2. Common options

Certain options are available in all of these programs. Rather than writing identical descriptions for each of the programs, they are described here. (In fact, every GNU program accepts (or should accept) these options.)

Normally options and operands can appear in any order, and programs act as if all the options appear before any operands. For example, `sort -r passwd -t :' acts like `sort -r -t : passwd', since `:' is an option-argument of `-t'. However, if the POSIXLY_CORRECT environment variable is set, options must appear before operands, unless otherwise specified for a particular command.

Some of these programs recognize the `--help' and `--version' options only when one of them is the sole command line argument.

`--help'

Print a usage message listing all available options, then exit successfully.

`--version'

Print the version number, then exit successfully.

`--'

Delimit the option list. Later arguments, if any, are treated as operands even if they begin with `-'. For example, `sort -- -r' reads from the file named `-r'.

A single `-' is not really an option, though it looks like one. It stands for standard input, or for standard output if that is clear from the context, and it can be used either as an operand or as an option-argument. For example, `sort -o - -' outputs to standard output and reads from standard input, and is equivalent to plain `sort'. Unless otherwise specified, `-' can appear in any context that requires a file name.

2.1 Backup options		-b -S -V, in some programs.
2.2 Block size		BLOCK_SIZE and --block-size, in some programs.
2.3 Target directory		--target-directory, in some programs.
2.4 Trailing slashes		--strip-trailing-slashes, in some programs.
2.5 Standards conformance		Conformance to the POSIX standard.