uid.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

#include <u.h>
#include <libc.h>

/*
 * /adm/users is
 *	id:user/group:head member:other members
 *
 * /etc/{passwd,group}
 *	name:x:nn:other stuff
 */

static int isnumber(char *s);

sniff(Biobuf *b)
{
	read first line of file into p;

	nf = getfields(p, f, nelem(f), ":");
	if(nf < 4)
		return nil;

	if(isnumber(f[0]) && !isnumber(f[2]))
		return _plan9;

	if(!isnumber(f[0]) && isnumber(f[2]))
		return _unix;

	return nil;
}


int
isnumber(char *s)
{
	char *q;

	strtol(s, &q, 10);
	return *q == '\0';
}

/* EOF */