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 int pipecmd_preserve;
  10
  11 static char **gather_args(const char *arg0, va_list ap)
  12 {
  13         size_t n = 1;
  14         char **arr = calloc(sizeof(char *), n + 1);
  15
  16         if (!arr)
  17                 return NULL;
  18         arr[0] = (char *)arg0;
  19
  20         while ((arr[n++] = va_arg(ap, char *)) != NULL) {
  21                 char **narr = realloc(arr, sizeof(char *) * (n + 1));
  22                 if (!narr) {
  23                         free(arr);
  24                         return NULL;
  25                 }
  26                 arr = narr;
  27         }
  28         return arr;
  29 }
  30
  31 pid_t pipecmdv(int *fd_tochild, int *fd_fromchild, int *fd_errfromchild,
  32                const char *cmd, va_list ap)
  33 {
  34         char **arr = gather_args(cmd, ap);
  35         pid_t ret;
  36
  37         if (!arr) {
  38                 errno = ENOMEM;
  39                 return -1;
  40         }
  41         ret = pipecmdarr(fd_tochild, fd_fromchild, fd_errfromchild, arr);
  42         free_noerr(arr);
  43         return ret;
  44 }
  45
  46 pid_t pipecmdarr(int *fd_tochild, int *fd_fromchild, int *fd_errfromchild,
  47                  char *const *arr)
  48 {
  49         int tochild[2], fromchild[2], errfromchild[2], execfail[2];
  50         pid_t childpid;
  51         int err;
  52
  53         if (fd_tochild) {
  54                 if (fd_tochild == &pipecmd_preserve) {
  55                         tochild[0] = STDIN_FILENO;
  56                         fd_tochild = NULL;
  57                 } else if (pipe(tochild) != 0)
  58                         goto fail;
  59         } else {
  60                 tochild[0] = open("/dev/null", O_RDONLY);
  61                 if (tochild[0] < 0)
  62                         goto fail;
  63         }
  64         if (fd_fromchild) {
  65                 if (fd_fromchild == &pipecmd_preserve) {
  66                         fromchild[1] = STDOUT_FILENO;
  67                         fd_fromchild = NULL;
  68                 } else if (pipe(fromchild) != 0)
  69                         goto close_tochild_fail;
  70         } else {
  71                 fromchild[1] = open("/dev/null", O_WRONLY);
  72                 if (fromchild[1] < 0)
  73                         goto close_tochild_fail;
  74         }
  75         if (fd_errfromchild) {
  76                 if (fd_errfromchild == &pipecmd_preserve) {
  77                         errfromchild[1] = STDERR_FILENO;
  78                         fd_errfromchild = NULL;
  79                 } else if (fd_errfromchild == fd_fromchild) {
  80                         errfromchild[0] = fromchild[0];
  81                         errfromchild[1] = fromchild[1];
  82                 } else {
  83                         if (pipe(errfromchild) != 0)
  84                                 goto close_fromchild_fail;
  85                 }
  86         } else {
  87                 errfromchild[1] = open("/dev/null", O_WRONLY);
  88                 if (errfromchild[1] < 0)
  89                         goto close_fromchild_fail;
  90         }
  91
  92         if (pipe(execfail) != 0)
  93                 goto close_errfromchild_fail;
  94
  95         if (fcntl(execfail[1], F_SETFD, fcntl(execfail[1], F_GETFD)
  96                   | FD_CLOEXEC) < 0)
  97                 goto close_execfail_fail;
  98
  99         childpid = fork();
 100         if (childpid < 0)
 101                 goto close_execfail_fail;
 102
 103         if (childpid == 0) {
 104                 if (fd_tochild)
 105                         close(tochild[1]);
 106                 if (fd_fromchild)
 107                         close(fromchild[0]);
 108                 if (fd_errfromchild && fd_errfromchild != fd_fromchild)
 109                         close(errfromchild[0]);
 110
 111                 close(execfail[0]);
 112
 113                 // Child runs command.
 114                 if (tochild[0] != STDIN_FILENO) {
 115                         if (dup2(tochild[0], STDIN_FILENO) == -1)
 116                                 goto child_errno_fail;
 117                         close(tochild[0]);
 118                 }
 119                 if (fromchild[1] != STDOUT_FILENO) {
 120                         if (dup2(fromchild[1], STDOUT_FILENO) == -1)
 121                                 goto child_errno_fail;
 122                         close(fromchild[1]);
 123                 }
 124                 if (fd_errfromchild && fd_errfromchild == fd_fromchild) {
 125                         if (dup2(STDOUT_FILENO, STDERR_FILENO) == -1)
 126                                 goto child_errno_fail;
 127                 } else if (errfromchild[1] != STDERR_FILENO) {
 128                         if (dup2(errfromchild[1], STDERR_FILENO) == -1)
 129                                 goto child_errno_fail;
 130                         close(errfromchild[1]);
 131                 }
 132                 execvp(arr[0], arr);
 133
 134         child_errno_fail:
 135                 err = errno;
 136                 /* Gcc's warn-unused-result fail. */
 137                 if (write(execfail[1], &err, sizeof(err))) {
 138                         ;
 139                 }
 140                 exit(127);
 141         }
 142
 143         close(tochild[0]);
 144         close(fromchild[1]);
 145         close(errfromchild[1]);
 146         close(execfail[1]);
 147         /* Child will close this without writing on successful exec. */
 148         if (read(execfail[0], &err, sizeof(err)) == sizeof(err)) {
 149                 close(execfail[0]);
 150                 waitpid(childpid, NULL, 0);
 151                 errno = err;
 152                 return -1;
 153         }
 154         close(execfail[0]);
 155         if (fd_tochild)
 156                 *fd_tochild = tochild[1];
 157         if (fd_fromchild)
 158                 *fd_fromchild = fromchild[0];
 159         if (fd_errfromchild)
 160                 *fd_errfromchild = errfromchild[0];
 161         return childpid;
 162
 163 close_execfail_fail:
 164         close_noerr(execfail[0]);
 165         close_noerr(execfail[1]);
 166 close_errfromchild_fail:
 167         if (fd_errfromchild)
 168                 close_noerr(errfromchild[0]);
 169         close_noerr(errfromchild[1]);
 170 close_fromchild_fail:
 171         if (fd_fromchild)
 172                 close_noerr(fromchild[0]);
 173         close_noerr(fromchild[1]);
 174 close_tochild_fail:
 175         close_noerr(tochild[0]);
 176         if (fd_tochild)
 177                 close_noerr(tochild[1]);
 178 fail:
 179         return -1;
 180 }
 181
 182 pid_t pipecmd(int *fd_tochild, int *fd_fromchild, int *fd_errfromchild,
 183               const char *cmd, ...)
 184 {
 185         pid_t childpid;
 186
 187         va_list ap;
 188         va_start(ap, cmd);
 189         childpid = pipecmdv(fd_tochild, fd_fromchild, fd_errfromchild, cmd, ap);
 190         va_end(ap);
 191
 192         return childpid;
 193 }