linux 文件类型识别

使用 ls -al
drwxr-xr-x.  4 root root         100 Apr 26 15:05 cpu
lrwxrwxrwx.  1 root root          13 Apr 26 15:05 fd -> /proc/self/fd
brw-rw----.  1 root disk      7,   0 Apr 26 15:05 loop0
crw-rw----.  1 root lp        6,   2 Apr 26 15:05 lp2
仔细看第一位 d代表文件目录文件，l代表链接文件，b代表块设备文件，c代表字符设备文件 
    `-\'
          regular file

    `b\'
          block special file

    `c\'
          character special file

    `C\'
          high performance ("contiguous data") file

    `d\'
          directory

    `D\'
          door (Solaris 2.5 and up)

    `l\'
          symbolic link

    `M\'
          off-line ("migrated") file (Cray DMF)

    `n\'
          network special file (HP-UX)

    `p\'
          FIFO (named pipe)

    `P\'
          port (Solaris 10 and up)

    `s\'
          socket

    `?\'
          some other file type