3 ms·
To be fair, that's not actually in the book. I said it was based on a function from that book, but below is the version they actually write in the book; I apolo
by trealira 2y ago
To be fair, that's not actually in the book. I said it was based on a function from that book, but below is the version they actually write in the book; I apologize for unintentionally misleading you. I wrote the above function myself (based on this one below) to showcase the type of style I'm talking about.
/* getline: read a line into s, return length */
int getline(char s[], int lim)
{
int c, i;
for (i=O; i<lim-1 && (c=getchar())!=EOF && c!='\n'; ++i)
s[i] = c;
if (c == '\n') {
s[i] = c;
++i;
}
s[i] = '\0';
return i;
}
They specifically don't use pointer arithmetic or the post-increment operator, because at that point in the book, they haven't introduced those yet.
However, that function I wrote isn't far off from the real Unix V7 version of fgets [0], which is a similar function to getline:
char *
fgets(s, n, iop)
char *s;
register FILE *iop;
{
register c;
register char *cs;
cs = s;
while (--n>0 && (c = getc(iop))>=0) {
*cs++ = c;
if (c=='\n')
break;
}
if (c<0 && cs==s)
return(NULL);
*cs++ = '\0';
return(s);
}
Like I said, the creators and first users of C seemed to really like expressions with side-effects, pointer arithmetic, and while-loops with empty bodies (though fgets doesn't have that). It's interesting how Go is different in this regard, considering Ken Thompson was a co-creator of both languages.
[0]: https://minnie.tuhs.org/cgi-bin/utree.pl?file=V7/usr/src/libc/stdio/fgets.c https://minnie.tuhs.org/cgi-bin/utree.pl?file=V7/usr/src/lib...