touch 命令
用途：新建一个或多个空文件或更改已存在文件的时间戳
格式：touch 文件名
file 命令
用途：查看文件或目录类型
格式：file 文件名
stat 命令
用途：查看文件或目录详细属性
格式：stat 文件或目录名
在根目录下新建文件itkaifang并查看其属性
[root@itkaifang ~]# touch /itkaifang [root@itkaifang ~]# ls / a b boot dev f home lib lost+found lv-D misc net proc sbin soft sys tmp usr a.txt bin c etc haha itkaifang lib64 lv-C media mnt opt root selinux srv tftpboot u01 var [root@itkaifang ~]# stat /itkaifang File: `/itkaifang' Size: 0 Blocks: 0 IO Block: 4096 regular empty file Device: 803h/2051d Inode: 98116 Links: 1 Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) Access: 2017-02-26 16:48:31.000000000 +0800 Modify: 2017-02-26 16:48:31.000000000 +0800 Change: 2017-02-26 16:48:31.000000000 +0800
更新itkaifang文件的时间戳
[root@itkaifang ~]# touch /itkaifang [root@itkaifang ~]# stat /itkaifang File: `/itkaifang' Size: 0 Blocks: 0 IO Block: 4096 regular empty file Device: 803h/2051d Inode: 98116 Links: 1 Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) Access: 2017-02-26 16:51:38.000000000 +0800 Modify: 2017-02-26 16:51:38.000000000 +0800 Change: 2017-02-26 16:51:38.000000000 +0800
查看itkaifang文件类型
[root@itkaifang ~]# file /itkaifang /itkaifang: ASCII text
man touch 内部命令文档
TOUCH(1) User Commands TOUCH(1) NAME touch - change file timestamps SYNOPSIS touch [OPTION]... FILE... DESCRIPTION Update the access and modification times of each FILE to the current time. Mandatory arguments to long options are mandatory for short options too. -a change only the access time -c, --no-create do not create any files -d, --date=STRING parse STRING and use it instead of current time -f (ignored) -m change only the modification time -r, --reference=FILE use this file’s times instead of current time -t STAMP use [[CC]YY]MMDDhhmm[.ss] instead of current time --time=WORD change the specified time: WORD is access, atime, or use: equivalent to -a WORD is modify or mtime: equiva- lent to -m --help display this help and exit --version output version information and exit Note that the -d and -t options accept different time-date formats. If a FILE is -, touch standard output. AUTHOR Written by Paul Rubin, Arnold Robbins, Jim Kingdon, David MacKenzie, and Randy Smith. REPORTING BUGS Report bugs to <bug-coreutils@gnu.org>. COPYRIGHT Copyright © 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 The full documentation for touch is maintained as a Texinfo manual. If the info and touch programs are properly installed at your site, the command info touch should give you access to the complete manual. touch 5.97 February 2010 TOUCH(1)
man file 内部命令文档
FILE(1) FILE(1)
NAME
file - determine file type
SYNOPSIS
file [ -bchikLnNprsvz ] [ -f namefile ] [ -F separator ] [ -m magicfiles ] file ...
file -C [ -m magicfile ]
DESCRIPTION
This manual page documents version 4.17 of the file command.
File tests each argument in an attempt to classify it. There are three sets of tests, performed in this order:
filesystem tests, magic number tests, and language tests. The first test that succeeds causes the file type to be
printed.
The type printed will usually contain one of the words text (the file contains only printing characters and a few
common control characters and is probably safe to read on an ASCII terminal), executable (the file contains the
result of compiling a program in a form understandable to some UNIX kernel or another), or data meaning anything
else (data is usually ‘binary’ or non-printable). Exceptions are well-known file formats (core files, tar
archives) that are known to contain binary data. When modifying the file /usr/share/file/magic or the program
itself, preserve these keywords . People depend on knowing that all the readable files in a directory have the
word ‘‘text’’ printed. Don’t do as Berkeley did and change ‘‘shell commands text’’ to ‘‘shell script’’. Note that
the file /usr/share/file/magic is built mechanically from a large number of small files in the subdirectory Magdir
in the source distribution of this program.
The filesystem tests are based on examining the return from a stat(2) system call. The program checks to see if
the file is empty, or if it’s some sort of special file. Any known file types appropriate to the system you are
running on (sockets, symbolic links, or named pipes (FIFOs) on those systems that implement them) are intuited if
they are defined in the system header file <sys/stat.h>.
