Quoth Tomi Ollila on May 26 at 11:45 am:
> With this option all writes to stderr are redirected to the spesified
> FILE (or to stdout on case FILE is '-'). This is immediately useful
> in emacs interface as some of its exec intefaces do not provide
> separation of stdout and stderr.
> ---
>  notmuch-client.h |  1 +
>  notmuch.c        | 32 ++++++++++++++++++++++++++++++++
>  2 files changed, 33 insertions(+)
> 
> diff --git a/notmuch-client.h b/notmuch-client.h
> index 45749a6..4a3c7ac 100644
> --- a/notmuch-client.h
> +++ b/notmuch-client.h
> @@ -54,6 +54,7 @@ typedef GMimeCipherContext notmuch_crypto_context_t;
>  #include <sys/stat.h>
>  #include <sys/time.h>
>  #include <unistd.h>
> +#include <fcntl.h>
>  #include <dirent.h>
>  #include <errno.h>
>  #include <signal.h>
> diff --git a/notmuch.c b/notmuch.c
> index f51a84f..654a568 100644
> --- a/notmuch.c
> +++ b/notmuch.c
> @@ -251,6 +251,32 @@ notmuch_command (notmuch_config_t *config,
>      return 0;
>  }
>  
> +static int
> +redirect_stderr (const char * stderr_file)
> +{
> +    if (strcmp (stderr_file, "-") == 0) {
> +	if (dup2 (STDOUT_FILENO, STDERR_FILENO) < 0) {
> +	    perror ("dup2");
> +	    return 1;
> +	}
> +    } else {
> +	int fd = open (stderr_file, O_WRONLY|O_CREAT|O_APPEND, 0644);

I think this should include O_TRUNC; otherwise it's too error-prone to
use programmatically.  The permissions should be 0666 (if the user's
umask says things should be group or world writable, it's not our job
to disagree).

> +	if (fd < 0) {
> +	    fprintf (stderr, "Error: Cannot redirect stderr to '%s': %s\n",
> +		     stderr_file, strerror (errno));
> +	    return 1;
> +	}
> +	if (fd != STDERR_FILENO) {
> +	    if (dup2 (fd, STDERR_FILENO) < 0) {
> +		perror ("dup2");
> +		return 1;
> +	    }
> +	    close (fd);
> +	}
> +    }
> +    return 0;
> +}
> +
>  int
>  main (int argc, char *argv[])
>  {
> @@ -259,6 +285,7 @@ main (int argc, char *argv[])
>      const char *command_name = NULL;
>      command_t *command;
>      char *config_file_name = NULL;
> +    char *stderr_file = NULL;
>      notmuch_config_t *config;
>      notmuch_bool_t print_help=FALSE, print_version=FALSE;
>      int opt_index;
> @@ -268,6 +295,7 @@ main (int argc, char *argv[])
>  	{ NOTMUCH_OPT_BOOLEAN, &print_help, "help", 'h', 0 },
>  	{ NOTMUCH_OPT_BOOLEAN, &print_version, "version", 'v', 0 },
>  	{ NOTMUCH_OPT_STRING, &config_file_name, "config", 'c', 0 },
> +	{ NOTMUCH_OPT_STRING, &stderr_file, "stderr", '\0', 0 },
>  	{ 0, 0, 0, 0, 0 }
>      };
>  
> @@ -287,6 +315,10 @@ main (int argc, char *argv[])
>  	return 1;
>      }
>  
> +    if (stderr_file && redirect_stderr (stderr_file) != 0) {
> +	/* error already printed */
> +	return 1;
> +    }
>      if (print_help)
>  	return notmuch_help_command (NULL, argc - 1, &argv[1]);
>