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From: alex.bennee@linaro.org
Date: Wed, 26 Mar 2014 14:37:12 +0000
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Subject: [Qemu-devel] [RFC PATCH 2/4] qemu-log: support simple pid
	substitution in logfile
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To: qemu-devel@nongnu.org
Cc: =?UTF-8?q?Alex=20Benn=C3=A9e?= <alex.bennee@linaro.org>

From: Alex Bennée <alex.bennee@linaro.org>

When debugging stuff that occurs over several forks it would be useful
not to keep overwriting the one logfile you've set-up. This allows a
simple %d to be included once in the logfile parameter which is
substituted with getpid().

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>

diff --git a/qemu-log.c b/qemu-log.c
index 35bbb56..2897596 100644
--- a/qemu-log.c
+++ b/qemu-log.c
@@ -81,11 +81,24 @@ void do_qemu_set_log(int log_flags, bool use_own_buffers)
         qemu_log_close();
     }
 }
-
+/*
+ * Allow the user to include %d in their logfile which will be
+ * substituted with the current PID. This is useful for debugging many
+ * nested linux-user tasks but will result in lots of logs.
+ */
 void qemu_set_log_filename(const char *filename)
 {
     g_free(logfilename);
-    logfilename = g_strdup(filename);
+    if (g_strrstr(filename, "%d")) {
+        /* if we are going to format this we'd better validate first */
+        if (g_regex_match_simple("^[^%]+%d[^%]+$", filename, 0, 0)) {
+            logfilename = g_strdup_printf(filename, getpid());
+        } else {
+            g_error("Bad logfile format: %s", filename);
+        }
+    } else {
+        logfilename = g_strdup(filename);
+    }
     qemu_log_close();
     qemu_set_log(qemu_loglevel);
 }
-- 
1.9.1