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)
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.
A few programs can usefully have trailing operands with leading `-'.
With such a program, options must precede operands even if
`POSIXLY_CORRECT' is not set, and this fact is noted in the program
description. For example, the `env' command's options must appear
before its operands, since in some cases the operands specify a command
that itself contains options.
Most programs that accept long options recognize unambiguous
abbreviations of those options. For example, `rmdir
--ignore-fail-on-non-empty' can be invoked as `rmdir --ignore-fail' or
even `rmdir --i'. Ambiguous options, such as `ls --h', are identified
Some of these programs recognize the `--help' and `--version'
options only when one of them is the sole command line argument. For
these programs, abbreviations of the long options are not always
Print a usage message listing all available options, then exit
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 `-' operand 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. For example, `sort -' reads from standard
input, and is equivalent to plain `sort', and `tee -' writes an extra
copy of its input to standard output. Unless otherwise specified, `-'
can appear as any operand that requires a file name.
- Exit status
- Indicating program success or failure.
- Backup options
- -b -S, in some programs.
- Block size
- BLOCK_SIZE and --block-size, in some programs.
- Signal specifications
- Specifying signals using the --signal option.
- Disambiguating names and IDs
- chgrp and chown owner and group syntax
- Random sources
- --random-source, in some programs.
- Target directory
- Specifying a target directory, in some programs.
- Trailing slashes
- --strip-trailing-slashes, in some programs.
- Traversing symlinks
- -H, -L, or -P, in some programs.
- Treating / specially
- --preserve-root and --no-preserve-root.
- Special built-in utilities
- `break', `:', `eval', ...
- Standards conformance
- Conformance to the POSIX standard.
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