Hello, I am using SQLite on an embedded system that the user will power off at any time (i.e. there is never a clean shut down). The system contains sensors and uses a C program with the SQLite library. The sensor data is saved to an in-memory database every second. Every 10 seconds, the program saves any new data to a database on disk, a USB flash drive.
Because of the nature of the system usage, it is likely that SQLite will be in the middle of a transaction when the system loses power. This leaves behind a hot journal file with the "-journal" extension. When the system starts up, I would like to browse through all the files in the USB disk and find "-journal" files so that the program can roll back the final transaction that occurred when the system was powered off. I was under the impression (http://www.sqlite.org/tempfiles.html) that all I needed to do was open the base file (without the "-journal" extension) with sqlite3_open_v2() and then close the database in order to clean up the hot journal. However, this does not appear to work the way I expected it to. The "-journal" file remains. Pasted below is the function (clean_tmp_files()) that I created to help me with this task. Given a directory as an argument, the function finds all the "-journal" files and tries to open and close the underlying database. You can treat the log_debug() and log_verbose() functions as if they are printf(). These are just part of my program's logging mechanism. I am using SQLite version 3.7.16.2. #include <glob.h> #include <stdio.h> #include "sqlite3.h" /** Returns true if the file specified by filename exists. */ static bool file_exists(char *filename); /** Clean up the temporary database files stored in dir. These files * are usually residual after an unclean shutdown, which happens all * the time on embedded systems. */ static void clean_tmp_files(const char *dir); <... other code in my .c file ...> static void clean_tmp_files(const char *dir) { char match_str[1024]; char base_db_str[1024]; glob_t globber; snprintf(match_str, 1024, "%s/%s", dir, "*-journal"); if (glob(match_str, 0, NULL, &globber) == 0) { unsigned int i; for (i=0; i<globber.gl_pathc; i++) { log_debug("Cleaning up database temporary file %s\n", globber.gl_pathv[i]); snprintf(base_db_str, strlen(globber.gl_pathv[i]) - strlen("-journal") + 1, globber.gl_pathv[i]); log_verbose("Want to clean it up by opening and closing %s\n", base_db_str); if (file_exists(base_db_str)) { sqlite3 *db; int err; log_debug("Opening and closing %s\n", base_db_str); err = sqlite3_open_v2(base_db_str, &db, SQLITE_OPEN_READWRITE, NULL); if (err < 0) { log_error("%s Sqlite open error: %s\n", __FUNCTION__, sqlite3_errstr(err)); } sqlite3_close(db); } else { log_warn("No base db file exists for %s. Deleting the temporary file outright.\n", globber.gl_pathv[i]); remove(globber.gl_pathv[i]); } } } globfree(&globber); } static bool file_exists(char *filename) { bool ret = false; FILE *test = fopen(filename, "r"); if (test != NULL) { ret = true; fclose(test); } return ret; } I appreciate any help that you can offer. And kudos to the developers for this tool--it is amazing!! Thank you, Mike Foss _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
