creqs

#!/usr/bin/awk -f

# creqs: scan a c source file and determine the
#   compiler flags necessary, e.g. -lm for <math.h>

# r(h): return the required command switch to link the header `h'
# this would be a switch but apparently i cannot write
# syntactically correct switches in awk!
function r(h) {
    if (h == "math.h")
        return "-lm"
    if (h == "ncurses.h")
        return "-lncurses"
    if (h ~ /^SDL/)
        return "-l" substr(h, 5, length(h)-6)
        # length(h)-6 to trim trailing .h
    return ""
}

{   if (match($0, "^#[ \t]*include[ \t]*[\"<][ \t]*")) {
        header = substr($0, 1+RLENGTH); # trim #include < from left of line
        if (!match(header, "[ \">]")) {
            # is there a better way than | "cat 1>&2" to print to stderr?
            printf "creqs: malformed #include directive: `%s'\n", $0 | "cat 1>&2"
            next
        }
        header = substr(header, 1, RSTART-1); # trim to the actual name of the header
        if (switch = r(header))
            reqs = reqs? reqs " " switch: switch
    }
}

END { print reqs }