C Error Log
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How To Create A Log File In C
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C++ Log File Class
them; it only takes a minute: Sign up storing logs/error message on C programming up vote 3 down vote favorite When an error occurs, I would like my C code to store the error before exiting the program. Is it advised to store the stderr to a file (e.g., /home/logs.txt) or would it be advised to use a different c logger example method to keep the logs/error report (considering the programming environment is Linux). E.g., for the code below, how I could apply the method to store the logs/error message on /home/log.txt or /home/log FILE *fp1; fp1 = fopen("/sys/class/gpio/export","w"); if(fp1 == NULL){ fprintf(stderr, "errno:%s - opening GPIO136 failed - line 739\n ", strerror(errno)); close(fp1); exit(1); } Thank you. c linux error-handling posix stderr share|improve this question asked Apr 20 '13 at 3:13 sven 31011129 1 The call to close() is wrong, as it's meant for file descriptors not for file handles. You should have reveived a compiler warning/error here, as you pass a pointer to where an integer is expected. However calling fclose() would be redundant, as the file had not been opened, which is indicated by fp1 being NULL. –alk Apr 20 '13 at 8:59 Thank you alk, I will fix it on my code –sven Apr 20 '13 at 13:01 add a comment| 2 Answers 2 active oldest votes up vote 3 down vote accepted If stderr is always used to pr
Logging Callback 2. Interface Details 3. Variety of Error Messages 4. Summary Overview SQLite can be configured to invoke a callback function containing an error code and a terse error message whenever anomalies occur. This mechanism is
How To Create Log File In C Programming
very helpful in tracking obscure problems that occur rarely and in the field. Application logging in c++ developers are encouraged to take advantage of the error logging facility of SQLite in their products, as it is very low log file c++ code CPU and memory cost but can be a huge aid for debugging. 1. Setting Up The Error Logging Callback There can only be a single error logging callback per process. The error logging callback http://stackoverflow.com/questions/16116143/storing-logs-error-message-on-c-programming is registered at start-time using C-code similar to the following: sqlite3_config(SQLITE_CONFIG_LOG, errorLogCallback, pData); The error logger callback function might look something like this: void errorLogCallback(void *pArg, int iErrCode, const char *zMsg){ fprintf(stderr, "(%d) %s\n", iErrCode, zMsg); } The example above illustrates the signature of the error logger callback. However, in an embedded application, one usually does not print messages on stderr. Instead, one might store the messages in a preallocated https://www.sqlite.org/errlog.html circular buffer where they can be accessed when diagnostic information is needed during debugging. Or perhaps the messages can be sent to Syslog. Somehow, the messages need to be stored where they are accessible to developers, not displayed to end users. Do not misunderstand: There is nothing technically wrong with displaying the error logger messages to end users. The messages do not contain sensitive or private information that must be protected from unauthorized viewing. Rather the messages are technical in nature and are not useful or meaningful to the typical end user. The messages coming from the error logger are intended for database geeks. Display them accordingly. 2. Interface Details The third argument to the sqlite3_config(SQLITE_CONFIG_LOG,...) interface (the "pData" argument in the example above) is a pointer to arbitrary data. SQLite passes this pointer through to the first argument of the error logger callback. The pointer can be used to pass application-specific setup or state information, if desired. Or it can simply be a NULL pointer which is ignored by the callback. The second argument to the error logger callback is an integer extended error code. The third argument to the error logger is the text of the error message. The error message text is stored in a
known as exception handling). By convention, the programmer is expected to prevent errors from occurring in the first place, and test return values from functions. For example, -1 and https://en.wikibooks.org/wiki/C_Programming/Error_handling NULL are used in several functions such as socket() (Unix socket programming) or malloc() respectively to indicate problems that the programmer should be aware about. In a worst case scenario where there is an unavoidable error and no way to recover from it, a C programmer usually tries to log the error and "gracefully" terminate the program. There is an external variable called log file "errno", accessible by the programs after including