The magic number tests are used to check for files with data in particular fixed formats. The canonical example of
this is a binary executable (compiled program) a.out file, whose format is defined in a.out.h and possibly exec.h
in the standard include directory. These files have a ‘magic number’ stored in a particular place near the begin-
ning of the file that tells the UNIX operating system that the file is a binary executable, and which of several
types thereof. The concept of ‘magic number’ has been applied by extension to data files. Any file with some
invariant identifier at a small fixed offset into the file can usually be described in this way. The information
identifying these files is read from the compiled magic file /usr/share/file/magic.mgc , or /usr/share/file/magic
if the compile file does not exist. In addition file will look in $HOME/.magic.mgc , or $HOME/.magic for magic
entries.
If a file does not match any of the entries in the magic file, it is examined to see if it seems to be a text file.
ASCII, ISO-8859-x, non-ISO 8-bit extended-ASCII character sets (such as those used on Macintosh and IBM PC sys-
tems), UTF-8-encoded Unicode, UTF-16-encoded Unicode, and EBCDIC character sets can be distinguished by the differ-
ent ranges and sequences of bytes that constitute printable text in each set. If a file passes any of these tests,
its character set is reported. ASCII, ISO-8859-x, UTF-8, and extended-ASCII files are identified as ‘‘text’’
because they will be mostly readable on nearly any terminal; UTF-16 and EBCDIC are only ‘‘character data’’ because,
while they contain text, it is text that will require translation before it can be read. In addition, file will
attempt to determine other characteristics of text-type files. If the lines of a file are terminated by CR, CRLF,
or NEL, instead of the Unix-standard LF, this will be reported. Files that contain embedded escape sequences or
overstriking will also be identified.
Once file has determined the character set used in a text-type file, it will attempt to determine in what language
the file is written. The language tests look for particular strings (cf names.h) that can appear anywhere in the
first few blocks of a file. For example, the keyword .br indicates that the file is most likely a troff(1) input
file, just as the keyword struct indicates a C program. These tests are less reliable than the previous two
groups, so they are performed last. The language test routines also test for some miscellany (such as tar(1)
archives).
Any file that cannot be identified as having been written in any of the character sets listed above is simply said
to be ‘‘data’’.
OPTIONS
-b, --brief
Do not prepend filenames to output lines (brief mode).
-c, --checking-printout
Cause a checking printout of the parsed form of the magic file. This is usually used in conjunction with
-m to debug a new magic file before installing it.
-C, --compile
Write a magic.mgc output file that contains a pre-parsed version of file.
-f, --files-from namefile
Read the names of the files to be examined from namefile (one per line) before the argument list. Either
namefile or at least one filename argument must be present; to test the standard input, use ‘‘-’’ as a
filename argument.
-F, --separator separator
Use the specified string as the separator between the filename and the file result returned. Defaults to
‘‘:’’.
-h, --no-dereference
option causes symlinks not to be followed (on systems that support symbolic links). This is the default if
the environment variable POSIXLY_CORRECT is not defined.
-i, --mime
Causes the file command to output mime type strings rather than the more traditional human readable ones.
Thus it may say ‘‘text/plain; charset=us-ascii’’ rather than ‘‘ASCII text’’. In order for this option to
work, file changes the way it handles files recognised by the command itself (such as many of the text file
types, directories etc), and makes use of an alternative ‘‘magic’’ file. (See ‘‘FILES’’ section, below).
-k, --keep-going
Don’t stop at the first match, keep going.
-L, --dereference
option causes symlinks to be followed, as the like-named option in ls(1) (on systems that support symbolic
links). This is the default if the environment variable POSIXLY_CORRECT is defined.
-m, --magic-file list
Specify an alternate list of files containing magic numbers. This can be a single file, or a colon-sepa-
rated list of files. If a compiled magic file is found alongside, it will be used instead. With the -i or
--mime option, the program adds ".mime" to each file name.
-n, --no-buffer
Force stdout to be flushed after checking each file. This is only useful if checking a list of files. It
is intended to be used by programs that want filetype output from a pipe.
-N, --no-pad
Don’t pad filenames so that they align in the output.
-p, --preserve-date
On systems that support utime(2) or utimes(2), attempt to preserve the access time of files analyzed, to
pretend that file(2) never read them.
-r, --raw
Don’t translate unprintable characters to \ooo. Normally file translates unprintable characters to their
octal representation.
-s, --special-files
Normally, file only attempts to read and determine the type of argument files which stat(2) reports are
ordinary files. This prevents problems, because reading special files may have peculiar consequences.
Specifying the -s option causes file to also read argument files which are block or character special
files. This is useful for determining the filesystem types of the data in raw disk partitions, which are
block special files. This option also causes file to disregard the file size as reported by stat(2) since
on some systems it reports a zero size for raw disk partitions.
-v, --version
Print the version of the program and exit.
-z, --uncompress
Try to look inside compressed files.
