解读Linux命令格式
环境
Linux HA5-139JK 2.6.18-164.el5 #1 SMP Tue Aug 18 15:51:48 EDT 2009 x86_64 x86_64 x86_64 GNU/Linux
Linux命令很多，但对格式本身解读的文章几乎是空白，都在凭对格式的猜测来写命令，就此在网上搜集此类资料都很少而且很不全面，想找官方的，也没找到。根据自己的理解写一篇出来，希望对初学者有用。
一、命令的一般格式
command [options] [arguments]
command：命令
options：--单词 或 -单字
arguments：参数，有时候选项也带参数。
二、命令格式中的符号含义
在查看命令帮助时，会出现[],<>,|等符号，它们的含义如下：
[] 表示是可选的;
<> 表示可变选项，一般是多选一，而且必须是要选其一。
x|y|z 多选一，如果加上[]，可不选。
-abc 多选，如果加上[]，可不选。
三、常见命令格式的举例说明
对于命令格式中常常可以看到如下的格式：
1、[ --atime-preserve ]，表示一个可选选项。
2、[ -B, --read-full-records ]，表示一个可选选项，简写为-B，完整写法是--read-full-records，两者在用的时候只能选择其一，它们的功能都是完全一样的。一般带“-”开头的选项都是简写，“--”开头的命令都是完整写法，并且，一般的选择都有一个简写，一个完整写法，简写写在前面，完整写法写在后面，中间用逗号分割。
3、[ -b, --blocking-factor N ]，表示一个可选选项，简写为-b N，完整写法是--blocking-factor N，N代表这个参数需要一个值，在详细描述中可以看到。当然，选项可以带参数，也可以不带参数，大部分选项是没有参数的，相当于控制开关。命令的书写如：tar -b=10000 -cvf com.tar.gz com
4、[ -F, --info-script F --new-volume-script F ]，表示有两个同时存在的可选命令，-F F --new-volume-script F，两个选项必须同时出现，在此，后面的选项没有简写。
5、[ -z, --gzip, --gunzip, --ungzip ]，表示一个可选选项，它的写法有多种，除了-z之外，其他的都是它的完整写法。
6、[ -[0-7][lmh] ]，表示嵌套的可选选项，0-7表示取值从0到7取一个。
四、通过tar命令行来解读Unix命令：
[kf139@HA5-139JK bin]$ man tar
TAR(1) tar TAR(1)
NAME（名称）
tar - The GNU version of the tar archiving utility
SYNOPSIS（大纲）
tar <operation> [options]
Operations:（操作选项）
[-]A --catenate --concatenate
[-]c --create
[-]d --diff --compare
[-]r --append
[-]t --list
[-]u --update
[-]x --extract --get
--delete
Common Options:（公共选项）
-C, --directory DIR
-f, --file F
-j, --bzip2
-p, --preserve-permissions
-v, --verbose
-z, --gzip
All Options:（所有选项）
[ --atime-preserve ] [ -b, --blocking-factor N ] [ -B, --read-full-records ] [ --backup BACKUP-TYPE ] [ --block-compress ] [ -C,
--directory DIR ] [ --check-links ] [ --checkpoint ] [ -f, --file [HOSTNAME:]F ] [ -F, --info-script F --new-volume-script F ] [
--force-local ] [ --format FORMAT ] [ -g, --listed-incremental F ] [ -G, --incremental ] [ --group GROUP ] [ -h, --dereference ] [
--help ] [ -i, --ignore-zeros ] [ --ignore-case ] [ --ignore-failed-read ] [ --index-file FILE ] [ -j, --bzip2 ] [ -k, --keep-old-
files ] [ -K, --starting-file F ] [ --keep-newer-files ] [ -l, --one-file-system ] [ -L, --tape-length N ] [ -m, --touch, --modifica-
tion-time ] [ -M, --multi-volume ] [ --mode PERMISSIONS ] [ -N, --after-date DATE, --newer DATE ] [ --newer-mtime DATE ] [ --no-
anchored ] [ --no-ignore-case ] [ --no-recursion ] [ --no-same-permissions ] [ --no-wildcards ] [ --no-wildcards-match-slash ] [
--null ] [ --numeric-owner ] [ -o, --old-archive, --portability, --no-same-owner ] [ -O, --to-stdout ] [ --occurrence NUM ] [
--overwrite ] [ --overwrite-dir ] [ --owner USER ] [ -p, --same-permissions, --preserve-permissions ] [ -P, --absolute-names ] [
--pax-option KEYWORD-LIST ] [ --posix ] [ --preserve ] [ --acls ] [ --selinux ] [ --xattrs ] [ --no-acls ] [ --no-selinux ] [ --no-
xattrs ] [ -R, --block-number ] [ --record-size SIZE ] [ --recursion ] [ --recursive-unlink ] [ --remove-files ] [ --rmt-command CMD ]
[ --rsh-command CMD ] [ -s, --same-order, --preserve-order ] [ -S, --sparse ] [ --same-owner ] [ --show-defaults ] [ --show-omitted-
dirs ] [ --strip-components NUMBER, --strip-path NUMBER (1) ] [ --suffix SUFFIX ] [ -T, --files-from F ] [ --totals ] [ -U,
--unlink-first ] [ --use-compress-program PROG ] [ --utc ] [ -v, --verbose ] [ -V, --label NAME ] [ --version ] [ --volno-file F ] [
