文件与目录操作

01.01 ls命令
默认显示当前路径下的所有文件列表,如果要显示其他路径的内容需要跟上一个路径,可以是相对路径也可以是绝对路径.
如果要显示文件的详细信息,需要使用ls的长格式输出-l选项
 # ls -l /dev/
    1 权限 -普通文件,d目录,l链接文件,c字符设备文件,b块设备文件
    2 链接数
    3 属主
    4 属组
    5 大小
    6 修改时间
    7 文件名
会对不同的文件进行加亮显示,蓝色显示的一般表示目录,浅蓝色表示的是链接文件,绿色表示的是可执行文件.
所有以.开头的文件都是隐藏的;如果要将一个文件具有隐藏属性只要将文件名改名为以.开头即可;
ls -a选项可以显示出所有文件,包括隐藏文件;
-a和-l选项是可以组合使用的;
ls -i选项可以显示对应的目录文件的索引节点号inode;
如果两个文件的inode相同,则这两个文件对应的其实是同一个文件;

NAME
       ls - list directory contents
SYNOPSIS
       ls [OPTION]... [FILE]...
DESCRIPTION
       List  information about the FILEs (the current directory by default).  Sort entries alphabetically if none of -cftuvSUX nor --sort is specified.
       -a, --all
              do not ignore entries starting with .
       -h, --human-readable
              with -l, print sizes in human readable format (e.g., 1K 234M 2G)
       -i, --inode
              print the index number of each file
       -I, --ignore=PATTERN
              do not list implied entries matching shell PATTERN
       -l     use a long listing format
       -L, --dereference
       -r, --reverse
              reverse order while sorting
       -R, --recursive
              list subdirectories recursively
       -S     sort by file size
       -t     sort by modification time, newest first
       -1     list one file per line
       --help display this help and exit
       --version
              output version information and exit
   Exit status:
       0      if OK,
       1      if minor problems (e.g., cannot access subdirectory),
       2      if serious trouble (e.g., cannot access command-line argument).

01.02 cd命令
用于切换用户当前目录change directory
cd 后面跟我们要切换的目标路径
在Linux里面有三种方式可以快速切换到用户主目录
cd不加任何参数;cd ~也可以切换到用户主目录;另外cd $HOME也可以快速返回用户主目录;
cd命令的使用频率非常高;

01.03 cp命令copy
可以将一个或多个文件组织到一个目录
 # cp source target
当目录是一个路径的时候表示将文件的名称保留,否则有可能会对拷贝的结果改名;
souce可以是一个文件,也可以是多个文件;当source是多个文件的时候target一定要是路径,否则无法完成复制;
cp默认是不复制目录的,如果要复制目录,需要加-r选项;-r和-R是等价的;
如果复制的目标文件已经存在,使用-i选项可以要求用户确认是否覆盖;
source还可以使用通配符,缩短输入长度,增加灵活性,提高效率;
cp还可以实现ln创建链接文件的功能
cp还可以创建硬链接文件
 # cp -l source hardlink
硬链接文件的inode是相同的,实际对应同一个文件;
cp还可以创建符号链接
 # cp -s source symlink
符号链接和源文件的inode是不同的;

NAME
       cp - copy files and directories
SYNOPSIS
       cp [OPTION]... [-T] SOURCE DEST
       cp [OPTION]... SOURCE... DIRECTORY
       cp [OPTION]... -t DIRECTORY SOURCE...
DESCRIPTION
       Copy SOURCE to DEST, or multiple SOURCE(s) to DIRECTORY.
       -a, --archive
              same as -dR --preserve=all
       -d     same as --no-dereference --preserve=links
       -f, --force
              if an existing destination file cannot be opened, remove it and try again (redundant if the -n option is used)
       -i, --interactive
              prompt before overwrite (overrides a previous -n option)
       -l, --link
              hard link files instead of copying
       -n, --no-clobber
              do not overwrite an existing file (overrides a previous -i option)
       -R, -r, --recursive
              copy directories recursively
       -s, --symbolic-link
              make symbolic links instead of copying
       -t, --target-directory=DIRECTORY
              copy all SOURCE arguments into DIRECTORY
       -u, --update
              copy only when the SOURCE file is newer than the destination file or when the destination file is missing
       -v, --verbose
              explain what is being done
       --help display this help and exit
       --version
              output version information and exit


01.04 mv命令
用来对文件移动或改名
 # mv source target
当source和target都是文件名或者都是文件名时为改名
当target是路径名时表示移动文件,此时source可以是多个文件
NAME
       mv - move (rename) files
SYNOPSIS
       mv [OPTION]... [-T] SOURCE DEST
       mv [OPTION]... SOURCE... DIRECTORY
       mv [OPTION]... -t DIRECTORY SOURCE...
DESCRIPTION
       Rename SOURCE to DEST, or move SOURCE(s) to DIRECTORY.
       -f, --force
              do not prompt before overwriting
       -i, --interactive
              prompt before overwrite
       -n, --no-clobber
              do not overwrite an existing file
       If you specify more than one of -i, -f, -n, only the final one takes effect.
       -t, --target-directory=DIRECTORY
              move all SOURCE arguments into DIRECTORY
       -T, --no-target-directory
              treat DEST as a normal file
       -u, --update
              move only when the SOURCE file is newer than the destination file or when the destination file is missing
       -v, --verbose
              explain what is being done
       --help display this help and exit
       --version
              output version information and exit

01.05 pwd指令
用于显示当前目录的绝对路径
NAME
       pwd - print name of current/working directory
SYNOPSIS
       pwd [OPTION]...
DESCRIPTION
       Print the full filename of the current working directory.
       -L, --logical
              use PWD from environment, even if it contains symlinks
       -P, --physical
              avoid all symlinks
       --help display this help and exit
       --version
              output version information and exit

01.06 rm命令
用于删除文件或目录
 # rm filename
-i选项可以进行删除前确认
-f选项可以强制删除不给出确认信息
-r选项可以递归删除非空目录;-R与-r等效;

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  the  -I or --interactive=once option is given, and there are more than three files or the -r, -R, or --recursive are given, then rm prompts the user for whether to proceed with the entire operation.  If the response is not affirmative,  the  entire  command  is aborted.
       Otherwise, if a file is unwritable, standard input is a terminal, and the -f or --force option is not given, or the -i or --interac‐tive=always option is given, rm prompts the user for whether to remove the file.  If the response is not affirmative,  the  file  is skipped.

OPTIONS
       -f, --force
              ignore nonexistent files, never prompt
       -i     prompt before every removal
       -I     prompt once before removing more than three files, or when removing recursively.  Less intrusive than -i, while still giving protection against most mistakes
       -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.

