命令的輸出與其符號連結的輸出不匹配

我在我的樹莓派上使用 RASPBIAN。我發現命令“apropos”是命令“wahtis”的符號連結。但是，當使用相同的參數時，這些命令的輸出不匹配：

$ whatis delete
delete: nothing appropriate.

但

$ apropos delete
argz_delete (3)      - functions to handle an argz list
delete_module (2)    - unload a kernel module
dphys-swapfile (8)   - set up, mount/unmount, and delete an swap file
git-branch (1)       - List, create, or delete branches
git-replace (1)      - Create, list, delete refs to replace objects
git-symbolic-ref (1) - Read, modify and delete symbolic refs
git-tag (1)          - Create, list, delete or verify a tag object signed 
***output is truncated to save space....***

很明顯，apropos 是 whatis 的符號連結。

pi@raspberry:~ $ which apropos
/usr/bin/apropos
pi@raspberry:~ $ ls -l /usr/bin/apropos
lrwxrwxrwx 1 root root 6 Aug 24  2017 /usr/bin/apropos -> whatis

怎麼會這樣？

正在執行的執行檔將知道完整的呼叫命令行，並且可以根據呼叫它的名稱修改其行為。對於apropos/的具體實例whatis，您可以在原始碼（連結的最新版本的第 895 行附近）中看到，首先要做的是確定命令是否被名稱呼叫apropos：

int main (int argc, char *argv[])
{
#ifdef HAVE_ICONV
   char *locale_charset;
#endif
   int status = OK;

   program_name = base_name (argv[0]);
   if (STREQ (program_name, APROPOS_NAME)) {
       am_apropos = 1;
       argp_program_version = "apropos " PACKAGE_VERSION;
   } else {

在處理過程中還有大約十幾個地方檢查am_apropos標誌，並且根據它是否已設置而表現不同。

引用自：https://unix.stackexchange.com/questions/440987