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