01.07 mkdir命令
用于创建空目录
 # mkdir dir
使用-p选项可以一次创建多级目录
NAME
       mkdir - make directories
SYNOPSIS
       mkdir [OPTION]... DIRECTORY...
DESCRIPTION
       -m, --mode=MODE
              set file mode (as in chmod), not a=rwx - umask
       -p, --parents
              no error if existing, make parent directories as needed
       -v, --verbose
              print a message for each created directory
       --help display this help and exit
       --version
              output version information and exit

01.08 rmdir命令
用于删除空目录
默认无法删除非空目录
 # rm -rf directory    //可以删除非空目录
-p选项可以删除多级空目录,要求子目录下不能有其他文件存在;
NAME
       rmdir - remove empty directories
SYNOPSIS
       rmdir [OPTION]... DIRECTORY...
DESCRIPTION
       Remove the DIRECTORY(ies), if they are empty.
       -p, --parents
              remove DIRECTORY and its ancestors; e.g., `rmdir -p a/b/c' is similar to `rmdir a/b/c a/b a'
       -v, --verbose
              output a diagnostic for every directory processed
       --help display this help and exit
       --version
              output version information and exit


01.09 chgrp命令
用来改变文件的属组
 # chgrp newgrp file
使用-R选项可以改变目录及其子文件的属组
 # chgrp -R newgrp dir
NAME
       chgrp - change group ownership
SYNOPSIS
       chgrp [OPTION]... GROUP FILE...
       chgrp [OPTION]... --reference=RFILE FILE...
DESCRIPTION
       Change the group of each FILE to GROUP.  With --reference, change the group of each FILE to that of RFILE.
       -c, --changes
              like verbose but report only when a change is made
       --reference=RFILE
              use RFILE's group rather than specifying a GROUP value
       -R, --recursive
              operate on files and directories recursively
       -v, --verbose
              output a diagnostic for every file processed
       The following options modify how a hierarchy is traversed when the -R option is also specified.  If more than one is specified, only the final one takes effect.
       -H     if a command line argument is a symbolic link to a directory, traverse it
       -L     traverse every symbolic link to a directory encountered
       -P     do not traverse any symbolic links (default)
       --help display this help and exit
       --version
              output version information and exit
EXAMPLES
       # chgrp staff /u
              Change the group of /u to "staff".
       # chgrp -hR staff /u


01.10 chmod命令
用来改变文件的权限
u,user;g,group;o,others;a,all;
 # chmod u=rwx,g=rw,o=rw file
 # chmod u+x file
 # chmod a+x file
 # chmod 644 file
NAME
       chmod - change file mode bits
SYNOPSIS
       chmod [OPTION]... MODE[,MODE]... FILE...
       chmod [OPTION]... OCTAL-MODE FILE...
       chmod [OPTION]... --reference=RFILE FILE...
OPTIONS
       Change the mode of each FILE to MODE.
       -c, --changes
              like verbose but report only when a change is made
       -v, --verbose
              output a diagnostic for every file processed
       --reference=RFILE
              use RFILE's mode instead of MODE values
       -R, --recursive
              change files and directories recursively
       --help display this help and exit
       --version
              output version information and exit


01.11 chown命令
改变文件的属主和属组
 # chown owner file
 # chown owner:grp file
 # chown -R owner file
NAME
       chown - change file owner and group
SYNOPSIS
       chown [OPTION]... [OWNER][:[GROUP]] FILE...
       chown [OPTION]... --reference=RFILE FILE...
OPTIONS
       Change  the  owner  and/or  group  of each FILE to OWNER and/or GROUP.  With --reference, change the owner and group of each FILE to those of RFILE.
       -c, --changes
              like verbose but report only when a change is made
       --reference=RFILE
              use RFILE's owner and group rather than specifying OWNER:GROUP values
       -R, --recursive
              operate on files and directories recursively
       -v, --verbose
              output a diagnostic for every file processed
       The following options modify how a hierarchy is traversed when the -R option is also specified.  If more than one is specified, only the final one takes effect.
       -H     if a command line argument is a symbolic link to a directory, traverse it
       -L     traverse every symbolic link to a directory encountered
       -P     do not traverse any symbolic links (default)
       --help display this help and exit
       --version
              output version information and exit
EXAMPLES
       # chown root /u
               Change the owner of /u to "root".
       # chown root:staff /u
               Likewise, but also change its group to "staff".
       # chown -hR root /u
               Change the owner of /u and subfiles to "root".


01.12 find命令
可以查找文件
在linux中使用频率比较高
 # find / -name passwd    /* 从/开始查找name为passwd的文件,并把结果输出 */
还可以对查找的结果进行操作
 # find ./ -name day01.txt -exec ls -l {} \;
/* 表示对find查找的name为day01.txt的文件调用ls -l命令,{}代表find的结果 */
 # find ./ -depth -type d -empty //查找空文件夹
 # find ./ -depth -type f -empty //查找空文件
 # find ./ -name test.txt    //查找文件名为test.txt的文件
 # find ./ -name "*.txt"    //查找后缀为txt的文件
 # find ./ -name "*.txt" -perm 644    //查找具有特定权限且有且定扩展名的文件
 # find ./ -perm 664        //查找具有特定权限的文件
 # find ./ -name "file.*"    //查找不知道扩展名只使用文件名来查找文件
 # find ./ -mtime 2    //查找2+1天(*24hour)内修改过的文件
 # find -atime 0    //查找24小时内存取过的文件
 # find ./ -user root    //查找所有者的文件
 # find ./ -name test.txt | xargs rm //查找并删除查找到的文件
 # find ./ -name "out" -prune -o -iname "bin" 查找除out目录外的bin文件且部分大小写

NAME
       find - search for files in a directory hierarchy
SYNOPSIS
       find [-H] [-L] [-P] [-D debugopts] [-Olevel] [path...] [expression]

EXPRESSIONS
       The  expression  is  made  up  of  options (which affect overall operation rather than the processing of a specific file, and always return true), tests (which return a true or false value), and actions (which have side effects and return a true  or  false  value), all separated by operators.  -and is assumed where the operator is omitted.

       If the expression contains no actions other than -prune, -print is performed on all files for which the expression is true.


  OPTIONS
       All  options always return true.  Except for -daystart, -follow and -regextype, the options affect all tests, including tests specified before the option.  This is because the options are processed when the command line is parsed, while the tests  do not  do  anything  until  files  are  examined.  The -daystart, -follow and -regextype options are different in this respect, and have an effect only on tests which appear later in the command line.  Therefore, for clarity, it is best to place them  at  the  beginning  of  the
       expression.  A warning is issued if you don't do this.

       -d     A synonym for -depth, for compatibility with FreeBSD, NetBSD, MacOS X and OpenBSD.
       -daystart
              Measure  times  (for  -amin,  -atime, -cmin, -ctime, -mmin, and -mtime) from the beginning of today rather than from 24 hours ago.  This option only affects tests which appear later on the command line.
       -depth Process each directory's contents before the directory itself.  The -delete action also implies -depth.

