Mommy! what is PATH environment in Linux?
There is "cmd1" and "cmd.c". The cmd1 program changes PATH environment, blocks keywords which is "flag", "sh", "tmp", executes the parameter "argv[1]".
Because of the changing PATH, absolute path is needed to execute something.
There are two ways I checked.
1. Read the "flag" file with wildcard strings.
2. Read the "flag" file with soft-links.
FYI.
Initially, I thought that the current path(.) should be in the PATH environment variable in order to treat fg_tt as a relative path. But it was wrong. relative file path is available without registering current(.) path(Like above image). The reason is here(Link)