UNIX 7th Ed. - /usr/src/libc/stdio/popen.c

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

Defined functions

Defined variables

Defined macros