       -follow
              Deprecated; use the -L option instead.  Dereference symbolic links.  Implies -noleaf.  The -follow option affects only  those tests  which appear after it on the command line.  Unless the -H or -L option has been specified, the position of the -follow option changes the behaviour of the -newer predicate; any files listed as the argument of -newer will be dereferenced if they are  symbolic  links.   The same consideration applies to -newerXY, -anewer and -cnewer.  Similarly, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself.  Using  -follow  causes the -lname and -ilname predicates always to return false.

       -help, --help
              Print a summary of the command-line usage of find and exit.

       -ignore_readdir_race
              Normally,  find  will  emit  an  error  message  when it fails to stat a file.  If you give this option and a file is deleted between the time find reads the name of the file from the directory and the time it tries to stat the file, no error  message will  be  issued.     This also applies to files or directories whose names are given on the command line.  This option takes effect at the time the command line is read, which means that you cannot search one part of the filesystem with  this  option on  and  part  of it with this option off (if you need to do that, you will need to issue two find commands instead, one with the option and one without it).

       -maxdepth levels
              Descend at most levels (a non-negative integer) levels of directories below the command line arguments.  -maxdepth 0 means only apply the tests and actions to the command line arguments.

       -mindepth levels
              Do not apply any tests or actions at levels less than levels (a non-negative integer).  -mindepth 1 means process  all  files except the command line arguments.

       -mount Don't  descend  directories on other filesystems.  An alternate name for -xdev, for compatibility with some other versions of find.

       -noignore_readdir_race
              Turns off the effect of -ignore_readdir_race.

       -noleaf
              Do not optimize by assuming that directories contain 2 fewer subdirectories than their  hard  link  count.   This  option  is needed when searching filesystems that do not follow the Unix directory-link convention, such as CD-ROM or MS-DOS filesystems or AFS volume mount points.  Each directory on a normal Unix filesystem has at least 2 hard  links:  its  name  and  its  `.' entry.  Additionally, its subdirectories (if any) each have a `..'  entry linked to that directory.  When find is examining a directory, after it has statted 2 fewer subdirectories than the directory's link count, it knows that the rest of the entries in  the  directory  are  non-directories (`leaf' files in the directory tree).  If only the files' names need to be examined, there is no need to stat them; this gives a significant increase in search speed.

       -regextype type
              Changes the regular expression syntax understood by -regex and -iregex tests which occur later on  the  command  line.   Currently-implemented types are emacs (this is the default), posix-awk, posix-basic, posix-egrep and posix-extended.

       -version, --version
              Print the find version number and exit.

       -warn, -nowarn
              Turn  warning messages on or off.  These warnings apply only to the command line usage, not to any conditions that find might encounter when it searches directories.  The default behaviour corresponds to -warn if  standard  input  is  a  tty,  and  to -nowarn otherwise.

       -xdev  Don't descend directories on other filesystems.

  TESTS
       Some  tests,  for example -newerXY and -samefile, allow comparison between the file currently being examined and some reference file specified on the command line.  When these tests are used, the interpretation of the reference file is determined by the options -H, -L  and  -P  and any previous -follow, but the reference file is only examined once, at the time the command line is parsed.  If the reference file cannot be examined (for example, the stat(2) system call fails for it), an error message is issued,  and  find  exits with a nonzero status.

       Numeric arguments can be specified as
       +n     for greater than n,
       -n     for less than n,
       n      for exactly n.

       -amin n
              File was last accessed n minutes ago.

       -anewer file
              File  was  last accessed more recently than file was modified.  If file is a symbolic link and the -H option or the -L option is in effect, the access time of the file it points to is always used.

       -atime n
              File was last accessed n*24 hours ago.  When find figures out how many 24-hour periods ago the file was  last  accessed,  any fractional part is ignored, so to match -atime +1, a file has to have been accessed at least two days ago.

       -cmin n
              File's status was last changed n minutes ago.

       -cnewer file
              File's  status was last changed more recently than file was modified.  If file is a symbolic link and the -H option or the -L
              option is in effect, the status-change time of the file it points to is always used.

       -ctime n
              File's status was last changed n*24 hours ago.  See the comments for -atime to understand how rounding affects the  interpretation of file status change times.

       -empty File is empty and is either a regular file or a directory.

       -executable
              Matches  files  which are executable and directories which are searchable (in a file name resolution sense).  This takes into account access control lists and other permissions artefacts which the -perm test  ignores.   This  test  makes  use  of  the access(2)  system  call,  and  so  can  be fooled by NFS servers which do UID mapping (or root-squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server.  Because this  test  is  based  only on the result of the access(2) system call, there is no guarantee that a file for which this test succeeds can actually be executed.

       -false Always false.

       -fstype type
              File is on a filesystem of type type.  The valid filesystem types vary among different versions of Unix; an  incomplete  list of  filesystem  types that are accepted on some version of Unix or another is: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K.  You can use -printf with the %F directive to see the types of your filesystems.

       -gid n File's numeric group ID is n.

       -group gname
              File belongs to group gname (numeric group ID allowed).

       -ilname pattern
              Like -lname, but the match is case insensitive.  If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken.

       -iname pattern
              Like  -name, but the match is case insensitive.  For example, the patterns `fo*' and `F??' match the file names `Foo', `FOO', `foo', `fOo', etc.   In these patterns, unlike filename expansion by the shell, an initial '.' can be matched by  `*'.   That is, find -name *bar will match the file `.foobar'.   Please note that you should quote patterns as a matter of course, otherwise the shell will expand any wildcard characters in them.

       -inum n
              File has inode number n.  It is normally easier to use the -samefile test instead.

       -ipath pattern
              Behaves in the same way as -iwholename.  This option is deprecated, so please do not use it.

       -iregex pattern
              Like -regex, but the match is case insensitive.

       -iwholename pattern
              Like -wholename, but the match is case insensitive.

       -links n
              File has n links.

       -lname pattern
              File is a symbolic link whose contents match shell pattern pattern.  The metacharacters do not treat `/'  or  `.'  specially.  If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken.

       -mmin n
              File's data was last modified n minutes ago.

       -mtime n
              File's data was last modified n*24 hours ago.  See the comments for -atime to understand how rounding affects the interpretation of file modification times.

       -name pattern
              Base of file name (the path with the leading directories removed) matches shell pattern pattern.   The  metacharacters  (`*', `?',  and `[]') match a `.' at the start of the base name (this is a change in findutils-4.2.2; see section STANDARDS CONFORMANCE below).  To ignore a directory and the files under it, use -prune; see an example in the description of -path.   Braces are  not recognised as being special, despite the fact that some shells including Bash imbue braces with a special meaning in shell patterns.  The filename matching is performed with the use of  the  fnmatch(3)  library  function. Don't  forget  to enclose the pattern in quotes in order to protect it from expansion by the shell.