-w, --interactive, --confirmation ] [ -W, --verify ] [ --wildcards ] [ --wildcards-match-slash ] [ --exclude PATTERN ] [ -X,
--exclude-from FILE ] [ -Z, --compress, --uncompress ] [ -z, --gzip, --gunzip, --ungzip ] [ -[0-7][lmh] ]
(1) tar-1.14 uses --strip-path, tar-1.14.90+ uses --strip-components
DESCRIPTION（描述）
This manual page documents the GNU version of tar, an archiving program designed to store and extract files from an archive file known
as a tarfile. A tarfile may be made on a tape drive, however, it is also common to write a tarfile to a normal file. The first argu-
ment to tar must be one of the options Acdrtux, followed by any optional functions. The final arguments to tar are the names of the
files or directories which should be archived. The use of a directory name always implies that the subdirectories below should be
included in the archive.
EXAMPLES（例子）
tar -xvf foo.tar
verbosely extract foo.tar
tar -xzf foo.tar.gz
extract gzipped foo.tar.gz
tar -cjf foo.tar.bz2 bar/
create bzipped tar archive of the directory bar called foo.tar.bz2
tar -xjf foo.tar.bz2 -C bar/
extract bzipped foo.tar.bz2 after changing directory to bar
tar -xzf foo.tar.gz blah.txt
extract the file blah.txt from foo.tar.gz
FUNCTION LETTERS（功能选项）
One of the following options must be used:
-A, --catenate, --concatenate
append tar files to an archive
-c, --create
create a new archive
-d, --diff, --compare
find differences between archive and file system
-r, --append
append files to the end of an archive
-t, --list
list the contents of an archive
-u, --update
only append files that are newer than the existing in archive
-x, --extract, --get
extract files from an archive
--delete
delete from the archive (not for use on mag tapes!)
COMMON OPTIONS（公共选项）
-C, --directory DIR
change to directory DIR
-f, --file [HOSTNAME:]F
use archive file or device F (default "-", meaning stdin/stdout)
-j, --bzip2
filter archive through bzip2, use to decompress .bz2 files
-p, --preserve-permissions
extract all protection information
-v, --verbose
verbosely list files processed
-z, --gzip, --ungzip
filter the archive through gzip
ALL OPTIONS（所有选项）
--atime-preserve
don’t change access times on dumped files
-b, --blocking-factor N
block size of Nx512 bytes (default N=20)
-B, --read-full-blocks
reblock as we read (for reading 4.2BSD pipes)
--backup BACKUP-TYPE
backup files instead of deleting them using BACKUP-TYPE simple or numbered
--block-compress
block the output of compression program for tapes
-C, --directory DIR
change to directory DIR
--check-links
warn if number of hard links to the file on the filesystem mismatch the number of links recorded in the archive
--checkpoint
print directory names while reading the archive
-f, --file [HOSTNAME:]F
use archive file or device F (default "-", meaning stdin/stdout)
-F, --info-script F --new-volume-script F
run script at end of each tape (implies --multi-volume)
--force-local
archive file is local even if has a colon
--format FORMAT
selects output archive format
v7 - Unix V7
oldgnu - GNU tar <=1.12
gnu - GNU tar 1.13
ustar - POSIX.1-1988
posix - POSIX.1-2001
-g, --listed-incremental F
create/list/extract new GNU-format incremental backup
-G, --incremental
create/list/extract old GNU-format incremental backup
-h, --dereference
don’t dump symlinks; dump the files they point to
--help like this manpage, but not as cool
-i, --ignore-zeros