--help Print a help message and exit.
FILES
/usr/share/file/magic.mgc
Default compiled list of magic numbers
/usr/share/file/magic
Default list of magic numbers
/usr/share/file/magic.mime.mgc
Default compiled list of magic numbers, used to output mime types when the -i option is specified.
/usr/share/file/magic.mime
Default list of magic numbers, used to output mime types when the -i option is specified.
ENVIRONMENT
The environment variable MAGIC can be used to set the default magic number file name. If that variable is set,
then file will not attempt to open $HOME/.magic . file adds ".mime" and/or ".mgc" to the value of this variable as
appropriate. The environment variable POSIXLY_CORRECT controls (on systems that support symbolic links), if file
will attempt to follow symlinks or not. If set, then file follows symlink, otherwise it does not. This is also con-
trolled by the L and h options.
SEE ALSO
magic(5) - description of magic file format.
strings(1), od(1), hexdump(1) - tools for examining non-textfiles.
STANDARDS CONFORMANCE
This program is believed to exceed the System V Interface Definition of FILE(CMD), as near as one can determine
from the vague language contained therein. Its behaviour is mostly compatible with the System V program of the
same name. This version knows more magic, however, so it will produce different (albeit more accurate) output in
many cases.
The one significant difference between this version and System V is that this version treats any white space as a
delimiter, so that spaces in pattern strings must be escaped. For example,
>10 string language impress (imPRESS data)
in an existing magic file would have to be changed to
>10 string language\ impress (imPRESS data)
In addition, in this version, if a pattern string contains a backslash, it must be escaped. For example
0 string \begindata Andrew Toolkit document
in an existing magic file would have to be changed to
0 string \\begindata Andrew Toolkit document
SunOS releases 3.2 and later from Sun Microsystems include a file(1) command derived from the System V one, but
with some extensions. My version differs from Sun’s only in minor ways. It includes the extension of the ‘&’
operator, used as, for example,
>16 long&0x7fffffff >0 not stripped
MAGIC DIRECTORY
The magic file entries have been collected from various sources, mainly USENET, and contributed by various authors.
Christos Zoulas (address below) will collect additional or corrected magic file entries. A consolidation of magic
file entries will be distributed periodically.
The order of entries in the magic file is significant. Depending on what system you are using, the order that they
are put together may be incorrect. If your old file command uses a magic file, keep the old magic file around for
comparison purposes (rename it to /usr/share/file/magic.orig).
EXAMPLES
$ file file.c file /dev/{wd0a,hda}
file.c: C program text
file: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV),
dynamically linked (uses shared libs), stripped
/dev/wd0a: block special (0/0)
/dev/hda: block special (3/0)
$ file -s /dev/wd0{b,d}
/dev/wd0b: data
/dev/wd0d: x86 boot sector
$ file -s /dev/hda{,1,2,3,4,5,6,7,8,9,10}
/dev/hda: x86 boot sector
/dev/hda1: Linux/i386 ext2 filesystem
/dev/hda2: x86 boot sector
/dev/hda3: x86 boot sector, extended partition table
/dev/hda4: Linux/i386 ext2 filesystem
/dev/hda5: Linux/i386 swap file
/dev/hda6: Linux/i386 swap file
/dev/hda7: Linux/i386 swap file
/dev/hda8: Linux/i386 swap file
/dev/hda9: empty
/dev/hda10: empty
$ file -i file.c file /dev/{wd0a,hda}
file.c: text/x-c
file: application/x-executable, dynamically linked (uses shared libs),
not stripped
/dev/hda: application/x-not-regular-file
HISTORY
There has been a file command in every UNIX since at least Research Version 4 (man page dated November, 1973). The
System V version introduced one significant major change: the external list of magic number types. This slowed the
program down slightly but made it a lot more flexible.
This program, based on the System V version, was written by Ian Darwin <ian@darwinsys.com> without looking at any-
body else’s source code.
John Gilmore revised the code extensively, making it better than the first version. Geoff Collyer found several
inadequacies and provided some magic file entries. Contributions by the ‘&’ operator by Rob McMahon, cudcv@war-
wick.ac.uk, 1989.
Guy Harris, guy@netapp.com, made many changes from 1993 to the present.
Primary development and maintenance from 1990 to the present by Christos Zoulas (christos@astron.com).
Altered by Chris Lowth, chris@lowth.com, 2000: Handle the ‘‘-i’’ option to output mime type strings and using an
alternative magic file and internal logic.
Altered by Eric Fischer (enf@pobox.com), July, 2000, to identify character codes and attempt to identify the lan-
guages of non-ASCII files.