       -newer file
              File  was  modified more recently than file.  If file is a symbolic link and the -H option or the -L option is in effect, the modification time of the file it points to is always used.

       -newerXY reference
              Compares the timestamp of the current file with reference.  The reference argument is normally the name of a file (and one of its timestamps is used for the comparison) but it may also be a string describing an absolute time.  X and Y are placeholders for other letters, and these letters select which time belonging to how reference is used for the comparison.

              a   The access time of the file reference
              B   The birth time of the file reference
              c   The inode status change time of reference
              m   The modification time of the file reference
              t   reference is interpreted directly as a time

              Some combinations are invalid; for example, it is invalid for X to be t.  Some combinations are not implemented on  all  systems;  for  example  B is not supported on all systems.  If an invalid or unsupported combination of XY is specified, a fatal error results.  Time specifications are interpreted as for the argument to the -d option of GNU date.  If you try to use  the birth  time  of  a  reference file, and the birth time cannot be determined, a fatal error message results.  If you specify a test which refers to the birth time of files being examined, this test will fail for  any  files  where  the  birth  time  is unknown.

       -nogroup
              No group corresponds to file's numeric group ID.

       -nouser
              No user corresponds to file's numeric user ID.

       -path pattern
              File name matches shell pattern pattern.  The metacharacters do not treat `/' or `.' specially; so, for example, find . -path "./sr*sc" will print an entry for a directory called `./src/misc' (if one exists).  To ignore a whole directory tree, use -prune rather than checking every file in the tree.  For example, to skip the directory `src/emacs' and all files and directories under it, and print the names of the other files found, do something like this:
                        find . -path ./src/emacs -prune -o -print
              Note  that  the pattern match test applies to the whole file name, starting from one of the start points named on the command line.  It would only make sense to use an absolute path name here if the relevant start point is also an absolute path.  This means that this command will never match anything:
                        find bar -path /foo/bar/myfile -print
              The predicate -path is also supported by HP-UX find and will be in a forthcoming version of the POSIX standard.

       -perm mode
              File's  permission bits are exactly mode (octal or symbolic).  Since an exact match is required, if you want to use this form for symbolic modes, you may have to specify a rather complex mode string.  For example -perm g=w will only match files  which have  mode 0020 (that is, ones for which group write permission is the only permission set).  It is more likely that you will want to use the `/' or `-' forms, for example -perm -g=w, which matches any file with group write permission.  See the  EXAMPLES section for some illustrative examples.

       -perm -mode
              All  of the permission bits mode are set for the file.  Symbolic modes are accepted in this form, and this is usually the way in which would want to use them.  You must specify `u', `g' or `o' if you use a symbolic mode.   See the EXAMPLES section for some illustrative examples.

       -perm /mode
              Any  of  the permission bits mode are set for the file.  Symbolic modes are accepted in this form.  You must specify `u', `g' or `o' if you use a symbolic mode.  See the EXAMPLES section for some illustrative examples.  If no permission bits  in  mode are set, this test matches any file (the idea here is to be consistent with the behaviour of -perm -000).

       -perm +mode
              Deprecated,  old way of searching for files with any of the permission bits in mode set.  You should use -perm /mode instead.  Trying to use the `+' syntax with symbolic modes will yield surprising results.  For example, `+u+x' is a valid symbolic mode (equivalent  to  +u,+x, i.e. 0111) and will therefore not be evaluated as -perm +mode but instead as the exact mode specifier -perm mode and so it matches files with exact permissions 0111 instead of files with any execute bit set.  If you found  this paragraph  confusing,  you're  not alone - just use -perm /mode.  This form of the -perm test is deprecated because the POSIX specification requires the interpretation of a leading `+' as being part of a symbolic mode, and so we switched to using  `/' instead.

       -readable
              Matches  files  which  are  readable.  This takes into account access control lists and other permissions artefacts which the -perm test ignores.  This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID  mapping  (or  root-squashing),  since  many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server.

       -regex pattern
              File name matches regular expression pattern.  This is a match on the whole path, not a search.  For example, to match a file named  `./fubar3',  you can use the regular expression `.*bar.' or `.*b.*3', but not `f.*r3'.  The regular expressions understood by find are by default Emacs Regular Expressions, but this can be changed with the -regextype option.

       -samefile name
              File refers to the same inode as name.   When -L is in effect, this can include symbolic links.

       -size n[cwbkMG]
              File uses n units of space.  The following suffixes can be used:
              `b'    for 512-byte blocks (this is the default if no suffix is used)
              `c'    for bytes
              `w'    for two-byte words
              `k'    for Kilobytes (units of 1024 bytes)
              `M'    for Megabytes (units of 1048576 bytes)
              `G'    for Gigabytes (units of 1073741824 bytes)

              The size does not count indirect blocks, but it does count blocks in sparse files that are not actually allocated.   Bear  in mind  that  the  `%k'  and  `%b' format specifiers of -printf handle sparse files differently.  The `b' suffix always denotes 512-byte blocks and never 1 Kilobyte blocks, which is different to the behaviour of -ls.

       -true  Always true.

       -type c
              File is of type c:
              b      block (buffered) special
              c      character (unbuffered) special
              d      directory
              p      named pipe (FIFO)
              f      regular file
              l      symbolic link; this is never true if the -L option or the -follow option is in effect, unless the symbolic link is broken.  If you want to search for symbolic links when -L is in effect, use -xtype.
              s      socket
              D      door (Solaris)

       -uid n File's numeric user ID is n.

       -used n
              File was last accessed n days after its status was last changed.

       -user uname
              File is owned by user uname (numeric user ID allowed).

       -wholename pattern
              See -path.    This alternative is less portable than -path.

       -writable
              Matches  files  which  are  writable.  This takes into account access control lists and other permissions artefacts which the -perm test ignores.  This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID  mapping  (or  root-squashing),  since  many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server.

       -xtype c
              The same as -type unless the file is a symbolic link.  For symbolic links: if the -H or -P option was specified, true if  the file  is  a link to a file of type c; if the -L option has been given, true if c is `l'.  In other words, for symbolic links, -xtype checks the type of the file that -type does not check.  

  ACTIONS
       -delete
              Delete files; true if removal succeeded.  If the removal failed, an error message is issued.  If -delete fails,  find's  exit status will be nonzero (when it eventually exits).  Use of -delete automatically turns on the -depth option.

              Warnings:  Don't forget that the find command line is evaluated as an expression, so putting -delete first will make find try to delete everything below the starting points you specified.  When testing a find command line that you later intend to  use with  -delete,  you  should explicitly specify -depth in order to avoid later surprises.  Because -delete implies -depth, you cannot usefully use -prune and -delete together.

