Ruby stream file io

It returns a File object, so you should be able to call methods like read and readlines. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Open an IO stream from a local file or url Ask Question. Asked 13 years, 2 months ago. Active 4 years, 7 months ago. Viewed 89k times. Is there an easy way to do this in ruby? Improve this question.

Add a comment. On some platforms, such as Windows, non-blocking mode is not supported on IO objects other than sockets. In this case, the read 2 system call is not called. This can be done as follows. Raises an EOFError on end of file. Reads all of the lines in ios , and returns them in an array. Lines are separated by the optional sep. If sep is nil , the rest of the stream is returned as a single record. If the first argument is an integer, or an optional second argument is given, the returning string would not be longer than the given value in bytes.

Its encoding is:. This method is useful for a stream such as a pipe, a socket, or a tty. It blocks only when no data is immediately available. This means that it blocks only when all of the following are true:. The latter means that readpartial is non-blocking-flag insensitive. This may dynamically change the actual class of this stream. The mode and opt parameters accept the same values as IO. Repositions the stream to its beginning, setting both the position and the line number to zero; see Position and Line Number :.

Seeks to the position given by integer offset see Position and constant whence , which is one of:. If single argument is specified, read string from io is tagged with the encoding specified. If two arguments are specified, those must be encoding objects or encoding names, and the first one is the external encoding, and the second one is the internal encoding. Checks if ios starts with a BOM, and then consumes it and sets the external encoding. Returns the result encoding if found, or nil.

If ios is not binmode or its encoding has been set already, an exception will be raised. Returns status information for ios as an object of type File::Stat. Returns the current sync mode of the stream.

When sync mode is true, all output is immediately flushed to the underlying operating system and is not buffered by Ruby internally. See also fsync. Reads maxlen bytes from ios using a low-level read and returns them as a string. Do not mix with other methods that read from ios or you may get unpredictable results.

Seeks to a given offset in the stream according to the value of whence see IO seek for values of whence. Returns the new offset into the file. Writes the given string to ios using a low-level write. Do not mix with other methods that write to ios or you may get unpredictable results. Raises SystemCallError on error. Pushes back bytes passed as a parameter onto ios , such that a subsequent buffered read will return it. It is only guaranteed to support a single byte, and only if ungetbyte or ungetc has not already been called on ios since the previous read of at least a single byte from ios.

However, it can support additional bytes if there is space in the internal buffer to allow for it. Calling this method prepends to the existing buffer, even if the method has already been called previously:. Has no effect with unbuffered reads such as IO sysread. Pushes back characters passed as a parameter onto ios , such that a subsequent buffered read will return it. If given an integer, the integer must represent a valid codepoint in the external encoding of ios. The result may also be smaller than string.

The caller should care such errors and partial write. Note that this doesn't guarantee to write all data in string. The length written is reported as result and it should be checked later.

Home Core 3. Home Classes Methods. In Files file. Parent Object. Files History. The Kernel open method can create an IO or File object for these types of arguments: A plain string represents a filename suitable for the underlying operating system. A string equal to " -" will create another Ruby instance as a subprocess. IO cooked IO cooked! This is the second line. This is the third line. EOT File. Whether the stream is positioned at its beginning or its end.

Whether the stream treats data as text-only or binary. The external and internal encodings. Examples: File. If neither is given, the stream defaults to text data. Example: File. Methods to query the position: IO tell and its alias IO pos return the position for an open stream. A new stream is initially has line number 0. Method IO lineno returns the line number. Class IO: Inherits from class Object. Returns whether self auto-closes.

Returns whether self is in binary mode. Returns the close-on-exec flag for self. Returns whether self is closed. This method returns the number of bytes copied. Synonym for IO. If no block is given, an enumerator is returned instead.

Creates a new file for writing if file does not exist. Creates a new file for reading and writing if file does not exist. The following modes must be used separately, and along with one or more of the modes seen above. The following keys are supported: :mode Same as mode parameter :flags Specifies file open flags as integer. See the document of Kernel. However, several more complicated situations exist. Not the best way to use IO. It accepts the following keys: :encoding string or encoding Specifies the encoding of the read string.

Public Instance Methods self click to toggle source. TypeError Either advice was not a Symbol , or one of the other arguments was not an Integer. This list is not exhaustive; other Errno exceptions are also possible. Sets auto-close flag.

Returns true if ios is binmode. Sets a close-on-exec flag. Returns true if ios will be closed on exec. I eof? Raises an exception if the operating system does not support fsync 2. Reads bytes from the stream in binary mode : If maxlen is nil , reads all bytes.

Otherwise reads maxlen bytes, if available. Otherwise reads all bytes. Note that this method is identical to readpartial except the non-blocking flag is set. File io. Contains maxlen bytes from the stream, if available. Otherwise contains all available bytes, if any available. Otherwise is an empty string. This means that it blocks only when all of the following are true: The byte buffer in the stream is empty.

The content of the stream is empty. The stream is not at EOF. When blocked, the method waits for either more data or EOF on the stream: If more data is read, the method returns the data. When not blocked, the method responds immediately: Returns data from the buffer if there is any. Otherwise returns data from the stream if there is any. Note that this method is similar to sysread.

Here is my work-around:. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Ruby's IO. Ask Question. Asked 3 years ago. Active 3 years ago. Viewed times. Improve this question. What exactly are you trying to test here?

Seems like you don't trust core ruby.