The "cmd1_TT" is the program that executes inputted one argument(argv[1]) and deletes environment variable PATH. "echo123" is soft-link of original echo.
The "echo123" works when current path is registered("export") or current path(./) is stated.
But see this.
The "fg_tt" is the text file in the /tmp But it works without current path. Because The "fg_tt" is not an executable file. Also the shell's autocomplete(Tab) is not related to PATH. Only executable files are affected by the PATH environment variable.
| Check environment | |||
| O S | Ubuntu 16.04.1 LTS | CPU | Intel i5 2.80 GHz |
| SHELL | GNU bash 4.3.46(1) | GPU | - |
| RAM | 8 GB | ||