shell_pipe
statement: pipeline shell_pipe terminator {
| expression pipeline shell_pipe terminator {
| expression ',' expression pipeline shell_pipe terminator {
| ',' expression pipeline shell_pipe terminator {
| expression ',' expression shell_pipe terminator {
| ',' expression shell_pipe terminator {
shell_pipe: /* Empty */
shell_pipe(cmd, -1);
shell_pipe(cmd, fd);
shell_pipe(strdup(cmd), fd);