org.unix4j.unix

Class Head

java.lang.Object

org.unix4j.unix.Head

public final class Head
extends Object

Non-instantiable module with inner types making up the head command.

NAME

head - display first lines of a file

SYNOPSIS

	head
	head <args>
	head <count>
	head [-cq] <count>
	head <files>
	head <inputs>
	head <count> <files>
	head <count> <paths>
	head <count> <inputs>
	head [-cq] <count> <files>
	head [-cq] <count> <paths>
	head [-cq] <count> <inputs>

See Head.Interface for the corresponding command signature methods.

DESCRIPTION

This filter displays the first count lines or characters of each of the specified files, or of the standard input if no files are specified. If count is omitted it defaults to 10. Both line and character counts start from 1.

If more than a single file is specified, each file is preceded by a header consisting of the string "==> XXX <==" where "XXX" is the name of the file.

Options

The following options are supported:

	-c		--chars		The count argument is in units of characters instead of lines. Starts from 1 and includes line ending characters.
	-q		--suppressHeaders		Suppresses printing of headers when multiple files are being examined.

OPERANDS

The following operands are supported:

	<count>	:	long		The first count lines of each input file are copied to standard output, starting from 1 (characters instead of lines if the -c option is specified). Must be a non-negative integer or an exception is thrown. If count is greater than the number number of lines (characters) in the input, the application will not error and send the whole file to the output.
	<paths>	:	String...		Path names of the input files to be filtered; wildcards * and ? are supported; relative paths are resolved on the basis of the current working directory.
	<files>	:	java.io.File...		The input files to be filtered; relative paths are not resolved (use the string paths argument to enable relative path resolving based on the current working directory).
	<inputs>	:	org.unix4j.io.Input...		The inputs to be filtered.
	<args>	:	String...		String arguments defining the options and operands for the command. Options can be specified by acronym (with a leading dash "-") or by long name (with two leading dashes "--"). Operands other than the default "--paths" operand have to be prefixed with the operand name (e.g. "--count" for a subsequent count operand value).
	<options>	:	HeadOptions		Options for the head command.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	Head.Interface<R> Interface defining all method signatures for the "head" command.

Field Summary

Fields

Modifier and Type	Field and Description
static HeadFactory	Factory Singleton factory instance for the "head" command.
static String	NAME The "head" command name.
static HeadOptionSets	Options Options for the "head" command: c, q.

Method Summary

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

NAME

public static final String NAME

The "head" command name.

See Also:

Constant Field Values

Options

public static final HeadOptionSets Options

Options for the "head" command: c, q.

	-c		--chars		The count argument is in units of characters instead of lines. Starts from 1 and includes line ending characters.
	-q		--suppressHeaders		Suppresses printing of headers when multiple files are being examined.

Factory

public static final HeadFactory Factory

Singleton factory instance for the "head" command.