Linux下两个实用命令：which和whereis 的区别

Linux下的用户一般都了解的一个命令应给非man莫属吧，但怎样才能更好的发挥的它的最大效用，另一个很实用的命令whereis不得不提：

whereis：用来查询文件的二进制代码、源文件、man手册的位置等、

看一下在Linux下它的联机文档吧：

wzb55@ubuntu:~/c$ man whereis

WHEREIS(1)                                                          WHEREIS(1)



NAME  // 命令的名字-功能简介
       whereis  -  locate the binary, source, and manual page files for a com-
       mand //为一个命令（包括C语言中系统函数）定位其二进制文件，源文件 、man手册文件的位置。


SYNOPSIS  //用法大纲
       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. //只搜索二进制文件的位置

       -m     Search only for manual sections.  //只搜索man手册文件的位置

       -s     Search only for sources.     //只搜索源文件的位置

       -u     Search  for unusual entries.  A file is said to be unusual if it
              does  not  have  one  entry  of  each  requested   type.    Thus
              `whereis  -m  -u  *'  asks for those files in the current direc-
              tory which have no documentation.  //对模式取反

       -B     Change or otherwise limit the places where whereis searches  for
              binaries.  //改变或者限制 whereis 搜索目标命令二进制文件的目录（位置）

       -M     Change  or otherwise limit the places where whereis searches for
              manual sections.  //改变或者限制whereis 搜索目标命令man手册文件的目录（位置）

       -S     Change or otherwise limit the places where whereis searches  for
              sources.  //改变或者限制whereis 搜索目标命令源文件的目录（位置）

       -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}

SEE ALSO
       chdir(2V)

BUGS
       Since whereis uses chdir(2V) to run faster, pathnames  given  with  the
       -M, -S, or -B must be full; that is, they must begin with a `/'.

       whereis has a hard-coded path, so may not always find what you're look-
       ing for.

AVAILABILITY
       The whereis command is part of the util-linux-ng package and is  avail-
       able from ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.



                                  8 May 1994                        WHEREIS(1)