Teach run_command how to setup a stdin pipe

Sometimes callers trying to use run_command to execute a child
process will want to setup a pipe or file descriptor to redirect
into the child's stdin.

This idea is completely stolen from builtin-bundle's fork_with_pipe,
written by Johannes Schindelin.  All credit (and blame) should lie
with Dscho.  ;-)

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 a866a0669426f0f1c94bee92d3b78d191209c28b..03ff7bcac2a812bfa049255b499f25fdc14a0fd4 100644 (file)
--- a/run-command.c
+++ b/run-command.c
@@ -4,15 +4,39 @@
 
 int start_command(struct child_process *cmd)
 {
+       int need_in = !cmd->no_stdin && cmd->in < 0;
+       int fdin[2];
+
+       if (need_in) {
+               if (pipe(fdin) < 0)
+                       return -ERR_RUN_COMMAND_PIPE;
+               cmd->in = fdin[1];
+               cmd->close_in = 1;
+       }
+
        cmd->pid = fork();
-       if (cmd->pid < 0)
+       if (cmd->pid < 0) {
+               if (need_in) {
+                       close(fdin[0]);
+                       close(fdin[1]);
+               }
                return -ERR_RUN_COMMAND_FORK;
+       }
+
        if (!cmd->pid) {
                if (cmd->no_stdin) {
                        int fd = open("/dev/null", O_RDWR);
                        dup2(fd, 0);
                        close(fd);
+               } else if (need_in) {
+                       dup2(fdin[0], 0);
+                       close(fdin[0]);
+                       close(fdin[1]);
+               } else if (cmd->in) {
+                       dup2(cmd->in, 0);
+                       close(cmd->in);
                }
+
                if (cmd->stdout_to_stderr)
                        dup2(2, 1);
                if (cmd->git_cmd) {
@@ -22,11 +46,20 @@ int start_command(struct child_process *cmd)
                }
                die("exec %s failed.", cmd->argv[0]);
        }
+
+       if (need_in)
+               close(fdin[0]);
+       else if (cmd->in)
+               close(cmd->in);
+
        return 0;
 }
 
 int finish_command(struct child_process *cmd)
 {
+       if (cmd->close_in)
+               close(cmd->in);
+
        for (;;) {
                int status, code;
                pid_t waiting = waitpid(cmd->pid, &status, 0);

diff --git a/run-command.h b/run-command.h
index 24cdb4eb190b6bea844e7c674ea4caf32462caa0..ff090679a6fecd66bda4fba804a8ab6555571aa9 100644 (file)
--- a/run-command.h
+++ b/run-command.h
@@ -4,6 +4,7 @@
 enum {
        ERR_RUN_COMMAND_FORK = 10000,
        ERR_RUN_COMMAND_EXEC,
+       ERR_RUN_COMMAND_PIPE,
        ERR_RUN_COMMAND_WAITPID,
        ERR_RUN_COMMAND_WAITPID_WRONG_PID,
        ERR_RUN_COMMAND_WAITPID_SIGNAL,
@@ -13,6 +14,8 @@ enum {
 struct child_process {
        const char **argv;
        pid_t pid;
+       int in;
+       unsigned close_in:1;
        unsigned no_stdin:1;
        unsigned git_cmd:1; /* if this is to be git sub-command */
        unsigned stdout_to_stderr:1;