ref: c7d9da8f5a41b833946027c802e0e8d7dd014b22
dir: /sys/src/cmd/awk/popen.c/
#include <u.h> #include <libc.h> #include <bio.h> #include "awk.h" #define MAXFORKS 20 #define NSYSFILE 3 #define tst(a,b) (mode == OREAD? (b) : (a)) #define RDR 0 #define WTR 1 struct a_fork { short done; short fd; int pid; char status[128]; }; static struct a_fork the_fork[MAXFORKS]; Biobuf* popen(char *cmd, int mode) { int p[2]; int myside, hisside, pid; int i, ind; for (ind = 0; ind < MAXFORKS; ind++) if (the_fork[ind].pid == 0) break; if (ind == MAXFORKS) return nil; if(pipe(p) < 0) return nil; myside = tst(p[WTR], p[RDR]); hisside = tst(p[RDR], p[WTR]); switch (pid = fork()) { case -1: return nil; case 0: /* myside and hisside reverse roles in child */ close(myside); dup(hisside, tst(0, 1)); for (i=NSYSFILE; i<FOPEN_MAX; i++) close(i); execl("/bin/rc", "rc", "-c", cmd, nil); exits("exec failed"); default: the_fork[ind].pid = pid; the_fork[ind].fd = myside; the_fork[ind].done = 0; close(hisside); return(Bfdopen(myside, mode)); } } int pclose(Biobuf *ptr) { int f, r, ind; Waitmsg *status; f = Bfildes(ptr); Bterm(ptr); for (ind = 0; ind < MAXFORKS; ind++) if (the_fork[ind].fd == f && the_fork[ind].pid != 0) break; if (ind == MAXFORKS) return -1; if (!the_fork[ind].done) { do { if((status = wait()) == nil) r = -1; else r = status->pid; for (f = 0; f < MAXFORKS; f++) { if (r == the_fork[f].pid) { the_fork[f].done = 1; strecpy(the_fork[f].status, the_fork[f].status+512, status->msg); break; } } free(status); } while(r != the_fork[ind].pid && r != -1); if(r == -1) strcpy(the_fork[ind].status, "No loved ones to wait for"); } the_fork[ind].pid = 0; if(the_fork[ind].status[0] != '\0') return 1; return 0; }