关于一个命令识别的问题

ctrlaltdelete

系统中的bunzip2,bzcat都是链接到bzip2的，系统是怎样识别这几个命令的呢

duanxiangqaz

联到bzip2上去，就是用的bzip2了

ctrlaltdelete

Post by duanxiangqaz
联到bzip2上去，就是用的bzip2了

但是当你单纯输入一个"bzip2"，会提示
bzip2: I won't write compressed data to a terminal.
bzip2: For help, type: `bzip2 --help'.

单纯输入"bzcat"会提示
bzcat: I won't read compressed data from a terminal.
bzcat: For help, type: `bzcat --help'.

这个是怎样实现的呢？

duanxiangqaz

Duanxiang@bb:~$ bzip2 -d

bzip2: I won't read compressed data from a terminal.

bzip2: For help, type: `bzip2 --help'.

Duanxiang@bb:~$ bzcat

bzcat: I won't read compressed data from a terminal.

bzcat: For help, type: `bzcat --help'.

duanxiangqaz

If invoked as `bzip2', default action is to compress.
              as `bunzip2',  default action is to decompress.
              as `bzcat', default action is to decompress to stdout.