* If @errfd is NULL, the child's stderr is (write-only) /dev/null.
*
* If @errfd == @outfd (and non-NULL) they will be shared.
+ * If @infd, @outfd or @errfd is &pipecmd_preserve, it is unchanged.
*
* The return value is the pid of the child, or -1.
*/
* @arr: NULL-terminated array for arguments (first is program to run).
*/
pid_t pipecmdarr(int *infd, int *outfd, int *errfd, char *const *arr);
+
+/**
+ * pipecmd_preserve - special value for fds to indicate it is unchanged
+ */
+extern int pipecmd_preserve;
+
#endif /* CCAN_PIPECMD_H */