       -exec command ;
              Execute command; true if 0 status is returned.  All following arguments to find are taken to  be  arguments  to  the  command until  an  argument  consisting  of `;' is encountered.  The string `{}' is replaced by the current file name being processed everywhere it occurs in the arguments to the command, not just in arguments where it is alone, as in some versions  of  find.
              Both of these constructions might need to be escaped (with a `\') or quoted to protect them from expansion by the shell.  See the EXAMPLES section for examples of the use of the -exec option.  The specified command is run once for each  matched  file.
              The  command  is  executed  in the starting directory.   There are unavoidable security problems surrounding use of the -exec action; you should use the -execdir option instead.

       -exec command {} +
              This variant of the -exec action runs the specified command on the selected files, but the command line is built by appending each  selected  file  name  at  the  end; the total number of invocations of the command will be much less than the number of matched files.  The command line is built in much the same way that xargs builds its command lines.   Only  one  instance  of `{}' is allowed within the command.  The command is executed in the starting directory.

       -execdir command ;

       -execdir command {} +
              Like  -exec,  but  the  specified command is run from the subdirectory containing the matched file, which is not normally the directory in which you started find.  This a much more secure method for invoking commands, as it avoids race conditions during  resolution  of  the paths to the matched files.  As with the -exec action, the `+' form of -execdir will build a command line to process more than one matched file, but any given invocation of command will only list files that exist in  the  same subdirectory.   If  you  use this option, you must ensure that your $PATH environment variable does not reference `.'; otherwise, an attacker can run any commands they like by leaving an appropriately-named file in a directory in which you will  run -execdir.  The same applies to having entries in $PATH which are empty or which are not absolute directory names.

       -fls file
              True;  like  -ls  but write to file like -fprint.  The output file is always created, even if the predicate is never matched.
              See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled.

       -fprint file
              True; print the full file name into file file.  If file does not exist when find is run, it is created; if it does exist,  it is  truncated.   The  file names ``/dev/stdout'' and ``/dev/stderr'' are handled specially; they refer to the standard output and standard error output, respectively.  The output file is always created, even if the predicate is never matched.  See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled.

       -fprint0 file
              True;  like  -print0  but  write  to  file  like  -fprint.  The output file is always created, even if the predicate is never matched.  See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled.

       -fprintf file format
              True; like -printf but write to file like -fprint.  The output file is  always  created,  even  if  the  predicate  is  never matched.  See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled.

       -ls    True;  list  current  file  in ls -dils format on standard output.  The block counts are of 1K blocks, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used.  See the UNUSUAL FILENAMES section  for  information about how unusual characters in filenames are handled.

       -ok command ;
              Like  -exec  but  ask  the user first.  If the user agrees, run the command.  Otherwise just return false.  If the command is run, its standard input is redirected from /dev/null.

              The response to the prompt is matched against a pair of regular expressions to determine if it is an affirmative or  negative response.   This regular expression is obtained from the system if the `POSIXLY_CORRECT' environment variable is set, or otherwise from find's message translations.  If the system has no suitable definition, find's own definition will be used.    In either  case,  the  interpretation  of the regular expression itself will be affected by the environment variables 'LC_CTYPE' (character classes) and 'LC_COLLATE' (character ranges and equivalence classes).

       -okdir command ;
              Like -execdir but ask the user first in the same way as for -ok.  If the user does not agree, just return false.  If the command is run, its standard input is redirected from /dev/null.

       -print True;  print  the  full  file name on the standard output, followed by a newline.   If you are piping the output of find into another program and there is the faintest possibility that the files which you are searching for  might  contain  a  newline, then  you should seriously consider using the -print0 option instead of -print.  See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled.

       -print0
              True; print the full file name on the standard output, followed by a null character (instead of the  newline  character  that -print uses).  This allows file names that contain newlines or other types of white space to be correctly interpreted by programs that process the find output.  This option corresponds to the -0 option of xargs.

       -printf format
              True; print format on the standard output, interpreting `\' escapes and `%' directives.  Field widths and precisions  can  be specified  as  with  the `printf' C function.  Please note that many of the fields are printed as %s rather than %d, and this may mean that flags don't work as you might expect.  This also means that the `-' flag does work  (it  forces  fields  to  be left-aligned).  Unlike -print, -printf does not add a newline at the end of the string.  The escapes and directives are:
              \a     Alarm bell.
              \b     Backspace.
              \c     Stop printing from this format immediately and flush the output.
              \f     Form feed.
              \n     Newline.
              \r     Carriage return.
              \t     Horizontal tab.
              \v     Vertical tab.
              \0     ASCII NUL.
              \\     A literal backslash (`\').
              \NNN   The character whose ASCII code is NNN (octal).
              A `\' character followed by any other character is treated as an ordinary character, so they both are printed.
              %%     A literal percent sign.
              %a     File's last access time in the format returned by the C `ctime' function.
              %Ak    File's  last  access  time in the format specified by k, which is either `@' or a directive for the C `strftime' function.  The possible values for k are listed below; some of them might not be available on all systems, due to  differences in `strftime' between systems.
              @      seconds since Jan. 1, 1970, 00:00 GMT, with fractional part.
              Time fields:
                     H      hour (00..23)
                     I      hour (01..12)
                     k      hour ( 0..23)
                     l      hour ( 1..12)
                     M      minute (00..59)
                     p      locale's AM or PM
                     r      time, 12-hour (hh:mm:ss [AP]M)
                     S      Second (00.00 .. 61.00).  There is a fractional part.
                     T      time, 24-hour (hh:mm:ss)
                     +      Date  and  time,  separated by `+', for example `2004-04-28+22:22:05.0'.  This is a GNU extension.  The time is given in the current timezone (which may be affected by setting the  TZ  environment  variable).   The  seconds field includes a fractional part.
                     X      locale's time representation (H:M:S)
                     Z      time zone (e.g., EDT), or nothing if no time zone is determinable

               Date fields:
                     a      locale's abbreviated weekday name (Sun..Sat)
                     A      locale's full weekday name, variable length (Sunday..Saturday)
                     b      locale's abbreviated month name (Jan..Dec)
                     B      locale's full month name, variable length (January..December)
                     c      locale's  date  and time (Sat Nov 04 12:02:33 EST 1989).  The format is the same as for ctime(3) and so to preserve compatibility with that format, there is no fractional part in the seconds field.
                     d      day of month (01..31)
                     D      date (mm/dd/yy)
                     h      same as b
                     j      day of year (001..366)
                     m      month (01..12)
                     U      week number of year with Sunday as first day of week (00..53)
                     w      day of week (0..6)
                     W      week number of year with Monday as first day of week (00..53)
                     x      locale's date representation (mm/dd/yy)
                     y      last two digits of year (00..99)
                     Y      year (1970...)

