Have start_command() create a pipe to read the stderr of the child.

This adds another stanza that allocates a pipe that is connected to the
child's stderr and that the caller can read from. In order to request this
pipe, the caller sets cmd->err to -1.

The implementation is not exactly modeled after the stdout case: For stdout
the caller can supply an existing file descriptor, but this facility is
nowhere needed in the stderr case. Additionally, the caller is required to
close cmd->err.

Signed-off-by: Johannes Sixt <johannes.sixt@telecom.at>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
pull/288/head
Johannes Sixt 15 years ago committed by Shawn O. Pearce
parent 477822c35d
commit f3b33f1d22
  1. 26
      run-command.c
  2. 1
      run-command.h

@ -17,8 +17,8 @@ static inline void dup_devnull(int to)
int start_command(struct child_process *cmd)
{
int need_in, need_out;
int fdin[2], fdout[2];
int need_in, need_out, need_err;
int fdin[2], fdout[2], fderr[2];
need_in = !cmd->no_stdin && cmd->in < 0;
if (need_in) {
@ -41,12 +41,26 @@ int start_command(struct child_process *cmd)
cmd->close_out = 1;
}
need_err = cmd->err < 0;
if (need_err) {
if (pipe(fderr) < 0) {
if (need_in)
close_pair(fdin);
if (need_out)
close_pair(fdout);
return -ERR_RUN_COMMAND_PIPE;
}
cmd->err = fderr[0];
}
cmd->pid = fork();
if (cmd->pid < 0) {
if (need_in)
close_pair(fdin);
if (need_out)
close_pair(fdout);
if (need_err)
close_pair(fderr);
return -ERR_RUN_COMMAND_FORK;
}
@ -73,6 +87,11 @@ int start_command(struct child_process *cmd)
close(cmd->out);
}
if (need_err) {
dup2(fderr[1], 2);
close_pair(fderr);
}
if (cmd->dir && chdir(cmd->dir))
die("exec %s: cd to %s failed (%s)", cmd->argv[0],
cmd->dir, strerror(errno));
@ -102,6 +121,9 @@ int start_command(struct child_process *cmd)
else if (cmd->out > 1)
close(cmd->out);
if (need_err)
close(fderr[1]);
return 0;
}

@ -16,6 +16,7 @@ struct child_process {
pid_t pid;
int in;
int out;
int err;
const char *dir;
const char *const *env;
unsigned close_in:1;

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