why wrong file descriptor ??
hi friends,
its all code, but not getting why it is telling wrong descriptor.
Code:
1 //redirecting output of ls -l command to wc, with help of tmp file
2
3 #include<stdio.h>
4 #include<fcntl.h>
5
6
7 void main()
8 {
9 int fd ;
10 switch(fork())
11 {
12 default : break ;
13
14 case -1 : fprintf(stderr, "system error\n") ;
15 exit(1) ;
16 case 0 : if((fd = open("tmp", O_CREAT|O_WRONLY,0600\
17 )) == -1)
18 {
19 perror("open") ;
20 printf("Couldn't create tmp file\n") ;
21 exit(2) ;
22 }
23
24 close(1) ; // closing 1 row
25 if(dup(fd) != 1)
26 {
27 fprintf(stderr, " Dup error...");
28 exit(3) ;
29
30 }
31 close(fd) ; // closing the extra file des
32 execl("/bin/ls","ls","-l", NULL) ;
33 fprintf(stderr,"error exit 4") ;
34 } // end of switch
35
36 switch(fork()) // this fork for wc
37 {
38 case -1 : // if not able to fork
39 break;
40 case 0 :if((fd = open("tmp", O_CREAT|O_WRONLY,0600\
41 )) == -1)
42 {
43 perror("open") ;
44 printf("Couldn't create tmp file\n") ;
45 exit(2) ;
46 }
47
48 close(0); // freeing the 0th row in file table
49
50 //printf("fd = %d\n", dup(fd)) ;
51 //close(0) ;
52 if(dup(fd) != 0)
53 {
54 fprintf(stderr," wc input error(dup)");
55 exit(4) ;
56 }
57
58 // close(fd) ;
59 execl("/usr/bin/wc", "wc",NULL) ;
60 fprintf(stderr, "error wc exit 5");
61 exit(5) ;
62 }// end of wc switch
63
64
65
66 wait(NULL) ;
67 exit(0) ;
68 }// end of main