              %b     The amount of disk space used for this file in 512-byte blocks. Since disk space is  allocated  in  multiples  of  the filesystem block size this is usually greater than %s/512, but it can also be smaller if the file is a sparse file.
              %c     File's last status change time in the format returned by the C `ctime' function.
              %Ck    File's last status change time in the format specified by k, which is the same as for %A.
              %d     File's depth in the directory tree; 0 means the file is a command line argument.
              %D     The device number on which the file exists (the st_dev field of struct stat), in decimal.
              %f     File's name with any leading directories removed (only the last element).
              %F     Type of the filesystem the file is on; this value can be used for -fstype.
              %g     File's group name, or numeric group ID if the group has no name.
              %G     File's numeric group ID.
              %h     Leading  directories  of file's name (all but the last element).  If the file name contains no slashes (since it is in the current directory) the %h specifier expands to ".".
              %H     Command line argument under which file was found.
              %i     File's inode number (in decimal).
              %k     The amount of disk space used for this file in 1K blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/1024, but it can also be smaller if the file is a sparse file.
              %l     Object of symbolic link (empty string if file is not a symbolic link).
              %m     File's  permission  bits  (in octal).  This option uses the `traditional' numbers which most Unix implementations use, but if your particular implementation uses an unusual ordering of octal permissions bits, you will  see  a  difference between  the  actual value of the file's mode and the output of %m.   Normally you will want to have a leading zero on this number, and to do this, you should use the # flag (as in, for example, `%#m').
              %M     File's permissions (in symbolic form, as for ls).  This directive is supported in findutils 4.2.5 and later.
              %n     Number of hard links to file.
              %p     File's name.
              %P     File's name with the name of the command line argument under which it was found removed.
              %s     File's size in bytes.
              %S     File's sparseness.  This is calculated as (BLOCKSIZE*st_blocks / st_size).  The exact value you will get for an  ordinary file of a certain length is system-dependent.  However, normally sparse files will have values less than 1.0, and files which use indirect blocks may have a value which is greater than 1.0.   The value used for BLOCKSIZE is  systemdependent,  but  is  usually  512 bytes.   If the file size is zero, the value printed is undefined.  On systems which lack support for st_blocks, a file's sparseness is assumed to be 1.0.
              %t     File's last modification time in the format returned by the C `ctime' function.
              %Tk    File's last modification time in the format specified by k, which is the same as for %A.
              %u     File's user name, or numeric user ID if the user has no name.
              %U     File's numeric user ID.
              %y     File's type (like in ls -l), U=unknown type (shouldn't happen)
              %Y     File's type (like %y), plus follow symlinks: L=loop, N=nonexistent
              A `%' character followed by any other character is discarded, but the other character is printed (don't rely on this, as further format characters may be introduced).  A `%' at the end of the format argument causes undefined behaviour since there is no following character.  In some locales, it may hide your door keys, while in others it may remove the final page  from  the novel you are reading.

              The %m and %d directives support the # , 0 and + flags, but the other directives do not, even if they print numbers.  Numeric directives that do not support these flags include G, U, b, D, k and n.  The `-' format flag is  supported  and  changes  the alignment of a field from right-justified (which is the default) to left-justified.

              See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled.

       -prune True;  if  the  file  is  a directory, do not descend into it. If -depth is given, false; no effect.  Because -delete implies -depth, you cannot usefully use -prune and -delete together.

       -quit  Exit immediately.  No child processes will be left running, but no more paths specified on the  command  line  will  be  processed.   For example, find /tmp/foo /tmp/bar -print -quit will print only /tmp/foo.  Any command lines which have been built up with -execdir ... {} + will be invoked before find exits.   The exit status may or may not be zero, depending  on  whether an error has already occurred.

UNUSUAL FILENAMES
       Many  of  the  actions  of find result in the printing of data which is under the control of other users.  This includes file names, sizes, modification times and so forth.  File names are a potential problem since they can contain any  character  except  `\0'  and `/'.   Unusual  characters  in file names can do unexpected and often undesirable things to your terminal (for example, changing the settings of your function keys on some terminals).  Unusual characters are handled differently  by  various  actions,  as  described below.

       -print0, -fprint0
              Always print the exact filename, unchanged, even if the output is going to a terminal.

       -ls, -fls
              Unusual  characters are always escaped.  White space, backslash, and double quote characters are printed using C-style escaping (for example `\f', `\"').  Other unusual characters are printed using an octal escape.  Other printable  characters  (for -ls and -fls these are the characters between octal 041 and 0176) are printed as-is.

       -printf, -fprintf
              If  the  output is not going to a terminal, it is printed as-is.  Otherwise, the result depends on which directive is in use.
              The directives %D, %F, %g, %G, %H, %Y, and %y expand to values which are not under control  of  files'  owners,  and  so  are printed  as-is.  The directives %a, %b, %c, %d, %i, %k, %m, %M, %n, %s, %t, %u and %U have values which are under the control of files' owners but which cannot be used to send arbitrary data to the terminal, and so these are printed as-is.  The directives %f, %h, %l, %p and %P are quoted.  This quoting is performed in the same way as for GNU ls.  This is not the same quoting mechanism as the one used for -ls and -fls.  If you are able to decide what format to use for the output of find then  it is normally better to use `\0' as a terminator than to use newline, as file names can contain white space and newline characters.  The setting of the `LC_CTYPE' environment variable is used to determine which characters need to be quoted.

       -print, -fprint
              Quoting is handled in the same way as for -printf and -fprintf.  If you are using find in a script or in  a  situation  where the matched files might have arbitrary names, you should consider using -print0 instead of -print.

       The -ok and -okdir actions print the current filename as-is.  This may change in a future release.

OPERATORS
       Listed in order of decreasing precedence:

       ( expr )
              Force precedence.  Since parentheses are special to the shell, you will normally need to quote them.  Many of the examples in this manual page use backslashes for this purpose: `\(...\)' instead of `(...)'.

       ! expr True if expr is false.  This character will also usually need protection from interpretation by the shell.

       -not expr
              Same as ! expr, but not POSIX compliant.

       expr1 expr2
              Two expressions in a row are taken to be joined with an implied "and"; expr2 is not evaluated if expr1 is false.

       expr1 -a expr2
              Same as expr1 expr2.

       expr1 -and expr2
              Same as expr1 expr2, but not POSIX compliant.

       expr1 -o expr2
              Or; expr2 is not evaluated if expr1 is true.

       expr1 -or expr2
              Same as expr1 -o expr2, but not POSIX compliant.

       expr1 , expr2
              List; both expr1 and expr2 are always evaluated.  The value of expr1 is discarded; the value of the  list  is  the  value  of expr2.  The  comma  operator  can be useful for searching for several different types of thing, but traversing the filesystem hierarchy only once.  The -fprintf action can be used to list the various matched items into several different output files.