ignore blocks of zeros in archive (normally mean EOF)
--ignore-case
ignore case when excluding files
--ignore-failed-read
don’t exit with non-zero status on unreadable files
--index-file FILE
send verbose output to FILE instead of stdout
-j, --bzip2
filter archive through bzip2, use to decompress .bz2 files
-k, --keep-old-files
keep existing files; don’t overwrite them from archive
-K, --starting-file F
begin at file F in the archive
--keep-newer-files
do not overwrite files which are newer than the archive
-l, --one-file-system
stay in local file system when creating an archive
-L, --tape-length N
change tapes after writing N*1024 bytes
-m, --touch, --modification-time
don’t extract file modified time
-M, --multi-volume
create/list/extract multi-volume archive
--mode PERMISSIONS
apply PERMISSIONS while adding files (see chmod(1))
-N, --after-date DATE, --newer DATE
only store files newer than DATE
--newer-mtime DATE
like --newer, but with a DATE
--no-anchored
match any subsequenceof the name’s components with --exclude
--no-ignore-case
use case-sensitive matching with --exclude
--no-recursion
don’t recurse into directories
--no-same-permissions
apply user’s umask when extracting files instead of recorded permissions
--no-wildcards
don’t use wildcards with --exclude
--no-wildcards-match-slash
wildcards do not match slashes (/) with --exclude
--null --files-from reads null-terminated names, disable --directory
--numeric-owner
always use numbers for user/group names
-o, --old-archive, --portability
like --format=v7; -o exhibits this behavior when creating an archive (deprecated behavior)
-o, --no-same-owner
do not attempt to restore ownership when extracting; -o exhibits this behavior when extracting an archive
-O, --to-stdout
extract files to standard output
--occurrence NUM
process only NUM occurrences of each named file; used with --delete, --diff, --extract, or --list
--overwrite
overwrite existing files and directory metadata when extracting
--overwrite-dir
overwrite directory metadata when extracting
--owner USER
change owner of extraced files to USER
-p, --same-permissions, --preserve-permissions
extract all protection information
-P, --absolute-names
don’t strip leading ‘/’s from file names
--pax-option KEYWORD-LIST
used only with POSIX.1-2001 archives to modify the way tar handles extended header keywords
--posix
like --format=posix
--preserve
like --preserve-permissions --same-order
--acls this option causes tar to store each file’s ACLs in the archive.
--selinux
this option causes tar to store each file’s SELinux security context information in the archive.
--xattrs
this option causes tar to store each file’s extended attributes in the archive. This option also enables --acls and--selinux if
they haven’t been set already, due to the fact that the data for those are stored in special xattrs.
--no-acls
This option causes tar not to store each file’s ACLs in the archive and not to extract any ACL information in an archive.
--no-selinux
this option causes tar not to store each file’s SELinux security context information in the archive and not to extract any
SELinux information in an archive.
--no-xattrs
this option causes tar not to store each file’s extended attributes in the archive and not to extract any extended attributes
in an archive. This option also enables --no-acls and --no-selinux if they haven’t been set already.
