Question

I over heard someone saying that system() call from libc is not safe.

One reason i can think of is that it launches shell utility e.g. /bin/bash and if system("rm -rf $input") is started and $input is un-sanitized user input then it can potentially wreck havoc if $input=”/”.
What are the other reasons?

Answer 1

In general, “safe” is by comparison to the exec family of system calls (execve() being the lowest level standard one); involving a shell not only means problems with unsanitized data but also with $PATH (do you know what you are executing?) and with $IFS (this is a fun one: if someone can change $IFS on you, the shell won’t parse things the way you expect).