shprint.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	"mk.h"

static char *vexpand(char*, Envy*, Bufblock*);
static char *shquote(char*, Rune, Bufblock*);
static char *shbquote(char*, Bufblock*);

void
shprint(char *s, Envy *env, Bufblock *buf)
{
	int n;
	Rune r;

	while(*s) {
		n = chartorune(&r, s);
		if (r == '$')
			s = vexpand(s, env, buf);
		else {
			rinsert(buf, r);
			s += n;
			s = copyq(s, r, buf);	/*handle quoted strings*/
		}
	}
	insert(buf, 0);
}

static char *
mygetenv(char *name, Envy *env)
{
	if (!env)
		return 0;
	if (symlook(name, S_WESET, 0) == 0 && symlook(name, S_INTERNAL, 0) == 0)
		return 0;
		/* only resolve internal variables and variables we've set */
	for(; env->name; env++){
		if (strcmp(env->name, name) == 0)
			return wtos(env->values, ' ');
	}
	return 0;
}

static char *
vexpand(char *w, Envy *env, Bufblock *buf)
{
	char *s, carry, *p, *q;

	assert(/*vexpand no $*/ *w == '$');
	p = w+1;	/* skip dollar sign */
	if(*p == '{') {
		p++;
		q = utfrune(p, '}');
		if (!q)
			q = strchr(p, 0);
	} else
		q = shname(p);
	carry = *q;
	*q = 0;
	s = mygetenv(p, env);
	*q = carry;
	if (carry == '}')
		q++;
	if (s) {
		bufcpy(buf, s, strlen(s));
		free(s);
	} else 		/* copy name intact*/
		bufcpy(buf, w, q-w);
	return(q);
}

void
front(char *s)
{
	char *t, *q;
	int i, j;
	char *flds[512];

	q = strdup(s);
	i = getfields(q, flds, 512, 0, " \t\n");
	if(i > 5){
		flds[4] = flds[i-1];
		flds[3] = "...";
		i = 5;
	}
	t = s;
	for(j = 0; j < i; j++){
		for(s = flds[j]; *s; *t++ = *s++);
		*t++ = ' ';
	}
	*t = 0;
	free(q);
}