Teach run-command to redirect stdout to /dev/null

Some run-command callers may wish to just discard any data that
is sent to stdout from the child.  This is a lot like our existing
no_stdin support, we just open /dev/null and duplicate the descriptor
into position.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/run-command.c b/run-command.c
index d20a6ef80c08bcf51ab5e650875ba8994917ca70..eff523e191b35385895f6b077fc76c7c21819012 100644 (file)
--- a/run-command.c
+++ b/run-command.c
@@ -8,12 +8,19 @@ static inline void close_pair(int fd[2])
        close(fd[1]);
 }
 
+static inline void dup_devnull(int to)
+{
+       int fd = open("/dev/null", O_RDWR);
+       dup2(fd, to);
+       close(fd);
+}
+
 int start_command(struct child_process *cmd)
 {
-       int need_in = !cmd->no_stdin && cmd->in < 0;
-       int need_out = !cmd->stdout_to_stderr && cmd->out < 0;
+       int need_in, need_out;
        int fdin[2], fdout[2];
 
+       need_in = !cmd->no_stdin && cmd->in < 0;
        if (need_in) {
                if (pipe(fdin) < 0)
                        return -ERR_RUN_COMMAND_PIPE;
@@ -21,6 +28,9 @@ int start_command(struct child_process *cmd)
                cmd->close_in = 1;
        }
 
+       need_out = !cmd->no_stdout
+               && !cmd->stdout_to_stderr
+               && cmd->out < 0;
        if (need_out) {
                if (pipe(fdout) < 0) {
                        if (need_in)
@@ -41,11 +51,9 @@ int start_command(struct child_process *cmd)
        }
 
        if (!cmd->pid) {
-               if (cmd->no_stdin) {
-                       int fd = open("/dev/null", O_RDWR);
-                       dup2(fd, 0);
-                       close(fd);
-               } else if (need_in) {
+               if (cmd->no_stdin)
+                       dup_devnull(0);
+               else if (need_in) {
                        dup2(fdin[0], 0);
                        close_pair(fdin);
                } else if (cmd->in) {
@@ -53,7 +61,9 @@ int start_command(struct child_process *cmd)
                        close(cmd->in);
                }
 
-               if (cmd->stdout_to_stderr)
+               if (cmd->no_stdout)
+                       dup_devnull(1);
+               else if (cmd->stdout_to_stderr)
                        dup2(2, 1);
                else if (need_out) {
                        dup2(fdout[1], 1);

diff --git a/run-command.h b/run-command.h
index 1c9126b875970f9739597ef871d9ad19da2cbc14..3680ef9d452490c67788b0ab027839a8383ed855 100644 (file)
--- a/run-command.h
+++ b/run-command.h
@@ -19,6 +19,7 @@ struct child_process {
        unsigned close_in:1;
        unsigned close_out:1;
        unsigned no_stdin:1;
+       unsigned no_stdout:1;
        unsigned git_cmd:1; /* if this is to be git sub-command */
        unsigned stdout_to_stderr:1;
 };