redirect unused fds to /dev/null in pipestream

[libi2ncommon] / src / pipestream.cpp

diff --git a/src/pipestream.cpp b/src/pipestream.cpp
index 66ee39b..b9cdcf7 100644 (file)
--- a/src/pipestream.cpp
+++ b/src/pipestream.cpp
@@ -27,6 +27,7 @@ on this file might be covered by the GNU General Public License.
 #include <errno.h>
 #include <stdio.h>
 #include <string.h>
+#include <fcntl.h>
 #include <sys/wait.h>
 #include <unistd.h>
 
@@ -203,6 +204,34 @@ mk_argv (const std::vector<std::string> &command)
     return boost::shared_array<char *> (ret);
 }
 
+/** @brief      Helper for redirecting a file descriptor to \c /dev/null.
+ *              This will only acquire an fd the first time it is called
+ *              or if it is called after unsuccessfully attempting to
+ *              acquire one.
+ *
+ *  @param fd         The open file descriptor to operate on.
+ *
+ *  @returns          \c true on success, \c false otherwise (the call to
+ *                    either \c open(2) or \c dup2(2) failed).
+ */
+static bool
+redirect_devnull (const int fd)
+{
+    static int nullfd = -1;
+    
+    errno = 0;
+    if (nullfd == -1 && (nullfd = open ("/dev/null", O_RDWR)) == -1) {
+        return false;
+    }
+
+    errno = 0;
+    if (dup2 (nullfd, fd) == -1) {
+        return false;
+    }
+
+    return true;
+}
+
 /** @brief      Helper aggregating common code for the shell-free ctors.
  *
  *  @param argv       Argument list prepared for \c execve(2).
@@ -242,14 +271,20 @@ inpipebuf::init_without_shell (const char *const *argv,
             close (pipefd [0]);
 
             if (!out) {
-                close (STDOUT_FILENO);
+                if (!redirect_devnull (STDOUT_FILENO)) {
+                    fprintf(stderr, "redirect_devnull/stdout: %m\n");
+                    /* XXX should we bail here? */
+                }
             } else if (dup2 (pipefd[1], STDOUT_FILENO) == -1) {
                 fprintf(stderr, "dup2/stdout: %m\n");
                 exit(EXIT_FAILURE);
             }
 
             if (!err) {
-                close (STDERR_FILENO);
+                if (!redirect_devnull (STDERR_FILENO)) {
+                    fprintf(stderr, "redirect_devnull/stderr: %m\n");
+                    /* XXX should we bail here? */
+                }
             } else if (dup2 (pipefd[1], STDERR_FILENO) == -1) {
                 fprintf(stderr, "dup2/stderr: %m\n");
                 exit(EXIT_FAILURE);