git.ozlabs.org Git - ccan/blob - ccan/pipecmd/pipecmd.c

   1 /* CC0 license (public domain) - see LICENSE file for details */
   2 #include <ccan/pipecmd/pipecmd.h>
   3 #include <ccan/noerr/noerr.h>
   4 #include <stdlib.h>
   5 #include <errno.h>
   6 #include <unistd.h>
   7 #include <fcntl.h>
   8
   9 static char **gather_args(const char *arg0, va_list ap)
  10 {
  11         size_t n = 1;
  12         char **arr = calloc(sizeof(char *), n + 1);
  13
  14         if (!arr)
  15                 return NULL;
  16         arr[0] = (char *)arg0;
  17
  18         while ((arr[n++] = va_arg(ap, char *)) != NULL) {
  19                 arr = realloc(arr, sizeof(char *) * (n + 1));
  20                 if (!arr)
  21                         return NULL;
  22         }
  23         return arr;
  24 }
  25
  26 pid_t pipecmdv(int *fd_fromchild, int *fd_tochild, const char *cmd, va_list ap)
  27 {
  28         int tochild[2], fromchild[2], execfail[2];
  29         pid_t childpid;
  30         int err;
  31
  32         if (fd_tochild) {
  33                 if (pipe(tochild) != 0)
  34                         goto fail;
  35         } else {
  36                 tochild[0] = open("/dev/null", O_RDONLY);
  37                 if (tochild[0] < 0)
  38                         goto fail;
  39         }
  40         if (fd_fromchild) {
  41                 if (pipe(fromchild) != 0)
  42                         goto close_tochild_fail;
  43         } else {
  44                 fromchild[1] = open("/dev/null", O_WRONLY);
  45                 if (fromchild[1] < 0)
  46                         goto close_tochild_fail;
  47         }
  48         if (pipe(execfail) != 0)
  49                 goto close_fromchild_fail;
  50
  51         if (fcntl(execfail[1], F_SETFD, fcntl(execfail[1], F_GETFD)
  52                   | FD_CLOEXEC) < 0)
  53                 goto close_execfail_fail;
  54
  55         childpid = fork();
  56         if (childpid < 0)
  57                 goto close_execfail_fail;
  58
  59         if (childpid == 0) {
  60                 char **args = gather_args(cmd, ap);
  61
  62                 if (fd_tochild)
  63                         close(tochild[1]);
  64                 if (fd_fromchild)
  65                         close(fromchild[0]);
  66                 close(execfail[0]);
  67
  68                 // Child runs command.
  69                 if (!args)
  70                         err = ENOMEM;
  71                 else {
  72                         if (tochild[0] != STDIN_FILENO) {
  73                                 if (dup2(tochild[0], STDIN_FILENO) == -1)
  74                                         goto child_errno_fail;
  75                                 close(tochild[0]);
  76                         }
  77                         if (fromchild[1] != STDOUT_FILENO) {
  78                                 if (dup2(fromchild[1], STDOUT_FILENO) == -1)
  79                                         goto child_errno_fail;
  80                                 close(fromchild[1]);
  81                         }
  82                         execvp(cmd, args);
  83                 child_errno_fail:
  84                         err = errno;
  85                 }
  86                 write(execfail[1], &err, sizeof(err));
  87                 exit(127);
  88         }
  89
  90         close(tochild[0]);
  91         close(fromchild[1]);
  92         close(execfail[1]);
  93         /* Child will close this without writing on successful exec. */
  94         if (read(execfail[0], &err, sizeof(err)) == sizeof(err)) {
  95                 waitpid(childpid, NULL, 0);
  96                 errno = err;
  97                 return -1;
  98         }
  99         if (fd_tochild)
 100                 *fd_tochild = tochild[1];
 101         if (fd_fromchild)
 102                 *fd_fromchild = fromchild[0];
 103         return childpid;
 104
 105 close_execfail_fail:
 106         close_noerr(execfail[0]);
 107         close_noerr(execfail[1]);
 108 close_fromchild_fail:
 109         if (fd_fromchild)
 110                 close_noerr(fromchild[0]);
 111         close_noerr(fromchild[1]);
 112 close_tochild_fail:
 113         close_noerr(tochild[0]);
 114         if (fd_tochild)
 115                 close_noerr(tochild[1]);
 116 fail:
 117         return -1;
 118 }
 119
 120 pid_t pipecmd(int *fd_fromchild, int *fd_tochild, const char *cmd, ...)
 121 {
 122         pid_t childpid;
 123
 124         va_list ap;
 125         va_start(ap, cmd);
 126         childpid = pipecmdv(fd_fromchild, fd_tochild, cmd, ap);
 127         va_end(ap);
 128
 129         return childpid;
 130 }