmode? #=> true
This method is intended as the primary interface for reading CSV files. You pass a path and any options you wish to set for the read. Each row of file will be passed to the provided block in turn.
The options parameter can be anything CSV::new() understands. This method also understands an additional :encoding parameter that you can use to specify the Encoding of the data in the file to be read. You must provide this unless your data is in Encoding::default_external(). CSV will use this to determine how to parse the data. You may provide a second Encoding to have the data transcoded as it is read. For example, encoding: "UTF-32BE:UTF-8" would read UTF-32BE data from the file but transcode it to UTF-8 before CSV parses it.
Use to slurp a CSV file into an Array of Arrays. Pass the path to the file and any options CSV::new() understands. This method also understands an additional :encoding parameter that you can use to specify the Encoding of the data in the file to be read. You must provide this unless your data is in Encoding::default_external(). CSV will use this to determine how to parse the data. You may provide a second Encoding to have the data transcoded as it is read. For example, encoding: "UTF-32BE:UTF-8" would read UTF-32BE data from the file but transcode it to UTF-8 before CSV parses it.