struct cmd*
parseredirs(struct cmd *cmd, char **ps, char *es)
{
int tok;
char *q, *eq;
while(peek(ps, es, "<>")){
tok = gettoken(ps, es, 0, 0);
if(gettoken(ps, es, &q, &eq) != 'a') {
fprintf(stderr, "missing file for redirection\n");
exit(-1);
}
switch(tok){
case '<':
cmd = redircmd(cmd, mkcopy(q, eq), '<');
break;
case '>':
cmd = redircmd(cmd, mkcopy(q, eq), '>');
break;
}
}
return cmd;
}
struct cmd*
parseredirs(struct cmd *cmd, char **ps, char *es){
int tok;
char *q, *eq;
while(peek(ps, es, "<>")){
tok = gettoken(ps, es, 0, 0);
if(gettoken(ps, es, &q, &eq) != 'a')
panic("missing file for redirection");
switch(tok){
case '<':
cmd = redircmd(cmd, q, eq, O_RDONLY, 0);
break;
case '>':
cmd = redircmd(cmd, q, eq, O_WRONLY|O_CREATE, 1);
break;
case '+': // >>
cmd = redircmd(cmd, q, eq, O_WRONLY|O_CREATE, 1);
break;
}
}
return cmd;
}
/*
按字面意思理解应该是分析重定向行为的函数
*/
struct cmd*
parseredirs(struct cmd *cmd, char **ps, char *es)
{
int tok;
char *q, *eq;
while(peek(ps, es, "<>")){ //去掉前导空白符，并且判断该字符串的首字符是否是<>中的一种
tok = gettoken(ps, es, 0, 0); //如果存在 <> 符号，那么定位这个 <> 符号左面的那个指令 如 $， ps
if(gettoken(ps, es, &q, &eq) != 'a') {
fprintf(stderr, "missing file for redirection\n");
exit(-1);
}
switch(tok){
case '<':
cmd = redircmd(cmd, mkcopy(q, eq), '<');
break;
case '>':
cmd = redircmd(cmd, mkcopy(q, eq), '>');
break;
}
}
return cmd;
}
