1 /* @(#)popen.c 4.2 (Berkeley) 11/14/82 */ 2 #include <stdio.h> 3 #include <signal.h> 4 #define tst(a,b) (*mode == 'r'? (b) : (a)) 5 #define RDR 0 6 #define WTR 1 7 static int popen_pid[20]; 8 9 FILE * 10 popen(cmd,mode) 11 char *cmd; 12 char *mode; 13 { 14 int p[2]; 15 register myside, hisside, pid; 16 17 if(pipe(p) < 0) 18 return NULL; 19 myside = tst(p[WTR], p[RDR]); 20 hisside = tst(p[RDR], p[WTR]); 21 if((pid = fork()) == 0) { 22 /* myside and hisside reverse roles in child */ 23 close(myside); 24 dup2(hisside, tst(0, 1)); 25 close(hisside); 26 execl("/bin/sh", "sh", "-c", cmd, 0); 27 _exit(1); 28 } 29 if(pid == -1) 30 return NULL; 31 popen_pid[myside] = pid; 32 close(hisside); 33 return(fdopen(myside, mode)); 34 } 35 36 pclose(ptr) 37 FILE *ptr; 38 { 39 register f, r, (*hstat)(), (*istat)(), (*qstat)(); 40 int status; 41 42 f = fileno(ptr); 43 fclose(ptr); 44 istat = signal(SIGINT, SIG_IGN); 45 qstat = signal(SIGQUIT, SIG_IGN); 46 hstat = signal(SIGHUP, SIG_IGN); 47 while((r = wait(&status)) != popen_pid[f] && r != -1) 48 ; 49 if(r == -1) 50 status = -1; 51 signal(SIGINT, istat); 52 signal(SIGQUIT, qstat); 53 signal(SIGHUP, hstat); 54 return(status); 55 } 56