I'm doing some testing with an on-screen colorizer library I wrote, which does some PTY manipulation, captures screen output, and renders certain regex patterns in certain colors. It's designed to help testers notice certain keywords in a test environment that is not easily automated.
On bash 4.3.36 on Ubuntu 16.04 LTS, I've noticed that all commands seem to fork() a separate process, even shell builtins. This makes it easy to detect the start of any command by hooking fork() in libc. However, on bash 4.3.11 on Ubuntu 14.04 LTS, this behavior is not observed (ie: only "disk commands" cause a fork(), while builtins do not trigger a fork). Additionally, when running in a non-interactive bash instance, shell builtins never cause a fork, regardless of whether I'm running a script (ie: ./test.sh), or using bash via the "-c" option (ie: bash -c "ls; ls -la"). Is there any way, either via environment variables, BASHRC settings, or bash startup flags, or some other means (ie: not recompiling bash) where I can: 1) Have bash 4.3.11 fork() for every interactive command, like in bash 4.3.36. 2) Have both bash 4.3.11 and 4.3.36 trigger a fork() for builtins being executed in a non-interactive shell? I could potentially use PROMPT_COMMAND to detect the most recent command, "type" it, and force running in a subshell, but I want to avoid breaking other scripts by changing how commands are actually executed, save for forking. On a side note, its interesting how bash 4.3.36 does this, even for the "cd" command, since launching it in a subshell can't change the CWD for the parent process. Thank you. ============================================================ Matthew Giassa, MASc, BASc, EIT Security and Embedded Systems Specialist e-mail: matt...@giassa.net website: www.giassa.net
