lib/other/popen.c

   1 /*
   2  * popen - open a pipe
   3  */
   4 /* $Header$ */
   5
   6 #include        <sys/types.h>
   7 #include        <limits.h>
   8 #include        <errno.h>
   9 #include        <signal.h>
  10 #include        <stdio.h>
  11
  12 #if     defined(__BSD4_2)
  13 union wait {
  14         int     w_status;
  15 };
  16 typedef union wait wait_arg;
  17 #else
  18 typedef int wait_arg;
  19 #endif  /* __BSD4_2 */
  20
  21 #include        "../stdio/loc_incl.h"
  22
  23 #ifdef _ANSI
  24 int _close(int d);
  25 int _dup2(int oldd, int newd);          /* not present in System 5 */
  26 int _execl(const char *name, const char *_arg, ... );
  27 pid_t _fork(void);
  28 int _pipe(int fildes[2]);
  29 pid_t _wait(wait_arg *status);
  30 void _exit(int status);
  31 #endif
  32
  33 static int pids[OPEN_MAX];
  34
  35 FILE *
  36 popen(command, type)
  37 _CONST char *command;
  38 _CONST char *type;
  39 {
  40         int piped[2];
  41         int Xtype = *type == 'r' ? 0 : *type == 'w' ? 1 : 2;
  42         int pid;
  43
  44         if (Xtype == 2 ||
  45             _pipe(piped) < 0 ||
  46             (pid = _fork()) < 0) return 0;
  47
  48         if (pid == 0) {
  49                 /* child */
  50                 register int *p;
  51
  52                 for (p = pids; p < &pids[OPEN_MAX]; p++) {
  53                         if (*p) _close((int)(p - pids));
  54                 }
  55                 _close(piped[Xtype]);
  56                 _dup2(piped[!Xtype], !Xtype);
  57                 _close(piped[!Xtype]);
  58                 _execl("/bin/sh", "sh", "-c", command, (char *) 0);
  59                 _exit(127);     /* like system() ??? */
  60         }
  61
  62         pids[piped[Xtype]] = pid;
  63         _close(piped[!Xtype]);
  64         return fdopen(piped[Xtype], type);
  65 }
  66
  67 #if     defined(__BSD4_2)
  68 #define ret_val status.w_status
  69 #else
  70 #define ret_val status
  71 #endif
  72
  73 int
  74 pclose(stream)
  75 FILE *stream;
  76 {
  77         int fd = fileno(stream);
  78         wait_arg status;
  79         int wret;
  80
  81 #ifdef _ANSI
  82         void (*intsave)(int) = signal(SIGINT, SIG_IGN);
  83         void (*quitsave)(int) = signal(SIGQUIT, SIG_IGN);
  84 #else
  85         void (*intsave)() = signal(SIGINT, SIG_IGN);
  86         void (*quitsave)() = signal(SIGQUIT, SIG_IGN);
  87 #endif
  88         fclose(stream);
  89         while ((wret = _wait(&status)) != -1) {
  90                 if (wret == pids[fd]) break;
  91         }
  92         if (wret == -1) ret_val = -1;
  93         signal(SIGINT, intsave);
  94         signal(SIGQUIT, quitsave);
  95         pids[fd] = 0;
  96         return ret_val;
  97 }
  98
  99 #if     defined(__USG)
 100 int _dup(int fildes);
 101
 102 static int
 103 _dup2(oldd, newd)
 104 int oldd, newd;
 105 {
 106         int i = 0, fd, tmp;
 107         int fdbuf[_NFILES];
 108
 109         /* ignore the error on the close() */
 110         tmp = errno; (void) _close(newd); errno = tmp;
 111         while ((fd = _dup(oldd)) != newd) {
 112                 if (fd == -1) break;
 113                 fdbuf[i++] = fd;
 114         }
 115         tmp = errno;
 116         while (--i >= 0) {
 117                 _close(fdbuf[i]);
 118         }
 119         errno = tmp;
 120         return -(fd == -1);
 121 }
 122 #endif  /* __USG */