The list of contributors to the "Magdir" directory (source for the /usr/share/file/magic file) is too long to
include here. You know who you are; thank you.
LEGAL NOTICE
Copyright (c) Ian F. Darwin, Toronto, Canada, 1986-1999. Covered by the standard Berkeley Software Distribution
copyright; see the file LEGAL.NOTICE in the source distribution.
The files tar.h and is_tar.c were written by John Gilmore from his public-domain tar program, and are not covered
by the above license.
BUGS
There must be a better way to automate the construction of the Magic file from all the glop in magdir. What is it?
Better yet, the magic file should be compiled into binary (say, ndbm(3) or, better yet, fixed-length ASCII strings
for use in heterogenous network environments) for faster startup. Then the program would run as fast as the Ver-
sion 7 program of the same name, with the flexibility of the System V version.
File uses several algorithms that favor speed over accuracy, thus it can be misled about the contents of text
files.
The support for text files (primarily for programming languages) is simplistic, inefficient and requires recompila-
tion to update.
There should be an ‘‘else’’ clause to follow a series of continuation lines.
The magic file and keywords should have regular expression support. Their use of ASCII TAB as a field delimiter is
ugly and makes it hard to edit the files, but is entrenched.
It might be advisable to allow upper-case letters in keywords for e.g., troff(1) commands vs man page macros. Reg-
ular expression support would make this easy.
The program doesn’t grok FORTRAN. It should be able to figure FORTRAN by seeing some keywords which appear
indented at the start of line. Regular expression support would make this easy.
The list of keywords in ascmagic probably belongs in the Magic file. This could be done by using some keyword like
‘*’ for the offset value.
Another optimisation would be to sort the magic file so that we can just run down all the tests for the first byte,
first word, first long, etc, once we have fetched it. Complain about conflicts in the magic file entries. Make a
rule that the magic entries sort based on file offset rather than position within the magic file?
The program should provide a way to give an estimate of ‘‘how good’’ a guess is. We end up removing guesses (e.g.
‘‘From ’’ as first 5 chars of file) because they are not as good as other guesses (e.g. ‘‘Newsgroups:’’ versus
‘‘Return-Path:’’). Still, if the others don’t pan out, it should be possible to use the first guess.
This program is slower than some vendors’ file commands. The new support for multiple character codes makes it
even slower.
This manual page, and particularly this section, is too long.
AVAILABILITY
You can obtain the original author’s latest version by anonymous FTP on ftp.astron.com in the directory
/pub/file/file-X.YZ.tar.gz
Copyright but distributable FILE(1)man stat 内部命令文档
STAT(1) User Commands STAT(1) NAME stat - display file or file system status SYNOPSIS stat [OPTION] FILE... DESCRIPTION Display file or file system status. -L, --dereference follow links -Z, --context print the security context information if available -f, --file-system display file system status instead of file status -c --format=FORMAT use the specified FORMAT instead of the default; output a newline after each use of FORMAT --printf=FORMAT like --format, but interpret backslash escapes, and do not output a mandatory trailing newline. If you want a newline, include \n in FORMAT. -t, --terse print the information in terse form --help display this help and exit --version output version information and exit The valid format sequences for files (without --file-system): %a Access rights in octal %A Access rights in human readable form %b Number of blocks allocated (see %B) %B The size in bytes of each block reported by %b %d Device number in decimal %D Device number in hex %f Raw mode in hex %F File type %g Group ID of owner %G Group name of owner %h Number of hard links %i Inode number %n File name %N Quoted file name with dereference if symbolic link %o I/O block size %s Total size, in bytes %t Major device type in hex %T Minor device type in hex %u User ID of owner %U User name of owner %x Time of last access %X Time of last access as seconds since Epoch %y Time of last modification %Y Time of last modification as seconds since Epoch %z Time of last change %Z Time of last change as seconds since Epoch Valid format sequences for file systems: %a Free blocks available to non-superuser %b Total data blocks in file system %c Total file nodes in file system %d Free file nodes in file system %f Free blocks in file system %C Security context in SELinux %i File System ID in hex %l Maximum length of filenames %n File name %s Block size (for faster transfers) %S Fundamental block size (for block counts) %t Type in hex %T Type in human readable form NOTE: your shell may have its own version of stat, which usually supersedes the version described here. Please refer to your shell’s documentation for details about the options it supports. AUTHOR Written by Michael Meskes. REPORTING BUGS Report bugs to <bug-coreutils@gnu.org>. COPYRIGHT Copyright © 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 The full documentation for stat is maintained as a Texinfo manual. If the info and stat programs are properly installed at your site, the command info stat should give you access to the complete manual. stat 5.97 February 2010 STAT(1)
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