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#include <stdio.h> |
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#include <time.h> |
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#include <unistd.h> |
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#include <stdlib.h> |
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#include <string.h> |
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|
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/* GetNextID - returns the next serial number for given file |
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* |
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* Uses flock on a file that contains the previous |
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* ID. Locks the file, reads prev number, writes next number, removes lock. |
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* returns a single line on stdout containing the incremented number. |
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* Format is <fixed part>-<date>-<sequence number>. |
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* |
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* To call with a new file and/or new fixed-part call with 2 args, <filename> <fixed_part> |
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* To simply update an existing ID number part of an existing ID file, call with just <filename> |
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*/ |
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|
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void static getlock(FILE *fp, char *fname) |
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{ |
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int sleeps; |
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for(sleeps=0; lockf(fileno(fp),F_TLOCK,0); sleeps++) |
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{ |
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if (sleeps >= 20) |
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{ |
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fprintf(stderr,"Lock stuck on %s, GetNextID failed.\n", fname); |
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exit(1); |
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} |
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sleep(1); |
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} |
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return; |
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} |
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|
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int main(int argc, char **argv) |
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{ |
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char fname[1024]; |
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int NextIDsn; |
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int nread; |
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int old_date, new_date; |
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int year, month, day; |
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char fixedpart[100]; |
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char NextID[100]; |
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FILE *fp; |
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struct tm *now; |
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time_t nowtime; |
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|
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if (argc < 2) |
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{ |
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fprintf(stderr, "GetNextID failed, needs filename.\n"); |
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exit(1); |
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} |
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strncpy(fname, argv[1], 1000); |
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|
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if (argc == 3) |
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{ |
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strcpy(fixedpart, argv[2]); |
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NextIDsn = 0; |
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old_date = 0; |
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fp = fopen(fname, "w"); |
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getlock(fp, fname); |
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} |
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else |
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{ |
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fp = fopen(fname, "r+"); |
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if (!fp) |
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{ |
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fprintf(stderr, "GetNextID failed to open sn file, %s.\n", fname); |
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exit(1); |
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} |
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getlock(fp, fname); |
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|
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nread = fscanf(fp,"%[^-]-%d-%d",fixedpart,&old_date,&NextIDsn); |
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if (nread != 3) |
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{ |
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fprintf(stderr,"GetNextID failed. found %d instead of 3 fields in %s\n", nread, fname); |
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exit(1); |
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} |
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} |
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|
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nowtime = time(0); |
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now = gmtime(&nowtime); |
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new_date = 10000*(now->tm_year+1900) + 100*(now->tm_mon+1) + now->tm_mday; |
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if (old_date != new_date) |
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{ |
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FILE *history; |
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strcat(fname, ".history"); |
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history = fopen(fname, "a"); |
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fprintf(history,"%s-%d-%05d\n", fixedpart, old_date, NextIDsn); |
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fclose(history); |
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NextIDsn = 1; |
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} |
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else |
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NextIDsn += 1; |
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rewind(fp); |
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sprintf(NextID,"%s-%d-%05d", fixedpart, new_date, NextIDsn); |
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|
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fprintf(fp,"%s\n",NextID); |
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rewind(fp); |
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lockf(fileno(fp),F_ULOCK,0); |
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fclose(fp); |
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printf("%s\n",NextID); |
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} |
