[9fans] Why getenv replaces \0 with spaces in the returned value?

[Giacomo Tesio]

Hi, last night I noticed this strange post processing in 4th edition's
getenv: 
https://github.com/brho/plan9/blob/master/sys/src/libc/9sys/getenv.c#L34-L41

        seek(f, 0, 0);
        r = read(f, ans, s);
        if(r >= 0) {
            ep = ans + s - 1;
            for(p = ans; p < ep; p++)
                if(*p == '\0')
                    *p = ' ';
            ans[s] = '\0';
        }

Anybody know why this replacement is done?
It does not seem a good fix to read/write or read/truncate races, but
I can't find a better explanation.


Giacomo