STANDARDS CONFORMANCE
       For closest compliance to the POSIX standard, you should set the POSIXLY_CORRECT environment variable.  The  following  options  are
       specified in the POSIX standard (IEEE Std 1003.1, 2003 Edition):
       -H     This option is supported.
       -L     This option is supported.
       -name  This option is supported, but POSIX conformance depends on the POSIX conformance of the system's fnmatch(3) library function.
              As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) will match a leading `.', because IEEE PASC interpretation 126 requires this.   This is a change from previous versions of findutils.

       -type  Supported.    POSIX  specifies  `b', `c', `d', `l', `p', `f' and `s'.  GNU find also supports `D', representing a Door, where the OS provides these.

       -ok    Supported.  Interpretation of the response is according to the "yes" and "no" patterns selected by setting the  `LC_MESSAGES' environment  variable.   When the `POSIXLY_CORRECT' environment variable is set, these patterns are taken system's definition of a positive (yes) or negative (no) response. See the system's documentation for nl_langinfo(3), in particular  YESEXPR  and NOEXPR.    When `POSIXLY_CORRECT' is not set, the patterns are instead taken from find's own message catalogue.

       -newer Supported.   If  the file specified is a symbolic link, it is always dereferenced.  This is a change from previous behaviour, which used to take the relevant time from the symbolic link; see the HISTORY section below.

       -perm  Supported.  If the POSIXLY_CORRECT environment variable is not set, some mode arguments (for  example  +a+x)  which  are  not valid in POSIX are supported for backward-compatibility.

       Other predicates
              The  predicates -atime, -ctime, -depth, -group, -links, -mtime, -nogroup, -nouser, -print, -prune, -size, -user and -xdev are all supported.

       The POSIX standard specifies parentheses `(', `)', negation `!' and the `and' and `or' operators ( -a, -o).


EXAMPLES
    # find /tmp -name core -type f -print | xargs /bin/rm -f
       Find files named core in or below the directory /tmp and delete them.  Note that this will work incorrectly if there are  any  filenames containing newlines, single or double quotes, or spaces.

    # find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f
       Find  files  named  core  in  or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing single or double quotes, spaces or newlines are correctly handled.  The -name test comes before the -type  test  in order to avoid having to call stat(2) on every file.

    # find . -type f -exec file '{}' \;
       Runs  `file'  on every file in or below the current directory.  Notice that the braces are enclosed in single quote marks to protect them from interpretation as shell script punctuation.  The semicolon is similarly protected by the use of a backslash, though single quotes could have been used in that case also.

    # find / \
       \( -perm -4000 -fprintf /root/suid.txt %#m %u %p\n \) , \
       \( -size +100M -fprintf /root/big.txt %-10s %p\n \)

       Traverse the filesystem just once, listing setuid files and directories into /root/suid.txt and large files into /root/big.txt.

    # find $HOME -mtime 0

       Search for files in your home directory which have been modified in the last twenty-four hours.  This command works this way because the time since each file was last modified is divided by 24 hours and any remainder is discarded.  That means that to  match  -mtime 0, a file will have to have a modification in the past which is less than 24 hours ago.

    # find /sbin /usr/sbin -executable \! -readable -print
       Search for files which are executable but not readable.

    # find . -perm 664
       Search  for  files which have read and write permission for their owner, and group, but which other users can read but not write to.
       Files which meet these criteria but have other permissions bits set (for example if someone  can  execute  the  file)  will  not  be matched.

    # find . -perm -664
       Search  for  files which have read and write permission for their owner and group, and which other users can read, without regard to the presence of any extra permission bits (for example the executable bit).  This will match a file which has mode 0777,  for  example.

    # find . -perm /222
       Search for files which are writable by somebody (their owner, or their group, or anybody else).

    # find . -perm /220
    # find . -perm /u+w,g+w
    # find . -perm /u=w,g=w
       All  three  of these commands do the same thing, but the first one uses the octal representation of the file mode, and the other two use the symbolic form.  These commands all search for files which are writable by either their owner  or  their  group.   The  files don't have to be writable by both the owner and group to be matched; either will do.


    # find . -perm -220
    # find . -perm -g+w,u+w
       Both these commands do the same thing; search for files which are writable by both their owner and their group.

    # find . -perm -444 -perm /222 ! -perm /111
    # find . -perm -a+r -perm /a+w ! -perm /a+x
       These  two  commands  both search for files that are readable for everybody ( -perm -444 or -perm -a+r), have at least one write bit set ( -perm /222 or -perm /a+w) but are not executable for anybody ( ! -perm /111 and ! -perm /a+x respectively).

    # cd /source-dir
    # find . -name .snapshot -prune -o \( \! -name *~ -print0 \)|
    # cpio -pmd0 /dest-dir
       This command copies the contents of /source-dir to /dest-dir, but omits files and  directories  named  .snapshot  (and  anything  in them).   It also omits files or directories whose name ends in ~, but not their contents.  The construct -prune -o \( ... -print0 \) is quite common.  The idea here is that the expression before -prune matches things which are to be  pruned.   However,  the  -prune action  itself  returns  true,  so  the  following -o ensures that the right hand side is evaluated only for those directories which didn't get pruned (the contents of the pruned directories are not even visited, so their contents are irrelevant).   The  expression on  the  right  hand  side of the -o is in parentheses only for clarity.  It emphasises that the -print0 action takes place only for things that didn't have -prune applied to them.  Because the default `and' condition between tests binds more tightly than -o,  this is the default anyway, but the parentheses help to show what is going on.

    # find repo/ -exec test -d {}/.svn -o -d {}/.git -o -d {}/CVS ; \
    # -print -prune
       Given  the  following directory of projects and their associated SCM administrative directories, perform an efficient search for the
       projects' roots:
       repo/project1/CVS
       repo/gnu/project2/.svn
       repo/gnu/project3/.svn
       repo/gnu/project3/src/.svn
       repo/project4/.git
       In this example, -prune prevents unnecessary descent into directories that have already been  discovered  (for  example  we  do  not search project3/src because we already found project3/.svn), but ensures sibling directories (project2 and project3) are found.


