Linux_C bc/利用2根管道让2进程通讯

 1 /* tingbc.c
 2  * use two pipe to execute the bc.
 3  * one pipe: todc[2] , another: fromdc[2]
 4  * child thread to do dc, parent do UI
 5  */
 6 
 7 #include <stdio.h>
 8 #include <unistd.h>
 9 #include <string.h>
10 #define oops(x, n) {perror(x); exit(n);}
11 
12 void be_dc(int todc[], int fromdc[]);
13 void be_bc(int todc[], int fromdc[]);
14 int main(void) {
15   int todc[2], fromdc[2], pid;
16   if(pipe(todc)==-1 || pipe(fromdc)==-1)
17     oops("pipe", 2);
18   if((pid=fork()) == -1)
19     oops("fork" ,3);
20   if(pid==0) {
21     be_dc(todc, fromdc);//child do dc
22   }else{
23     be_bc(todc, fromdc);//parent do UI
24     wait(NULL);
25   }
26   return 0;
27 }
28 
29 void be_dc(int todc[], int fromdc[]){
30   //will do dc() , change the stdin to todc[1], change the stdout to fromdc[0]
31   close(todc[1]);
32   close(fromdc[0]);
33   if(dup2(todc[0], 0)==-1)
34     oops("could not redirect the stdin", 4);
35   if(dup2(fromdc[1], 1)==-1)
36     oops("could not redirct the stdout", 5);
37   close(todc[0]);
38   close(fromdc[1]);
39   execlp("dc", "dc", "-",NULL);
40   oops("exe",1);
41 }
42 
43 void be_bc(int todc[], int fromdc[]){
44   //will do bc(), change the stdout to todc[1], and use the fromdc[0] to read the dc‘s result
45   char cmdbuf[BUFSIZ];
46   int c1, c2;
47   char operator;
48   FILE *fout, *fread; 
49   close(todc[0]);   //donot need to todc out
50   close(fromdc[1]);  //donot need to fromdc in  
51   
52   fout=fdopen(todc[1],"w");  //write the todc[1]
53   fread=fdopen(fromdc[0],"r" );     //read the dc‘s result from fromdc[0]
54   
55   while((printf("tinybc: ")) && (fgets(cmdbuf, BUFSIZ, stdin )!=-1)) {
56     if( sscanf(cmdbuf, "%d %c %d", &c1,&operator,&c2) !=3) {
57       printf("syntax error.\n");
58       continue;
59     }
60     printf("2u cin is %d %c %d\n", c1,operator,c2);
61     if(fprintf(fout, "%d\n%d\n%c\np\n", c1,c2,operator) == EOF)//在这里有问题，c1总是读不进去，一直是0.
62       oops("fprintf", 6);
63     
64     fflush(fout);
65     if(fgets(cmdbuf, BUFSIZ, fread)==NULL)
66       break;
67     printf("%d %c %d = %s", c1, operator, c2, cmdbuf);
68   }
69   close(todc[0]);
70   close(fromdc[1]);
71 }