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authorUlrich Drepper <drepper@redhat.com>2002-01-18 06:26:02 +0000
committerUlrich Drepper <drepper@redhat.com>2002-01-18 06:26:02 +0000
commitb750d5e7a17cefe2ebd9f105111a62fb14d24d46 (patch)
treea29ba0feb9c541a9efa98b730175293fe7aa0e67 /manual
parente093e5b90b79f6702f068a50862e854c7f939c58 (diff)
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Update.
2002-01-16 Roger Sayle <roger@eyesopen.com> * stdlib/msort.c (msort_with_tmp): Replace implementation with more efficient "Towers of Hanoi" mergesort. (hanoi_sort, hanoi_sort_int, hanoi_sort_long): New functions, for generic, sizeof(int) and sizeof(long) variants respectively. * manial/syslog.texi (openlog): Describe possible problems with first parameter. Patch by Christopher Allen Wing <wingc@engin.umich.edu>.
Diffstat (limited to 'manual')
-rw-r--r--manual/syslog.texi64
1 files changed, 56 insertions, 8 deletions
diff --git a/manual/syslog.texi b/manual/syslog.texi
index 49f599d93f..df4179e27a 100644
--- a/manual/syslog.texi
+++ b/manual/syslog.texi
@@ -146,8 +146,7 @@ The symbols referred to in this section are declared in the file
@comment syslog.h
@comment BSD
-@deftypefun void openlog (char *@var{ident}, int @var{option},
- int @var{facility})
+@deftypefun void openlog (const char *@var{ident}, int @var{option}, int @var{facility})
@code{openlog} opens or reopens a connection to Syslog in preparation
for submitting messages.
@@ -157,6 +156,46 @@ for submitting messages.
to identify the source of the message, and people conventionally set it
to the name of the program that will submit the messages.
+If @var{ident} is NULL, or if @code{openlog} is not called, the default
+identification string used in Syslog messages will be the program name,
+taken from argv[0].
+
+Please note that the string pointer @var{ident} will be retained
+internally by the Syslog routines. You must not free the memory that
+@var{ident} points to. It is also dangerous to pass a reference to an
+automatic variable since leaving the scope would mean ending the
+lifetime of the variable. If you want to change the @var{ident} string,
+you must call @code{openlog} again; overwriting the string pointed to by
+@var{ident} is not thread-safe.
+
+You can cause the Syslog routines to drop the reference to @var{ident} and
+go back to the default string (the program name taken from argv[0]), by
+calling @code{closelog}: @xref{closelog}.
+
+In particular, if you are writing code for a shared library that might get
+loaded and then unloaded (e.g. a PAM module), and you use @code{openlog},
+you must call @code{closelog} before any point where your library might
+get unloaded, as in this example:
+
+@smallexample
+#include <syslog.h>
+
+void
+shared_library_function (void)
+@{
+ openlog ("mylibrary", option, priority);
+
+ syslog (LOG_INFO, "shared library has been invoked");
+
+ closelog ();
+@}
+@end smallexample
+
+Without the call to @code{closelog}, future invocations of @code{syslog}
+by the program using the shared library may crash, if the library gets
+unloaded and the memory containing the string @code{"mylibrary"} becomes
+unmapped. This is a limitation of the BSD syslog interface.
+
@code{openlog} may or may not open the @file{/dev/log} socket, depending
on @var{option}. If it does, it tries to open it and connect it as a
stream socket. If that doesn't work, it tries to open it and connect it
@@ -383,12 +422,21 @@ The symbols referred to in this section are declared in the file
@deftypefun void closelog (void)
@code{closelog} closes the current Syslog connection, if there is one.
-This include closing the @file{dev/log} socket, if it is open.
-
-There is very little reason to use this function. It does not flush any
-buffers; you can reopen a Syslog connection without closing it first;
-The connection gets closed automatically on exec or exit.
-@code{closelog} has primarily aesthetic value.
+This includes closing the @file{dev/log} socket, if it is open.
+@code{closelog} also sets the identification string for Syslog messages
+back to the default, if @code{openlog} was called with a non-NULL argument
+to @var{ident}. The default identification string is the program name
+taken from argv[0].
+
+If you are writing shared library code that uses @code{openlog} to
+generate custom syslog output, you should use @code{closelog} to drop the
+GNU C library's internal reference to the @var{ident} pointer when you are
+done. Please read the section on @code{openlog} for more information:
+@xref{openlog}.
+
+@code{closelog} does not flush any buffers. You do not have to call
+@code{closelog} before re-opening a Syslog connection with @code{initlog}.
+Syslog connections are automatically closed on exec or exit.
@end deftypefun