pipecmd: add pipecmdarr variant.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

ccan/pipecmd/pipecmd.c

@@ -24,6 +24,20 @@ static char **gather_args(const char *arg0, va_list ap)
 }
 
 pid_t pipecmdv(int *fd_fromchild, int *fd_tochild, const char *cmd, va_list ap)
+{
+	char **arr = gather_args(cmd, ap);
+	pid_t ret;
+
+	if (!arr) {
+		errno = ENOMEM;
+		return -1;
+	}
+	ret = pipecmdarr(fd_fromchild, fd_tochild, arr);
+	free_noerr(arr);
+	return ret;
+}
+
+pid_t pipecmdarr(int *fd_fromchild, int *fd_tochild, char *const *arr)
 {
 	int tochild[2], fromchild[2], execfail[2];
 	pid_t childpid;
@@ -57,8 +71,6 @@ pid_t pipecmdv(int *fd_fromchild, int *fd_tochild, const char *cmd, va_list ap)
 		goto close_execfail_fail;
 
 	if (childpid == 0) {
-		char **args = gather_args(cmd, ap);
-
 		if (fd_tochild)
 			close(tochild[1]);
 		if (fd_fromchild)
@@ -66,9 +78,6 @@ pid_t pipecmdv(int *fd_fromchild, int *fd_tochild, const char *cmd, va_list ap)
 		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;
@@ -79,10 +88,10 @@ pid_t pipecmdv(int *fd_fromchild, int *fd_tochild, const char *cmd, va_list ap)
 				goto child_errno_fail;
 			close(fromchild[1]);
 		}
-			execvp(cmd, args);
+		execvp(arr[0], arr);
+
 	child_errno_fail:
 		err = errno;
-		}
 		write(execfail[1], &err, sizeof(err));
 		exit(127);
 	}

ccan/pipecmd/pipecmd.h

@@ -27,4 +27,12 @@ pid_t pipecmd(int *infd, int *outfd, const char *cmd, ...);
  * @ap: argument list for arguments.
  */
 pid_t pipecmdv(int *infd, int *outfd, const char *cmd, va_list ap);
+
+/**
+ * pipecmdarr - run a command, optionally connect pipes (char arry version)
+ * @infd: input fd to write to child (if non-NULL)
+ * @outfd: output fd to read from child (if non-NULL)
+ * @arr: NULL-terminated array for arguments (first is program to run).
+ */
+pid_t pipecmdarr(int *infd, int *outfd, char *const *arr);
 #endif /* CCAN_PIPECMD_H */