-R, --record-number
show record number within archive with each message
--record-size SIZE
use SIZE bytes per record when accessing archives
--recursion
recurse into directories
--recursive-unlink
remove existing directories before extracting directories of the same name
--remove-files
remove files after adding them to the archive
--rmt-command CMD
use CMD instead of the default /usr/sbin/rmt
--rsh-command CMD
use remote CMD instead of rsh(1)
-s, --same-order, --preserve-order
list of names to extract is sorted to match archive
-S, --sparse
handle sparse files efficiently
--same-owner
create extracted files with the same ownership
--show-defaults
display the default options used by tar
--show-omitted-dirs
print directories tar skips while operating on an archive
--strip-components NUMBER, --strip-path NUMBER
strip NUMBER of leading components from file names before extraction
(1) tar-1.14 uses --strip-path, tar-1.14.90+ uses --strip-components
--suffix SUFFIX
use SUFFIX instead of default ’~’ when backing up files
-T, --files-from F
get names to extract or create from file F
--totals
print total bytes written with --create
-U, --unlink-first
remove existing files before extracting files of the same name
--use-compress-program PROG
access the archive through PROG which is generally a compression program
--utc display file modification dates in UTC
-v, --verbose
verbosely list files processed
-V, --label NAME
create archive with volume name NAME
--version
print tar program version number
--volno-file F
keep track of which volume of a multi-volume archive its working in FILE; used with --multi-volume
-w, --interactive, --confirmation
ask for confirmation for every action
-W, --verify
attempt to verify the archive after writing it
--wildcards
use wildcards with --exclude
--wildcards-match-slash
wildcards match slashes (/) with --exclude
--exclude PATTERN
exclude files based upon PATTERN
-X, --exclude-from FILE
exclude files listed in FILE
-Z, --compress, --uncompress
filter the archive through compress
-z, --gzip, --gunzip, --ungzip
filter the archive through gzip
--use-compress-program PROG
filter the archive through PROG (which must accept -d)
-[0-7][lmh]
specify drive and density
BUGS（缺陷）
The GNU folks, in general, abhor man pages, and create info documents instead. The maintainer of tar falls into this category. Thus
this man page may not be complete, nor current, and was included in the Red Hat CVS tree because man is a great tool :). This man
page was first taken from Debian Linux and has since been loving updated here.
REPORTING BUGS（报道中的缺陷）
Please report bugs via https://bugzilla.redhat.com
SEE ALSO（参考）
The full documentation for tar is maintained as a Texinfo manual. If the info and tar programs are properly installed at your site,
the command
info tar
should give you access to the complete manual.
AUTHORS（作者）
Debian Linux http://www.debian.org/
Mike Frysinger <vapier@gentoo.org>
GNU Oct 2004 TAR(1)
上面的tar命令用法很复杂，可以看个简单的rm删除命令：
[kf139@HA5-139JK bin]$ man rm
RM(1) User Commands RM(1)
NAME
rm - remove files or directories
SYNOPSIS
rm [OPTION]... FILE...
DESCRIPTION
This manual page documents the GNU version of rm. rm removes each specified file. By default, it does not remove directories.
If a file is unwritable, the standard input is a tty, and the -f or --force option is not given, rm prompts the user for whether to
remove the file. If the response is not affirmative, the file is skipped.
OPTIONS
Remove (unlink) the FILE(s).
-f, --force
ignore nonexistent files, never prompt
-i, --interactive
prompt before any removal
--no-preserve-root do not treat ‘/’ specially (the default)
--preserve-root
fail to operate recursively on ‘/’
-r, -R, --recursive
remove directories and their contents recursively
-v, --verbose
explain what is being done
--help display this help and exit
--version
output version information and exit
By default, rm does not remove directories. Use the --recursive (-r or -R) option to remove each listed directory, too, along with
all of its contents.
To remove a file whose name starts with a ‘-’, for example ‘-foo’, use one of these commands:
rm -- -foo
rm ./-foo
Note that if you use rm to remove a file, it is usually possible to recover the contents of that file. If you want more assurance
that the contents are truly unrecoverable, consider using shred.
AUTHOR
Written by Paul Rubin, David MacKenzie, Richard Stallman, and Jim Meyering.
REPORTING BUGS
Report bugs to <bug-coreutils@gnu.org>.
COPYRIGHT
Copyright (C) 2006 Free Software Foundation, Inc.
This is free software. You may redistribute copies of it under the terms of the GNU General Public License
<http://www.gnu.org/licenses/gpl.html>. There is NO WARRANTY, to the extent permitted by law.
SEE ALSO
chattr(1), shred(1)
The full documentation for rm is maintained as a Texinfo manual. If the info and rm programs are properly installed at your site, the
command
info rm
should give you access to the complete manual.
rm 5.97 July 2009 RM(1)
五、Linux命令和Unix命令格式大致都一样，不同的系统，命令也可能不同。有些命令虽然选项很多，但不一定全支持。用的时候还是多试试为好，实践才是最可靠的检验标准，本文旨在让初学者能快速看懂man打印出命令帮助。欢迎拍砖！
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