01.13 ln命令
用来为文件创建链接,硬链接(链接)或符号链接(软链接);
 # ln src linkname
 # ln -s dir linkname
硬链接不能跨越分区或文件系统,符号链接则没有此限制;
硬链接也不能针对目录来创建,符号连接则无次限制;
软链接文件存储的是源文件名

01.14 whereis命令
用来定位指令的二进制程序,源代码文件,man手册的位置;
 # whereis ls
ls: /bin/ls /usr/share/man/man1p/ls.1p.gz /usr/share/man/man1/ls.1.gz
NAME
       whereis - locate the binary, source, and manual page files for a command
SYNOPSIS
       whereis [-bmsu] [-BMS directory...  -f] filename...
DESCRIPTION
       whereis  locates  source/binary and manuals sections for specified files.  The supplied names are first stripped of leading pathname components and any (single) trailing extension of the form .ext, for example, .c.  Prefixes of s.  resulting from use of source code control are also dealt with.  whereis then attempts to locate the desired program in a list of standard Linux places.

OPTIONS
       -b     Search only for binaries.
       -m     Search only for manual sections.
       -s     Search only for sources.
       -B     Change or otherwise limit the places where whereis searches for binaries.
       -M     Change or otherwise limit the places where whereis searches for manual sections.
       -S     Change or otherwise limit the places where whereis searches for sources.
       -f     Terminate the last directory list and signals the start of file names, and must be used when any of the -B, -M, or -S options are used.

EXAMPLE
       Find all files in /usr/bin which are not documented in /usr/man/man1 with source in /usr/src:
              example% cd /usr/bin
              example% whereis -u -M /usr/man/man1 -S /usr/src -f *
FILES
       /{bin,sbin,etc}
       /usr/{lib,bin,old,new,local,games,include,etc,src,man,sbin,
                           X386,TeX,g++-include}
       /usr/local/{X386,TeX,X11,include,lib,man,etc,bin,games,emacs}


01.15 which命令
用于查找并显示给定指令的绝对路径
 # which vi
alias vi='vim'
    /usr/bin/vim
第一行是系统为vi设置的命令别名,第2行是vi保存的真正路径
 # which fdisk
/sbin/fdisk
which指令查找的路径是基于环境变量$PATH执行的,如果我们的指令在$PATH的一个目录下就可以被查找并显示出来,否则无法查询到;

NAME
       which - locate a command
SYNOPSIS
       which [-a] filename ...
DESCRIPTION
       which returns the pathnames of the files (or links) which would be executed in the current environment, had its arguments been given as commands in a strictly POSIX-conformant shell.  It does this by searching the PATH for executable files matching the names of the arguments. It does not follow symbolic links.

OPTIONS
       -a     print all matching pathnames of each argument

EXIT STATUS
       0      if all specified commands are found and executable
       1      if one or more specified commands is nonexistent or not executable
       2      if an invalid option is specified


01.16 file命令
用于探测给定文件的文件类型
 # file filename
file会从自己的数据库文件中查找对应的文件的文件信息;
NAME
     file — determine file type
SYNOPSIS
     file [-bchiklLNnprsvz0] [--apple] [--mime-encoding] [--mime-type] [-e testname] [-F separator] [-f namefile] [-m magicfiles] file ...
     file -C [-m magicfiles]
     file [--help]

DESCRIPTION
     file tests each argument in an attempt to classify it.  There are three sets of tests, performed in this order: filesystem tests, magic tests, and language tests.  The first test that succeeds causes the file type to be printed.

OPTIONS
     -b, --brief
             Do not prepend filenames to output lines (brief mode).
     -N, --no-pad
             Don't pad filenames so that they align in the output.
     -z, --uncompress
             Try to look inside compressed files.
     -0, --print0
             Output a null character ‘\0’ after the end of the filename.  Nice to cut(1) the output.  This does not affect the separator which is still printed.
     --help  Print a help message and exit.

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
     /dev/hda:    application/x-not-regular-file
     /dev/wd0a:   application/x-not-regular-file


01.17 touch命令
可以用来创建空文件或改变已存在文件的时间属性;
 # touch newfile
 # touch file{1,2,3,4,5,6,7,8,9}
 # touch oldfile

NAME
       touch - change file timestamps
SYNOPSIS
       touch [OPTION]... FILE...
DESCRIPTION
       Update the access and modification times of each FILE to the current time.
       A FILE argument that does not exist is created empty, unless -c or -h is supplied.
       -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
       --help display this help and exit
       --version
              output version information and exit
       Note that the -d and -t options accept different time-date formats.
DATE STRING
       The  --date=STRING  is  a  mostly  free  format  human readable date string such as "Sun, 29 Feb 2004 16:21:42 -0800" or "2004-02-29 16:21:42" or even "next Thursday".  A date string may contain items indicating calendar date, time of day, time zone, day  of  week, relative time, relative date, and numbers.  An empty string indicates the beginning of the day.  The date string format is more complex than is easily documented here but is fully described in the info documentation.


01.18 locate命令
用来查找文件的保存路径,在执行之前首先要用updatedb命令更新数据库,以后会从数据库中直接查询,因此速度会比较快;
 # updatedb
 # locate passwd
在使用locate前最好更新数据库,查找的结果才会比较准确;
NAME
       locate - find files by name
SYNOPSIS
       locate [OPTION]... PATTERN...
OPTIONS
       -b, --basename
              Match only the base name against the specified patterns.  This is the opposite of --wholename.

       -h, --help
              Write a summary of the available options to standard output and exit successfully.

       -i, --ignore-case
              Ignore case distinctions when matching patterns.
EXAMPLES
       To search for a file named exactly NAME (not *NAME*), use
              locate -b '\NAME'
       Because \ is a globbing character, this disables the implicit replacement of NAME by *NAME*.


01.19 dd命令
可以对文件进行复制并进行格式转换
 # dd if=test.sh of=new.sh //简单复制
 # dd if=test.sh conv=ucase of=new.sh //会在拷贝时转换大小写
 # dd if=/dev/cdrom of=mycd.iso //可以将光盘制作为mycd.iso文件
 # dd if=/dev/fd0 of=myfloppy.img //可以做软盘的镜像文件

01.20 updatedb命令
用于更新locate对应的数据库
第一次会比较慢,以后会比较快;

01.21 dirname命令
返回文件的路径
 # dirname /usr/bin/sort
 /usr/bin
 # dirname stdio.h
 .
在shell脚本中可能会用到

01.22 packchk命令
用来检查文件名中是否可移植
 # pathchk /etc/httpd/conf/httpd.conf
返回空表示不可移植

01.23 unlink命令
用于删除指定的普通文件并且是直接调用unlink函数删除特定文件;
不能删除目录

01.24 basename命令
用于去除文件名中的路径和后缀信息,直接获取文件名
 # basename /etc/httpd/conf/httpd.conf
httpd.conf
 # basename /etc/httpd/conf/httpd.conf .conf
httpd

01.25 rename命令
用于批量重命名文件
将file1,file2,file3,file4,file5,file6中的file批量改为linux
 # rename file linux file*
共有3个参数第1个表示替换前的部分,第2个是替换后的部分,第3个指定对哪些文件替换;