pipecmd: new module.

[ccan] / ccan / pipecmd / pipecmd.c

diff --git a/ccan/pipecmd/pipecmd.c b/ccan/pipecmd/pipecmd.c
new file mode 100644 (file)
index 0000000..352677f
--- /dev/null
+++ b/ccan/pipecmd/pipecmd.c
@@ -0,0 +1,130 @@
+/* CC0 license (public domain) - see LICENSE file for details */
+#include <ccan/pipecmd/pipecmd.h>
+#include <ccan/noerr/noerr.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <unistd.h>
+#include <fcntl.h>
+
+static char **gather_args(const char *arg0, va_list ap)
+{
+       size_t n = 1;
+       char **arr = calloc(sizeof(char *), n + 1);
+
+       if (!arr)
+               return NULL;
+       arr[0] = (char *)arg0;
+
+       while ((arr[n++] = va_arg(ap, char *)) != NULL) {
+               arr = realloc(arr, sizeof(char *) * (n + 1));
+               if (!arr)
+                       return NULL;
+       }
+       return arr;
+}
+
+pid_t pipecmdv(int *fd_fromchild, int *fd_tochild, const char *cmd, va_list ap)
+{
+       int tochild[2], fromchild[2], execfail[2];
+       pid_t childpid;
+       int err;
+
+       if (fd_tochild) {
+               if (pipe(tochild) != 0)
+                       goto fail;
+       } else {
+               tochild[0] = open("/dev/null", O_RDONLY);
+               if (tochild[0] < 0)
+                       goto fail;
+       }
+       if (fd_fromchild) {
+               if (pipe(fromchild) != 0)
+                       goto close_tochild_fail;
+       } else {
+               fromchild[1] = open("/dev/null", O_WRONLY);
+               if (fromchild[1] < 0)
+                       goto close_tochild_fail;
+       }
+       if (pipe(execfail) != 0)
+               goto close_fromchild_fail;
+
+       if (fcntl(execfail[1], F_SETFD, fcntl(execfail[1], F_GETFD)
+                 | FD_CLOEXEC) < 0)
+               goto close_execfail_fail;
+
+       childpid = fork();
+       if (childpid < 0)
+               goto close_execfail_fail;
+
+       if (childpid == 0) {
+               char **args = gather_args(cmd, ap);
+
+               if (fd_tochild)
+                       close(tochild[1]);
+               if (fd_fromchild)
+                       close(fromchild[0]);
+               close(execfail[0]);
+
+               // Child runs command.
+               if (!args)
+                       err = ENOMEM;
+               else {
+                       if (tochild[0] != STDIN_FILENO) {
+                               if (dup2(tochild[0], STDIN_FILENO) == -1)
+                                       goto child_errno_fail;
+                               close(tochild[0]);
+                       }
+                       if (fromchild[1] != STDOUT_FILENO) {
+                               if (dup2(fromchild[1], STDOUT_FILENO) == -1)
+                                       goto child_errno_fail;
+                               close(fromchild[1]);
+                       }
+                       execvp(cmd, args);
+               child_errno_fail:
+                       err = errno;
+               }
+               write(execfail[1], &err, sizeof(err));
+               exit(127);
+       }
+
+       close(tochild[0]);
+       close(fromchild[1]);
+       close(execfail[1]);
+       /* Child will close this without writing on successful exec. */
+       if (read(execfail[0], &err, sizeof(err)) == sizeof(err)) {
+               waitpid(childpid, NULL, 0);
+               errno = err;
+               return -1;
+       }
+       if (fd_tochild)
+               *fd_tochild = tochild[1];
+       if (fd_fromchild)
+               *fd_fromchild = fromchild[0];
+       return childpid;
+
+close_execfail_fail:
+       close_noerr(execfail[0]);
+       close_noerr(execfail[1]);
+close_fromchild_fail:
+       if (fd_fromchild)
+               close_noerr(fromchild[0]);
+       close_noerr(fromchild[1]);
+close_tochild_fail:
+       close_noerr(tochild[0]);
+       if (fd_tochild)
+               close_noerr(tochild[1]);
+fail:
+       return -1;
+}
+
+pid_t pipecmd(int *fd_fromchild, int *fd_tochild, const char *cmd, ...)
+{
+       pid_t childpid;
+
+       va_list ap;
+       va_start(ap, cmd);
+       childpid = pipecmdv(fd_fromchild, fd_tochild, cmd, ap);
+       va_end(ap);
+
+       return childpid;
+}