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         char **arr = gather_args(cmd, ap);
  29         pid_t ret;
  30
  31         if (!arr) {
  32                 errno = ENOMEM;
  33                 return -1;
  34         }
  35         ret = pipecmdarr(fd_fromchild, fd_tochild, arr);
  36         free_noerr(arr);
  37         return ret;
  38 }
  39
  40 pid_t pipecmdarr(int *fd_fromchild, int *fd_tochild, char *const *arr)
  41 {
  42         int tochild[2], fromchild[2], execfail[2];
  43         pid_t childpid;
  44         int err;
  45
  46         if (fd_tochild) {
  47                 if (pipe(tochild) != 0)
  48                         goto fail;
  49         } else {
  50                 tochild[0] = open("/dev/null", O_RDONLY);
  51                 if (tochild[0] < 0)
  52                         goto fail;
  53         }
  54         if (fd_fromchild) {
  55                 if (pipe(fromchild) != 0)
  56                         goto close_tochild_fail;
  57         } else {
  58                 fromchild[1] = open("/dev/null", O_WRONLY);
  59                 if (fromchild[1] < 0)
  60                         goto close_tochild_fail;
  61         }
  62         if (pipe(execfail) != 0)
  63                 goto close_fromchild_fail;
  64
  65         if (fcntl(execfail[1], F_SETFD, fcntl(execfail[1], F_GETFD)
  66                   | FD_CLOEXEC) < 0)
  67                 goto close_execfail_fail;
  68
  69         childpid = fork();
  70         if (childpid < 0)
  71                 goto close_execfail_fail;
  72
  73         if (childpid == 0) {
  74                 if (fd_tochild)
  75                         close(tochild[1]);
  76                 if (fd_fromchild)
  77                         close(fromchild[0]);
  78                 close(execfail[0]);
  79
  80                 // Child runs command.
  81                 if (tochild[0] != STDIN_FILENO) {
  82                         if (dup2(tochild[0], STDIN_FILENO) == -1)
  83                                 goto child_errno_fail;
  84                         close(tochild[0]);
  85                 }
  86                 if (fromchild[1] != STDOUT_FILENO) {
  87                         if (dup2(fromchild[1], STDOUT_FILENO) == -1)
  88                                 goto child_errno_fail;
  89                         close(fromchild[1]);
  90                 }
  91                 execvp(arr[0], arr);
  92
  93         child_errno_fail:
  94                 err = errno;
  95                 write(execfail[1], &err, sizeof(err));
  96                 exit(127);
  97         }
  98
  99         close(tochild[0]);
 100         close(fromchild[1]);
 101         close(execfail[1]);
 102         /* Child will close this without writing on successful exec. */
 103         if (read(execfail[0], &err, sizeof(err)) == sizeof(err)) {
 104                 waitpid(childpid, NULL, 0);
 105                 errno = err;
 106                 return -1;
 107         }
 108         if (fd_tochild)
 109                 *fd_tochild = tochild[1];
 110         if (fd_fromchild)
 111                 *fd_fromchild = fromchild[0];
 112         return childpid;
 113
 114 close_execfail_fail:
 115         close_noerr(execfail[0]);
 116         close_noerr(execfail[1]);
 117 close_fromchild_fail:
 118         if (fd_fromchild)
 119                 close_noerr(fromchild[0]);
 120         close_noerr(fromchild[1]);
 121 close_tochild_fail:
 122         close_noerr(tochild[0]);
 123         if (fd_tochild)
 124                 close_noerr(tochild[1]);
 125 fail:
 126         return -1;
 127 }
 128
 129 pid_t pipecmd(int *fd_fromchild, int *fd_tochild, const char *cmd, ...)
 130 {
 131         pid_t childpid;
 132
 133         va_list ap;
 134         va_start(ap, cmd);
 135         childpid = pipecmdv(fd_fromchild, fd_tochild, cmd, ap);
 136         va_end(ap);
 137
 138         return childpid;
 139 }