grep is from AT&T Unix version 6. awk is from AT&T Unix version 7. Bash is from Gnu but the script is actually plain old Bourne Shell from AT&T Unix version 7.
It wouldn't necessarily make it Bash. That would mean using actual Bash features. It's still non-portable sh, because it relies on an extra program being available, but it isn't relying on Bash itself - none of expansions or so on.
Actually, "${name-word}" has been part of the Bourne shell since the beginning, and the "${name:-word}" extension is specified in recent versions of the POSIX standard...
"AWK was significantly revised and expanded in 1985–88, resulting in the GNU AWK implementation written by Paul Rubin, Jay Fenlason, and Richard Stallman, released in 1988.[8] GNU AWK may be the most widely deployed version" AWK wikipedia entry
If you are on linux, you are using GNU grep, not unix grep.
Others have addressed bash... so wrong on all counts.
