dtmsglogopenfile(3) [hpux man page]
DtMsgLogOpenFile(library call) DtMsgLogOpenFile(library call) NAME
DtMsgLogOpenFile -- opens a log file SYNOPSIS
#include <Dt/MsgLog.h> FILE* DtMsgLogOpenFile( const char* type, char** filename_return); DESCRIPTION
The DtMsgLogOpenFile function calls fopen to open a log file with type open mode. If fopen opens a log file successfully and returns a non- NULL filename_return, DtMsgLogOpenFile calls malloc to allocate space for filename_return. DtMsgLogOpenFile then copies the log file name to filename_return. The caller must use the free function to release the space allocated for filename_return, if it is not NULL. The caller must also close the file pointer returned by DtMsgLogOpenFile. Use caution in doing this because stderr may be returned. For a description of the algorithm used to determine the log file to open, see DtMsgLogMessage(3). Note that if a log file cannot be opened, filename_return will be set to NULL. ARGUMENTS
type Specifies the file open flag. See fopen(3) for more information. filename_return Specifies the variable to receive the returned log file name. ENVIRONMENT VARIABLES
None. RESOURCES
None. ACTIONS
/MESSAGES None. ERRORS
/WARNINGS None. EXAMPLES
The following code fragment opens the log file, logs the log file name, closes the file, and frees the space allocated for the file name. char * log_file; FILE * fp = DtMsgLogOpenFile ("a+", &log_file); if (log_file) { DtMsgLogMessage (argv[0], DtMsgLogInformation, "The log file name is: %s", log_file); free (log_file); } if (fp && fp != stderr) fclose (fp); RETURN VALUE
If DtMsgLogMessage completes successfully, it returns a pointer to the opened log file. If it cannot open a log file, it returns stderr. FILES
None. SEE ALSO
DtMsgLogMessage(3), DtMsgLogSetHandler(3) DtMsgLogOpenFile(library call)
Check Out this Related Man Page
wrap_log_reader(3erl) Erlang Module Definition wrap_log_reader(3erl) NAME
wrap_log_reader - A function to read internally formatted wrap disk logs DESCRIPTION
wrap_log_reader is a function to read internally formatted wrap disk logs, refer to disk_log(3erl). wrap_log_reader does not interfere with disk_log activities; there is however a known bug in this version of the wrap_log_reader , see chapter bugs below. A wrap disk log file consists of several files, called index files. A log file can be opened and closed. It is also possible to open just one index file separately. If an non-existent or a non-internally formatted file is opened, an error message is returned. If the file is corrupt, no attempt to repair it will be done but an error message is returned. If a log is configured to be distributed, there is a possibility that all items are not loggen on all nodes. wrap_log_reader does only read the log on the called node, it is entirely up to the user to be sure that all items are read. EXPORTS
chunk(Continuation) chunk(Continuation, N) -> {Continuation2, Terms} | {Continuation2, Terms, Badbytes} | {Continuation2, eof} | {error, Reason} Types Continuation = continuation() N = int() > 0 | infinity Continuation2 = continuation() Terms= [term()] Badbytes = integer() This function makes it possible to efficiently read the terms which have been appended to a log. It minimises disk I/O by reading large 8K chunks from the file. The first time chunk is called an initial continuation returned from the open/1 , open/2 must be provided. When chunk/3 is called, N controls the maximum number of terms that are read from the log in each chunk. Default is infinity , which means that all the terms contained in the 8K chunk are read. If less than N terms are returned, this does not necessarily mean that end of file is reached. The chunk function returns a tuple {Continuation2, Terms} , where Terms is a list of terms found in the log. Continuation2 is yet another continuation which must be passed on into any subsequent calls to chunk . With a series of calls to chunk it is then possi- ble to extract all terms from a log. The chunk function returns a tuple {Continuation2, Terms, Badbytes} if the log is opened in read only mode and the read chunk is corrupt. Badbytes indicates the number of non-Erlang terms found in the chunk. Note also that the log is not repaired. chunk returns {Continuation2, eof} when the end of the log is reached, and {error, Reason} if an error occurs. The returned continuation may or may not be valid in the next call to chunk . This is because the log may wrap and delete the file into which the continuation points. To make sure this does not happen, the log can be blocked during the search. close(Continuation) -> ok Types Continuation = continuation() This function closes a log file properly. open(Filename) -> OpenRet open(Filename, N) -> OpenRet Types File = string() | atom() N = integer() OpenRet = {ok, Continuation} | {error, Reason} Continuation = continuation() Filename specifies the name of the file which is to be read. N specifies the index of the file which is to be read. If N is omitted the whole wrap log file will be read; if it is specified only the specified index file will be read. The open function returns {ok, Continuation} if the log/index file was successfully opened. The Continuation is to be used when chunking or closing the file. The function returns {error, Reason} for all errors. BUGS
This version of the wrap_log_reader does not detect if the disk_log wraps to a new index file between a wrap_log_reader:open and the first wrap_log_reader:chunk . In this case the chuck will actually read the last logged items in the log file, because the opened index file was truncated by the disk_log . SEE ALSO
disk_log(3erl) Ericsson AB kernel 2.14.3 wrap_log_reader(3erl)